https://daniele-michelin.com/blog/betrugs-radar-aktuelle-phishing-warnungen/ https://daniele-michelin.com/assets/og/betrugs-radar-aktuelle-phishing-warnungen.png Betrugs-Radar: aktuelle Phishing-Mails und Fake-SMS erkennen Mein neues Betrugs-Radar sammelt aktuelle Betrugsmaschen, erklärt sie verständlich und sagt, was zu tun ist. So funktioniert es, und so erkennst du Betrug. https://daniele-michelin.com/blog/dns-umzug-ohne-ausfall/ https://daniele-michelin.com/assets/og/dns-umzug-ohne-ausfall.png DNS-Umzug ohne Ausfall: TTL, Zonen-Export, Checkliste Hosting oder DNS-Anbieter wechseln, ohne dass Website und E-Mail ausfallen: TTL senken, Zone exportieren statt abtippen, vorab testen — mit Checkliste. https://daniele-michelin.com/blog/e-mail-faelschung-ranking-102-domains/ https://daniele-michelin.com/assets/og/e-mail-faelschung-ranking-102-domains.png Lassen sich diese Domains fälschen? SPF und DMARC im Test SPF, DMARC und MTA-STS von 102 bekannten Domains: 59 weisen gefälschte Mails ab, 21 beobachten nur mit p=none, 6 haben kein DMARC. Banken, Deutschland, Italien. https://daniele-michelin.com/blog/e-mail-spam-spf-dkim-dmarc/ https://daniele-michelin.com/assets/og/e-mail-spam-spf-dkim-dmarc.png SPF, DKIM und DMARC erklärt: Mails nicht mehr im Spam SPF, DKIM und DMARC einfach erklärt: was jedes prüft, warum Mails trotz SPF im Spam landen, wie man Header liest — mit Tabelle, Befehlen und Checkliste. https://daniele-michelin.com/blog/fallnotiz-linux-no-space-left/ https://daniele-michelin.com/assets/og/fallnotiz-linux-no-space-left.png Fallnotiz: No space left on device trotz freiem Speicher Fallnotiz: „No space left on device“, aber df zeigt freien Platz? Meist sind Inodes voll oder gelöschte Dateien noch offen. Diagnose mit df -i, lsof +L1… https://daniele-michelin.com/blog/fallnotiz-nextcloud-423-locked/ https://daniele-michelin.com/assets/og/fallnotiz-nextcloud-423-locked.png Fallnotiz: Nextcloud „File is locked“ (423 Locked) beheben Fallnotiz: Nextcloud meldet „is locked“ oder 423 Locked? Hängende Dateisperren nach Abbrüchen. So prüfen Sie Redis-Locking, Cron und entfernen alte Locks… https://daniele-michelin.com/blog/halloween-token-monster-bild-gegen-video/ https://daniele-michelin.com/assets/og/halloween-token-monster-bild-gegen-video.png Halloween: Das Token-Monster frisst lieber Videos als Bilder Ein Halloween-Bild oder ein kurzes KI-Video? Ein konkretes Beispiel mit 1.120 gegen 28.960 Output-Token – und warum der Vergleich nicht die ganze Rechnung ist. https://daniele-michelin.com/blog/ki-assistent-fuer-die-eigene-website/ https://daniele-michelin.com/assets/og/ki-assistent-fuer-die-eigene-website.png KI-Assistent für die eigene Website: Chat und Sprache, lokal gehostet Aus einem lokalen KI-Telefon-Empfang wurde ein Assistent für meine Website: Widget, nginx-Proxy, Sprache auf dem Mac, Terminbuchung, Datenschutz. https://daniele-michelin.com/blog/n8n-daten-orakel/ https://daniele-michelin.com/assets/og/n8n-daten-orakel.png Just for fun: ein n8n-Orakel aus Live-Daten Ein n8n-Workflow zum Spaß: drei Live-Datenquellen parallel, Mondphase per Code, eine KI als Wahrsagerin und Tarotkarten zum Teilen. Mit Download. https://daniele-michelin.com/blog/n8n-erd-orchester/ https://daniele-michelin.com/assets/og/n8n-erd-orchester.png Erd-Orchester: Erdbeben und Sonnenaktivität werden Musik Das Erd-Orchester macht aus USGS-Erdbeben und dem NOAA-Kp-Index Töne und Animationen. Live ausprobieren, musikalische Regeln verstehen, n8n-Workflow laden. https://daniele-michelin.com/blog/n8n-ki-talkshow/ https://daniele-michelin.com/assets/og/n8n-ki-talkshow.png Die KI-Talkshow: 5 KIs besprechen deine Website Hackerin, SEO-Guru, Designerin, Oma Erna und ein ungeduldiger Kunde besprechen deine Website. Fünf KIs parallel in n8n, mit Fallback und Tipps. https://daniele-michelin.com/blog/n8n-link-galaxie/ https://daniele-michelin.com/assets/og/n8n-link-galaxie.png Link-Galaxie: interne Links als 3D-Karte Domain eingeben, Galaxie drehen: defekte Links als Schwarze Löcher, verwaiste Seiten als Planeten. n8n-Workflow mit Crawler, KI und Download. https://daniele-michelin.com/blog/n8n-mission-control/ https://daniele-michelin.com/assets/og/n8n-mission-control.png Mission Control: ein n8n-Spiel zur Incident Response Drei Entscheidungen in 90 Sekunden zu einer wirklich ausgenutzten CISA-Lücke. Lies, wie Mission Control entstand, und lade den n8n-Workflow herunter. https://daniele-michelin.com/blog/n8n-nextcloud-buero-morgen/ https://daniele-michelin.com/assets/og/n8n-nextcloud-buero-morgen.png Büro-Morgen: n8n schreibt in Nextcloud Ein Klick: n8n liest Kalender, Deck, Dateien und Talk eines Demo-Büros in Nextcloud, eine KI schreibt das Briefing, n8n legt alles wirklich an. https://daniele-michelin.com/blog/n8n-orbit-postkarte/ https://daniele-michelin.com/assets/og/n8n-orbit-postkarte.png n8n-Showcase: eine Postkarte aus dem Orbit Knopf drücken, Postkarte erhalten: n8n fragt die ISS-Position ab, holt das NASA-Satellitenbild darunter und lässt eine KI schreiben. Mit Workflow-Download. https://daniele-michelin.com/blog/n8n-vorgestellt-internet-puls/ https://daniele-michelin.com/assets/og/n8n-vorgestellt-internet-puls.png n8n vorgestellt: ein Workflow, der dem Internet den Puls fühlt Was n8n ist, warum ich es selbst hoste und ein Beispiel-Workflow: 7 Quellen, eine KI, per Knopfdruck live auf einer Seite. Mit Download zum Importieren. https://daniele-michelin.com/blog/n8n-website-dna/ https://daniele-michelin.com/assets/og/n8n-website-dna.png Website-DNA: Fremd-Code finden mit n8n Domain eingeben, Doppelhelix ansehen: eigener Code, Drittanbieter, Bibliotheken mit bekannten CVEs und Cookies. n8n-Workflow mit OSV.dev und KI. https://daniele-michelin.com/blog/n8n-website-stadt/ https://daniele-michelin.com/assets/og/n8n-website-stadt.png Deine Website als Stadt: ein n8n-Workflow Domain eingeben, Stadt in 3D erkunden: Bereiche werden Viertel, Unterseiten Hochhäuser, Header Wachtürme. n8n-Workflow mit KI und Download. https://daniele-michelin.com/blog/n8n-woche-21-polarlicht-radar/ https://daniele-michelin.com/assets/og/n8n-woche-21-polarlicht-radar.png n8n #21: Polarlicht-Radar mit NOAA-Kp-Index Alle 15 Minuten den Kp-Index der NOAA lesen und nur bei steigender geomagnetischer Aktivität eine Push-Nachricht senden. Ohne Schlüssel und ohne Doppelalarm. https://daniele-michelin.com/blog/nextcloud-collabora-code-luecke-cve-2026-110447/ https://daniele-michelin.com/assets/og/nextcloud-collabora-code-luecke-cve-2026-110447.png Nextcloud CODE-Lücke CVE-2026-110447: prüfen, updaten, entfernen CVE-2026-110447 erlaubt Befehle auf Nextcloud-Servern mit der Collabora-CODE-App. So prüfst du, aktualisierst oder entfernst die App und suchst nach Web-Shells. https://daniele-michelin.com/blog/nextcloud-dateien-nicht-sichtbar-files-scan/ https://daniele-michelin.com/assets/og/nextcloud-dateien-nicht-sichtbar-files-scan.png Nextcloud zeigt kopierte Dateien nicht: occ files:scan Dateien direkt ins Nextcloud-Datenverzeichnis kopiert, aber die Weboberfläche bleibt leer? Warum das passiert und wie occ files:scan das behebt. https://daniele-michelin.com/blog/nextcloud-extern-pruefen/ https://daniele-michelin.com/assets/og/nextcloud-extern-pruefen.png Nextcloud vom externen Netz prüfen: Version, EOL, offene Pfade Ein Tool, das die eigene Nextcloud aus dem echten Netz bewertet: Version, End of Life, exponierte Pfade (config, data, .htaccess) und Security-Header. Ohne Login. https://daniele-michelin.com/blog/nextcloud-saml-oidc-fehler/ https://daniele-michelin.com/assets/og/nextcloud-saml-oidc-fehler.png Nextcloud SAML/OIDC: 8 häufige SSO-Fehler und Lösungen Redirect-Schleifen, Zeitabweichung, falsches UID-Mapping, doppelte Konten: die häufigsten SSO-Fehler in Nextcloud und ihre Lösungen. https://daniele-michelin.com/blog/nginx-sicherheitsluecken-oktober-2026/ https://daniele-michelin.com/assets/og/nginx-sicherheitsluecken-oktober-2026.png NGINX: drei kritische Lücken, Update auf 1.30.6 / 1.31.7 NGINX-Fix in 1.30.6 und 1.31.7 (Plus 37.1.0.1, 37.0.5.1): welche Konfigurationen betroffen sind, wie du sie prüfst und Container aktualisierst. https://daniele-michelin.com/blog/php-sicherheitsupdate-php2shell/ https://daniele-michelin.com/assets/og/php-sicherheitsupdate-php2shell.png PHP2Shell patchen: Plesk, Synology, Webhosting, Server Zwei kritische PHP-Lücken, Fix in 8.5.12, 8.4.27, 8.3.36, 8.2.35: was auf Plesk, Synology, Webhosting, Docker und eigenen Servern zu tun ist. https://daniele-michelin.com/blog/php2shell-eine-woche-danach-kernel-luecke/ https://daniele-michelin.com/assets/og/php2shell-eine-woche-danach-kernel-luecke.png PHP2Shell nach einer Woche: Angriffe, Kernel-Lücke PHP2Shell wird ausgenutzt und steht auf der CISA-Liste. Eine Linux-Kernel-Lücke (CVE-2026-46300) macht daraus Root. Die Lage in Grafiken und was Sie heute prüfen. https://daniele-michelin.com/blog/php2shell-notloesung-php-ini/ https://daniele-michelin.com/assets/og/php2shell-notloesung-php-ini.png PHP2Shell ohne Update entschärfen: Synology, Plesk, NAS Noch kein PHP-Update, z. B. auf Synology? Drei php.ini-Einstellungen verkleinern die Angriffsfläche von PHP2Shell — für Web Station, Plesk und Server. https://daniele-michelin.com/blog/root-cause-analyse-im-support/ https://daniele-michelin.com/assets/og/root-cause-analyse-im-support.png Root-Cause-Analyse im Support: Symptom ≠ Ursache Ein Workaround schließt das Ticket, erst die Ursachenanalyse verhindert das nächste. Wie man im 2nd/3rd-Level vom Symptom zur eigentlichen Ursache kommt. https://daniele-michelin.com/blog/sicherheits-header-57-websites/ https://daniele-michelin.com/assets/og/sicherheits-header-57-websites.png Wir haben die Sicherheits-Header von 57 Websites bewertet Test von 57 bekannten Websites: HSTS ist verbreitet, CSP nicht. Ergebnisse je Header, die vier Seiten mit Note A und wie man die Zahlen fair liest. https://daniele-michelin.com/blog/sicherheits-header-starter-set/ https://daniele-michelin.com/assets/og/sicherheits-header-starter-set.png HTTP-Sicherheits-Header: Starter-Set für nginx HSTS, CSP, X-Content-Type-Options, Referrer-Policy, Permissions-Policy: Was jeder Header bewirkt, ein nginx-Starter-Set zum Kopieren und wie man es testet. https://daniele-michelin.com/blog/website-sicherheits-zeugnis/ https://daniele-michelin.com/assets/og/website-sicherheits-zeugnis.png Ein Schulzeugnis für die Sicherheit Ihrer Website Domain eingeben, Zeugnis bekommen: Noten für Sicherheits-Header, SPF/DMARC und TLS-Zertifikat, eine Gesamtnote und Bemerkungen vom Lehrer. Kostenlos. https://daniele-michelin.com/demo/opscope/ https://daniele-michelin.com/assets/og/projects/opscope-demo-de.png OPSCOPE Live-Demo: Server-Diagnose im Terminal · Daniele Michelin Aufzeichnung von OPSCOPE, meinem schreibgeschützten Bash-Toolkit für Linux-Server: ein simulierter Vorfall von der Diagnose bis zum Bericht. https://daniele-michelin.com/en/ai-talk-show/ https://daniele-michelin.com/assets/og/ki-talkshow.png?v=1 The AI talk show: 5 AI guests discuss your website Enter a domain: a hacker, an SEO guru, a designer, Grandma Erna and an impatient customer discuss your website live. n8n, AI and concrete tips. https://daniele-michelin.com/en/blog/ai-assistant-for-your-own-website/ https://daniele-michelin.com/assets/og/ai-assistant-for-your-own-website.png An AI assistant for your own website: chat and voice, self-hosted How a local AI phone receptionist became an assistant for my website: widget, nginx proxy, voice on my Mac, appointment booking, privacy. https://daniele-michelin.com/en/blog/checking-nextcloud-from-the-outside/ https://daniele-michelin.com/assets/og/checking-nextcloud-from-the-outside.png Checking your Nextcloud from the outside: version, EOL, exposed paths A tool that scores your own Nextcloud from the real network: version, end of life, exposed paths (config, data, .htaccess) and security headers. No login. https://daniele-michelin.com/en/blog/dns-migration-without-downtime/ https://daniele-michelin.com/assets/og/dns-migration-without-downtime.png DNS migration without downtime: TTL, zone export, checklist Switch hosting or DNS provider without losing website or e-mail: lower the TTL, export the zone instead of retyping it, test before the cutover. https://daniele-michelin.com/en/blog/email-spam-spf-dkim-dmarc/ https://daniele-michelin.com/assets/og/email-spam-spf-dkim-dmarc.png SPF, DKIM and DMARC explained: stop mail landing in spam SPF, DKIM and DMARC explained simply: what each checks, why mail lands in spam although SPF passes, how to read headers — with a table and checklist. https://daniele-michelin.com/en/blog/email-spoofing-ranking-102-domains/ https://daniele-michelin.com/assets/og/email-spoofing-ranking-102-domains.png Can these domains be spoofed? SPF and DMARC of 102 sites SPF, DMARC and MTA-STS of 102 well-known domains: 59 reject forged mail, 21 only monitor with p=none, 6 have no DMARC. Banks, Germany and Italy compared. https://daniele-michelin.com/en/blog/halloween-token-monster-image-vs-video/ https://daniele-michelin.com/assets/og/halloween-token-monster-image-vs-video.png Halloween: the token monster prefers video to still images A Halloween still or a short AI video? One concrete example: 1,120 versus 28,960 output tokens, and why that ratio is not the whole cost story. https://daniele-michelin.com/en/blog/incident-note-linux-no-space-left/ https://daniele-michelin.com/assets/og/incident-note-linux-no-space-left.png Incident note: No space left on device despite free space Incident note: No space left on device but df shows free space? Usually inodes are exhausted or deleted files are still open. Diagnose with df -i and lsof… https://daniele-michelin.com/en/blog/incident-note-nextcloud-423-locked/ https://daniele-michelin.com/assets/og/incident-note-nextcloud-423-locked.png Incident note: Nextcloud "file is locked" (423 Locked): fix Incident note: Nextcloud says is locked or 423 Locked? Stale file locks after aborted requests. How to check Redis locking and cron, and clear old locks… https://daniele-michelin.com/en/blog/n8n-ai-talk-show/ https://daniele-michelin.com/assets/og/n8n-ai-talk-show.png The AI talk show: 5 AIs discuss your website A hacker, an SEO guru, a designer, Grandma Erna and an impatient customer discuss your website. Five AIs in parallel in n8n, with fallback and tips. https://daniele-michelin.com/en/blog/n8n-data-oracle/ https://daniele-michelin.com/assets/og/n8n-data-oracle.png Just for fun: an n8n oracle built on live data An n8n workflow for fun: three live data sources in parallel, the moon phase in a Code node, an AI fortune teller and shareable tarot cards. Download included. https://daniele-michelin.com/en/blog/n8n-earth-orchestra/ https://daniele-michelin.com/assets/og/n8n-earth-orchestra.png Earth Orchestra: earthquakes and solar activity become music Earth Orchestra turns USGS earthquakes and NOAA's Kp index into notes and animation. Try the live demo, see the musical rules and download the n8n workflow. https://daniele-michelin.com/en/blog/n8n-introduced-internet-pulse/ https://daniele-michelin.com/assets/og/n8n-introduced-internet-pulse.png n8n introduced: a workflow that takes the internet's pulse What n8n is, why I self-host it, and an example workflow: 7 sources, one AI, live on a page at the press of a button. With a download to import it yourself. https://daniele-michelin.com/en/blog/n8n-link-galaxy/ https://daniele-michelin.com/assets/og/n8n-link-galaxy.png Link galaxy: internal links as a 3D map Enter a domain, spin the galaxy: broken links become black holes, orphan pages drifting planets. An n8n workflow with a crawler, AI and a download. https://daniele-michelin.com/en/blog/n8n-nextcloud-office-morning/ https://daniele-michelin.com/assets/og/n8n-nextcloud-office-morning.png Office morning: n8n writes into Nextcloud One click: n8n reads the calendar, Deck, files and Talk of a demo office in Nextcloud, an AI writes the briefing, n8n really creates it all. https://daniele-michelin.com/en/blog/n8n-orbit-postcard/ https://daniele-michelin.com/assets/og/n8n-orbit-postcard.png n8n showcase: a postcard from orbit Press a button, get a postcard: n8n finds the ISS, fetches the NASA satellite image of the spot below and lets an AI write. With the workflow to download. https://daniele-michelin.com/en/blog/n8n-website-city/ https://daniele-michelin.com/assets/og/n8n-website-city.png Your website as a city: an n8n workflow Enter a domain, explore a 3D city: sections become districts, subpages high-rises, headers watchtowers. An n8n workflow with AI and a download. https://daniele-michelin.com/en/blog/n8n-website-dna-scan/ https://daniele-michelin.com/assets/og/n8n-website-dna-scan.png Website DNA: find third-party code with n8n Enter a domain, watch the double helix: own code, third parties, libraries with known CVEs and cookies. An n8n workflow with OSV.dev and AI. https://daniele-michelin.com/en/blog/n8n-week-21-aurora-radar/ https://daniele-michelin.com/assets/og/n8n-week-21-aurora-radar.png n8n #21: aurora radar with NOAA Kp index Read NOAA's Kp index every 15 minutes and send a push only when geomagnetic activity rises. No API key and no duplicate alerts. https://daniele-michelin.com/en/blog/nextcloud-collabora-code-flaw-cve-2026-110447/ https://daniele-michelin.com/assets/og/nextcloud-collabora-code-flaw-cve-2026-110447.png Nextcloud CODE flaw CVE-2026-110447: check, update, remove CVE-2026-110447 lets attackers run commands on Nextcloud servers with the built-in CODE app. How to check, update or remove it and look for web shells. https://daniele-michelin.com/en/blog/nextcloud-files-not-showing-files-scan/ https://daniele-michelin.com/assets/og/nextcloud-files-not-showing-files-scan.png Nextcloud doesn't show copied files: occ files:scan Copied files straight into the Nextcloud data directory but the web UI stays empty? Why it happens and how occ files:scan fixes it. https://daniele-michelin.com/en/blog/nextcloud-saml-oidc-errors/ https://daniele-michelin.com/assets/og/nextcloud-saml-oidc-errors.png Nextcloud SSO not working? 8 SAML/OIDC errors and fixes Redirect loop, clock skew, wrong UID, duplicate accounts, missing groups: 8 SAML/OIDC errors from Nextcloud support — each with the cause and the fix. https://daniele-michelin.com/en/blog/nginx-vulnerabilities-october-2026/ https://daniele-michelin.com/assets/og/nginx-vulnerabilities-october-2026.png NGINX: three critical flaws, update to 1.30.6 / 1.31.7 NGINX fix in 1.30.6 and 1.31.7 (Plus 37.1.0.1, 37.0.5.1): which configurations are affected, how to check them and how to update containers. https://daniele-michelin.com/en/blog/php-emergency-patch-php2shell/ https://daniele-michelin.com/assets/og/php-emergency-patch-php2shell.png PHP2Shell patch: Plesk, Synology, shared hosting, servers Two critical PHP flaws, fixed in 8.5.12, 8.4.27, 8.3.36 and 8.2.35: what to do on Plesk, Synology, shared hosting, Docker and your own servers. https://daniele-michelin.com/en/blog/php2shell-one-week-later-kernel-flaw/ https://daniele-michelin.com/assets/og/php2shell-one-week-later-kernel-flaw.png PHP2Shell one week on: attacks and a kernel flaw PHP2Shell is exploited and on CISA's list. Now a Linux kernel flaw (CVE-2026-46300) can turn it into root. The facts in charts, and what to check today. https://daniele-michelin.com/en/blog/php2shell-workaround-php-ini/ https://daniele-michelin.com/assets/og/php2shell-workaround-php-ini.png PHP2Shell on Synology without an update: php.ini fix No PHP update yet on Synology? Three php.ini settings shrink the PHP2Shell attack surface — step by step for Web Station, Plesk and your own servers. https://daniele-michelin.com/en/blog/root-cause-analysis-in-support/ https://daniele-michelin.com/assets/og/root-cause-analysis-in-support.png Root cause analysis in support: symptom ≠ cause A workaround closes the ticket; only root cause analysis prevents the next one. How 2nd/3rd-level support gets from the symptom to the actual cause. https://daniele-michelin.com/en/blog/scam-radar-current-phishing-warnings/ https://daniele-michelin.com/assets/og/scam-radar-current-phishing-warnings.png Scam radar: spot current phishing emails and fake texts My new scam radar collects current scams, explains them in plain words and says what to do. How it works, and how to spot a scam before you click. https://daniele-michelin.com/en/blog/security-headers-57-websites/ https://daniele-michelin.com/assets/og/security-headers-57-websites.png We graded the security headers of 57 big websites A scan of 57 well-known sites: HSTS is common, CSP is not. Results by header, the four sites with grade A, and how to read the numbers fairly. https://daniele-michelin.com/en/blog/security-headers-starter-set/ https://daniele-michelin.com/assets/og/security-headers-starter-set.png HTTP security headers: a safe starter set for nginx HSTS, CSP, X-Content-Type-Options, Referrer-Policy, Permissions-Policy: what each security header does, a copy-paste nginx starter set, and how to test it. https://daniele-michelin.com/en/blog/website-security-report-card/ https://daniele-michelin.com/assets/og/website-security-report-card.png A school report card for your website's security Type a domain and get a report card: grades for security headers, SPF/DMARC and the TLS certificate, an overall grade and teacher remarks. Free. https://daniele-michelin.com/en/cheat-sheets/dig-cheat-sheet/ https://daniele-michelin.com/assets/og/kb/en-c-dig.png dig Cheat Sheet – DNS Lookup Commands · Daniele Michelin dig commands for DNS troubleshooting: A, MX, TXT, CAA, +short, +trace, reverse lookups, DNSSEC, SPF/DKIM/DMARC checks and authoritative queries. https://daniele-michelin.com/en/cheat-sheets/docker-cheat-sheet/ https://daniele-michelin.com/assets/og/kb/en-c-docker.png Docker Cheat Sheet – Commands for Admins · Daniele Michelin Essential Docker commands: images, containers, logs, exec, volumes, networks, Compose, cleaning up with prune and resource limits for admins. https://daniele-michelin.com/en/cheat-sheets/git-cheat-sheet/ https://daniele-michelin.com/assets/og/kb/en-c-git.png Git Cheat Sheet – Everyday Commands & Rescue · Daniele Michelin Essential Git commands: status, log, stash, rebase, reflog recovery, undo variants, remotes and bisect for everyday work and emergencies. https://daniele-michelin.com/en/cheat-sheets/ https://daniele-michelin.com/assets/og/kb/en-hub-cheats.png Admin cheat sheets: nginx, Docker, Git, systemd & more Searchable command references for Nextcloud occ, dig, journalctl, openssl, nginx, systemctl, Docker and Git — with copy buttons and warnings on risky commands. https://daniele-michelin.com/en/cheat-sheets/journalctl-cheat-sheet/ https://daniele-michelin.com/assets/og/kb/en-c-journalctl.png journalctl Cheat Sheet – systemd Log Commands · Daniele Michelin journalctl commands for troubleshooting: filter logs by unit, boot, time and priority, follow live, JSON output and keep journal disk usage in check. https://daniele-michelin.com/en/cheat-sheets/nextcloud-occ-cheat-sheet/ https://daniele-michelin.com/assets/og/kb/en-c-occ.png Nextcloud occ Commands: Cheat Sheet with Copy-Paste Examples Copy-paste Nextcloud occ commands for admins: maintenance mode, files:scan, users, apps, missing DB indices, cron, trash bin cleanup and 2FA. https://daniele-michelin.com/en/cheat-sheets/nginx-cheat-sheet/ https://daniele-michelin.com/assets/og/kb/en-c-nginx.png nginx Cheat Sheet – Commands & Config Snippets · Daniele Michelin Essential nginx commands and config snippets for admins: test and reload, logs, redirects, proxy_pass, rate limiting, gzip and debugging. https://daniele-michelin.com/en/cheat-sheets/openssl-cheat-sheet/ https://daniele-michelin.com/assets/og/kb/en-c-openssl.png OpenSSL Cheat Sheet – TLS & Certificate Commands · Daniele Michelin OpenSSL commands for TLS troubleshooting: check certificate chain and expiry, create a CSR, match key and cert, convert PEM/DER/PFX, test STARTTLS. https://daniele-michelin.com/en/cheat-sheets/systemctl-cheat-sheet/ https://daniele-michelin.com/assets/og/kb/en-c-systemctl.png systemctl Cheat Sheet – systemd Commands · Daniele Michelin Essential systemctl commands: status, start, restart, enable, timers, drop-in overrides, systemd-analyze and targets for Linux admins. https://daniele-michelin.com/en/compare/http-01-vs-dns-01/ https://daniele-michelin.com/assets/og/kb/en-v-http-01-vs-dns-01.png Let's Encrypt: HTTP-01 vs DNS-01 · Daniele Michelin HTTP-01 or DNS-01 challenge for Let's Encrypt? Wildcards, internal hosts, port 80, DNS API access and typical validation failures compared. https://daniele-michelin.com/en/compare/ https://daniele-michelin.com/assets/og/kb/en-hub-compare.png Tech comparisons for admins: SAML, Nextcloud, DNS · Daniele Michelin Honest comparisons from operations: SAML or OIDC, Nextcloud or Seafile, HTTP-01 or DNS-01, cron or systemd timers — which one fits when. https://daniele-michelin.com/en/compare/nextcloud-aio-vs-manual-install/ https://daniele-michelin.com/assets/og/kb/en-v-nextcloud-aio-vs-manual.png Nextcloud AIO vs Manual Installation · Daniele Michelin Nextcloud All-in-One or a classic setup with web server, PHP-FPM and database? Effort, control, updates, backup and troubleshooting compared honestly. https://daniele-michelin.com/en/compare/nextcloud-s3-vs-nfs/ https://daniele-michelin.com/assets/og/kb/en-v-s3-vs-nfs-nextcloud.png Nextcloud: S3 vs NFS as Primary Storage · Daniele Michelin S3 object storage or NFS/block storage as Nextcloud primary storage? Data layout, scaling, backup, migration and pitfalls from real operations. https://daniele-michelin.com/en/compare/nextcloud-vs-seafile/ https://daniele-michelin.com/assets/og/kb/en-v-nextcloud-vs-seafile.png Nextcloud vs Seafile: Comparison · Daniele Michelin Self-host Nextcloud or Seafile? Storage format, sync, features, updates and backup compared, plainly and from an operations point of view. https://daniele-michelin.com/en/compare/nginx-vs-apache-php-fpm/ https://daniele-michelin.com/assets/og/kb/en-v-nginx-vs-apache-php.png nginx vs Apache for PHP Apps · Daniele Michelin nginx or Apache in front of PHP-FPM? .htaccess, configuration, upload limits, timeouts and troubleshooting for Nextcloud, WordPress and other PHP apps. https://daniele-michelin.com/en/compare/saml-vs-oidc/ https://daniele-michelin.com/assets/og/kb/en-v-saml-vs-oidc.png SAML vs OIDC: Which One When? · Daniele Michelin SAML or OpenID Connect for single sign-on? Differences in protocol, clients, certificates and troubleshooting, from running Nextcloud with Keycloak. https://daniele-michelin.com/en/compare/spf-dkim-dmarc-differences/ https://daniele-michelin.com/assets/og/kb/en-v-spf-dkim-dmarc.png SPF vs DKIM vs DMARC: comparison table · Daniele Michelin What SPF, DKIM and DMARC each check, where they fail and why you need all three. Covers alignment, forwarding and common mistakes from practice. https://daniele-michelin.com/en/compare/systemd-timers-vs-cron/ https://daniele-michelin.com/assets/og/kb/en-v-systemd-timer-vs-cron.png systemd Timers vs Cron: Comparison · Daniele Michelin systemd timers or cron for scheduled jobs? Logging, missed runs, overlapping jobs, environment and effort compared, with everyday examples. https://daniele-michelin.com/en/data-oracle/ https://daniele-michelin.com/assets/og/data-oracle.jpg?v=1 The data oracle: just for fun with n8n and live data Pick a topic and the oracle reads your future from real live data: earthquakes, solar storms, the ISS and the moon. An n8n workflow with AI, for fun. https://daniele-michelin.com/en/demo/opscope/ https://daniele-michelin.com/assets/og/projects/opscope-demo-en.png OPSCOPE live demo: Linux server diagnostics · Daniele Michelin Recording of OPSCOPE, my read-only Bash toolkit for Linux servers: a simulated incident from diagnosis to report. https://daniele-michelin.com/en/email-ranking/banks/ https://daniele-michelin.com/assets/og/mail-ranking.png?v=1 E-mail ranking banks: who blocks phishing with DMARC? How well do 22 well-known domains protect their sender address from spoofing? SPF, DMARC and MTA-STS compared, graded A to F, sortable and free. https://daniele-michelin.com/en/errors/apt-could-not-get-lock-dpkg-lock-frontend/ https://daniele-michelin.com/assets/og/kb/en-e-apt-dpkg-lock.png apt: could not get lock dpkg lock-frontend · Daniele Michelin apt says Could not get lock /var/lib/dpkg/lock-frontend. Usually unattended-upgrades is running. How to wait, find the holder and recover safely. https://daniele-michelin.com/en/errors/apt-e-unable-to-locate-package/ https://daniele-michelin.com/assets/og/kb/en-e-apt-unable-to-locate-package.png apt: E: Unable to locate package · Daniele Michelin apt install fails with E: Unable to locate package. Stale package lists, a wrong name, a missing repository component or an end-of-life release. Checks and fixes. https://daniele-michelin.com/en/errors/apt-nopubkey-signature/ https://daniele-michelin.com/assets/og/kb/en-e-apt-nopubkey-signature.png apt: NO_PUBKEY – signature not verifiable · Daniele Michelin apt reports NO_PUBKEY when a repository signing key is missing or expired. Here is how to fetch the right key instead of ignoring warnings. https://daniele-michelin.com/en/errors/bash-argument-list-too-long/ https://daniele-michelin.com/assets/og/kb/en-e-bash-argument-list-too-long.png bash: Argument list too long (rm, cp, mv) · Daniele Michelin rm, cp or mv fail with Argument list too long. The shell expanded * to more files than the kernel allows. Use find with -delete or -exec, or xargs. Checks and fixes. https://daniele-michelin.com/en/errors/certbot-failed-to-renew-certificate-renewals-failed/ https://daniele-michelin.com/assets/og/kb/en-e-certbot-failed-to-renew-certificate.png certbot: failed to renew certificate · Daniele Michelin certbot renew prints Failed to renew certificate and the cert will expire. Changed authenticator, port 80 busy, missing timer or broken hook. Dry-run and fix. https://daniele-michelin.com/en/errors/certbot-timeout-during-connect-firewall/ https://daniele-michelin.com/assets/og/kb/en-e-certbot-timeout-during-connect.png Certbot: timeout during connect (firewall) · Daniele Michelin Let's Encrypt fails with Timeout during connect (likely firewall problem). Port 80 blocked, wrong IP or an unreachable IPv6 address. Checks and the fix. https://daniele-michelin.com/en/errors/change-dns-server/ https://daniele-michelin.com/assets/og/kb/en-e-dns-server-wechseln.png Change your DNS server on the router or PC · Daniele Michelin Pages will not load but ping 8.8.8.8 works? That points to DNS. Test with nslookup and switch the DNS server, with a note on privacy. https://daniele-michelin.com/en/errors/change-wifi-channel-2-4-vs-5-ghz/ https://daniele-michelin.com/assets/og/kb/en-e-wlan-kanal-wechseln.png Change Wi-Fi channel: choose 2.4 or 5 GHz · Daniele Michelin Which Wi-Fi band and channel fits? Explains 2.4 and 5 GHz, channels 1, 6, 11, checking neighbour networks with real commands and changing it in the router. https://daniele-michelin.com/en/errors/cron-job-not-running/ https://daniele-michelin.com/assets/og/kb/en-e-cron-job-laeuft-nicht.png Cron job not running: causes and checks · Daniele Michelin A cron job is listed but never runs, usually because of PATH, environment, permissions or a syntax error. Here is how to find it in minutes. https://daniele-michelin.com/en/errors/curl-6-could-not-resolve-host/ https://daniele-michelin.com/assets/og/kb/en-e-curl-6-could-not-resolve-host.png curl: (6) Could not resolve host · Daniele Michelin curl fails with (6) Could not resolve host. No DNS record yet, a typo, a resolver problem or a stale cache. Find out which with dig and getent. https://daniele-michelin.com/en/errors/dig-connection-timed-out-no-servers-could-be-reached/ https://daniele-michelin.com/assets/og/kb/en-e-dns-no-servers-could-be-reached.png dig: no servers could be reached (timed out) · Daniele Michelin dig or nslookup print connection timed out; no servers could be reached. The DNS server is down, unreachable or filtered on port 53. Find which hop fails and fix it. https://daniele-michelin.com/en/errors/dkim-fail-body-hash-did-not-verify/ https://daniele-michelin.com/assets/og/kb/en-e-dkim-body-hash-did-not-verify.png DKIM: body hash did not verify – fix · Daniele Michelin dkim=fail (body hash did not verify): the message body changed after signing. Find the footer, filter or gateway that modifies mail and sign last. https://daniele-michelin.com/en/errors/dmarc-unauthenticated-email-not-accepted-dmarc-policy/ https://daniele-michelin.com/assets/og/kb/en-e-dmarc-policy-rejected.png DMARC: rejected due to domain's DMARC policy · Daniele Michelin 550 5.7.1 Unauthenticated email is not accepted due to the domain's DMARC policy. Align SPF and DKIM for your sender, check forwarders and move p=reject safely. https://daniele-michelin.com/en/errors/dns-cname-at-zone-apex-not-allowed/ https://daniele-michelin.com/assets/og/kb/en-e-dns-cname-apex.png DNS: CNAME at zone apex not allowed – fix · Daniele Michelin Error “CNAME and other data” or “CNAME at apex not allowed”: the root domain cannot have a CNAME. Why that is, and which alternatives actually work. https://daniele-michelin.com/en/errors/dns-nxdomain-dns-probe-finished-nxdomain/ https://daniele-michelin.com/assets/og/kb/en-e-dns-nxdomain.png DNS NXDOMAIN / DNS_PROBE_FINISHED_NXDOMAIN fix · Daniele Michelin NXDOMAIN or DNS_PROBE_FINISHED_NXDOMAIN means DNS says the name does not exist. Find the typo, missing record, broken delegation or negative cache. https://daniele-michelin.com/en/errors/dns-servfail-dnssec/ https://daniele-michelin.com/assets/og/kb/en-e-dns-servfail.png DNS SERVFAIL: find the cause (DNSSEC & more) · Daniele Michelin dig returns SERVFAIL although the zone looks right? Often DNSSEC is broken, e.g. a stale DS record after a provider move. How to find and fix it. https://daniele-michelin.com/en/errors/dns-status-refused-query-refused/ https://daniele-michelin.com/assets/og/kb/en-e-dns-query-refused.png DNS: status REFUSED · Daniele Michelin dig shows status: REFUSED. A name server will not answer: the zone is not hosted there, recursion is not allowed for you, or an ACL blocks you. Checks and fixes. https://daniele-michelin.com/en/errors/docker-permission-denied-docker-sock/ https://daniele-michelin.com/assets/og/kb/en-e-docker-sock-permission-denied.png Docker: permission denied on docker.sock – fix · Daniele Michelin Docker says permission denied while trying to connect to the Docker daemon socket. Add your user to the docker group, re-login and know the security cost. https://daniele-michelin.com/en/errors/docker-port-already-allocated/ https://daniele-michelin.com/assets/og/kb/en-e-docker-port-already-allocated.png Docker: Bind failed – port already allocated · Daniele Michelin “port is already allocated” means another container or a host process holds the port. Here is how to find the owner and resolve it without rebooting. https://daniele-michelin.com/en/errors/dovecot-imap-login-disconnected-auth-failed/ https://daniele-michelin.com/assets/og/kb/en-e-dovecot-auth-failed.png Dovecot: Disconnected (auth failed) – fix · Daniele Michelin Dovecot logs “imap-login: Disconnected (auth failed)”? How to tell a wrong password from a config error or brute force, and how to fix the cause. https://daniele-michelin.com/en/errors/dovecot-mailbox-open-failed-permission-denied/ https://daniele-michelin.com/assets/og/kb/en-e-dovecot-mailbox-permission-denied.png Dovecot: permission denied on mailbox · Daniele Michelin Dovecot logs open() failed: Permission denied on a mailbox or Maildir. Wrong owner, wrong mail_location or uid settings after a migration. Checks and fixes. https://daniele-michelin.com/en/errors/dpkg-was-interrupted-configure-a/ https://daniele-michelin.com/assets/og/kb/en-e-dpkg-was-interrupted.png dpkg was interrupted: run dpkg --configure -a · Daniele Michelin apt stops with “dpkg was interrupted, you must manually run dpkg --configure -a”. An update was cut off or a package script failed. Checks and a safe repair order. https://daniele-michelin.com/en/errors/err-too-many-redirects-redirect-loop/ https://daniele-michelin.com/assets/og/kb/en-e-http-too-many-redirects.png ERR_TOO_MANY_REDIRECTS: redirected too many times · Daniele Michelin The browser shows ERR_TOO_MANY_REDIRECTS: redirected you too many times. A redirect loop between http and https, www, a CDN or the app. How to find and break it. https://daniele-michelin.com/en/errors/find-ip-address-gateway/ https://daniele-michelin.com/assets/og/kb/en-e-ip-adresse-gateway-finden.png Find your IP address and gateway (Win, Mac, Linux) · Daniele Michelin Router address unknown? Find your IP address and default gateway with ipconfig, ip route or route, and use it to open the router's settings page. https://daniele-michelin.com/en/errors/fritzbox-factory-reset/ https://daniele-michelin.com/assets/og/kb/en-e-fritzbox-werkseinstellungen.png Factory reset a FRITZ!Box: what will be lost? · Daniele Michelin Factory reset of a FRITZ!Box: when it makes sense, what you lose and how to save a backup of your settings first. Written for home users. https://daniele-michelin.com/en/errors/fritzbox-forgot-password/ https://daniele-michelin.com/assets/og/kb/en-e-fritzbox-passwort-vergessen.png FRITZ!Box password forgotten: how to get back in · Daniele Michelin Forgot your FRITZ!Box password? Find the default one on the device label, check that the box is reachable and get back into the settings. Plain steps. https://daniele-michelin.com/en/errors/fritzbox-no-internet/ https://daniele-michelin.com/assets/og/kb/en-e-fritzbox-internet-weg.png FRITZ!Box has no internet: 5 steps to check · Daniele Michelin No internet on your FRITZ!Box? Check lights, restart, cables and DNS in five steps, and learn when it makes sense to call your provider. https://daniele-michelin.com/en/errors/fritzbox-not-reachable/ https://daniele-michelin.com/assets/og/kb/en-e-fritzbox-nicht-erreichbar.png fritz.box won't open: causes and fix · Daniele Michelin fritz.box does not open? Check connection, the address 192.168.178.1, DNS and browser step by step with simple commands and find the cause. https://daniele-michelin.com/en/errors/fritzbox-wifi-password-find-change/ https://daniele-michelin.com/assets/og/kb/en-e-fritzbox-wlan-passwort.png Find or change the FRITZ!Box Wi-Fi password · Daniele Michelin Forgot your FRITZ!Box Wi-Fi password? Find it on the label, in the interface or on your computer, and change it safely. With menu hints for home users. https://daniele-michelin.com/en/errors/http-400-request-header-or-cookie-too-large/ https://daniele-michelin.com/assets/og/kb/en-e-http-400-header-too-large.png 400 Request Header Or Cookie Too Large: fix · Daniele Michelin nginx returns 400 “Request Header Or Cookie Too Large”: too many or too big cookies or tokens. Causes, a curl test and safe buffer sizes to set. https://daniele-michelin.com/en/errors/http-403-forbidden-nginx/ https://daniele-michelin.com/assets/og/kb/en-e-http-403.png HTTP 403 Forbidden in nginx: causes & fix · Daniele Michelin HTTP 403 Forbidden in nginx: missing index file, file permissions, deny rules or SELinux. How to find the exact cause in error.log and fix it fast. https://daniele-michelin.com/en/errors/http-404-not-found-nginx/ https://daniele-michelin.com/assets/og/kb/en-e-http-404-nginx.png nginx: 404 Not Found on pages that exist · Daniele Michelin nginx returns 404 Not Found although the page should exist. Wrong root or alias, missing try_files for the front controller, wrong server block. Checks and fixes. https://daniele-michelin.com/en/errors/http-413-request-entity-too-large/ https://daniele-michelin.com/assets/og/kb/en-e-http-413.png HTTP 413 Request Entity Too Large: nginx fix · Daniele Michelin 413 Request Entity Too Large: nginx or an upstream proxy blocks large uploads. How to set client_max_body_size and the PHP limits correctly. https://daniele-michelin.com/en/errors/http-429-too-many-requests/ https://daniele-michelin.com/assets/og/kb/en-e-http-429.png HTTP 429 Too Many Requests: causes and fix · Daniele Michelin HTTP 429 Too Many Requests means a rate limit was hit. Find which layer limits you (nginx limit_req, WAF, CDN, API) and raise, exempt or respect the limit correctly. https://daniele-michelin.com/en/errors/http-500-internal-server-error-php/ https://daniele-michelin.com/assets/og/kb/en-e-http-500.png HTTP 500 Internal Server Error: find the cause · Daniele Michelin HTTP 500 Internal Server Error is just the symptom. Find the real cause in nginx and PHP logs: fatal errors, memory limit, permissions, rewrite loops. https://daniele-michelin.com/en/errors/http-502-bad-gateway/ https://daniele-michelin.com/assets/og/kb/en-e-http-502.png HTTP 502 Bad Gateway (nginx, PHP-FPM): how to fix · Daniele Michelin 502 Bad Gateway in nginx: the backend (PHP-FPM, Node, Gunicorn) is not answering. Common causes, what to look for in error.log and quick fixes. https://daniele-michelin.com/en/errors/http-503-service-unavailable-nginx/ https://daniele-michelin.com/assets/og/kb/en-e-http-503.png HTTP 503 Service Unavailable: causes & fix · Daniele Michelin HTTP 503 Service Unavailable with nginx: rate limit, maintenance mode, overloaded backend or a load balancer without healthy servers. Find the source. https://daniele-michelin.com/en/errors/http-504-gateway-timeout/ https://daniele-michelin.com/assets/og/kb/en-e-http-504.png HTTP 504 Gateway Timeout (nginx): causes & fix · Daniele Michelin 504 Gateway Timeout in nginx: the backend takes longer than allowed. How to find slow scripts, a full PHP-FPM pool and wrong timeouts, and fix them. https://daniele-michelin.com/en/errors/http-521-522-origin-error-cdn/ https://daniele-michelin.com/assets/og/kb/en-e-http-521-522-origin.png HTTP 521 / 522: CDN cannot reach the origin · Daniele Michelin A CDN page shows 521 Web server is down or 522 Connection timed out. The edge cannot reach your origin: firewall, wrong IP, service down. Checks and fixes. https://daniele-michelin.com/en/errors/ https://daniele-michelin.com/assets/og/kb/en-hub-errors.png Error code lexicon for admins: SMTP, HTTP, Nextcloud Common error messages from mail, web servers, Nextcloud, DNS and SSO: what they mean, how to check them and how to fix them — with commands. https://daniele-michelin.com/en/errors/letsencrypt-acme-error-unauthorized/ https://daniele-michelin.com/assets/og/kb/en-e-acme-unauthorized.png Let's Encrypt acme:error:unauthorized: fix · Daniele Michelin certbot reports urn:ietf:params:acme:error:unauthorized? The HTTP-01 challenge fails, often due to an AAAA record or a redirect. Diagnosis and fix. https://daniele-michelin.com/en/errors/letsencrypt-too-many-certificates-already-issued/ https://daniele-michelin.com/assets/og/kb/en-e-letsencrypt-too-many-certificates.png Let's Encrypt too many certificates: rate limit · Daniele Michelin Let's Encrypt says “too many certificates already issued”? Which rate limit applies, how to wait it out safely and how to avoid issuance loops in future. https://daniele-michelin.com/en/errors/linux-no-space-left-on-device/ https://daniele-michelin.com/assets/og/kb/en-e-linux-no-space-left.png No space left on device despite free space · Daniele Michelin No space left on device but df shows free space? Usually inodes are exhausted or deleted files are still open. Diagnose with df -i and lsof +L1, then fix. https://daniele-michelin.com/en/errors/linux-out-of-memory-killed-process-oom-killer/ https://daniele-michelin.com/assets/og/kb/en-e-linux-oom-killer.png Linux OOM killer: out of memory, killed process · Daniele Michelin “Out of memory: Killed process” in the kernel log: the OOM killer ended a process. Find the culprit, limit memory per service and stop it happening again. https://daniele-michelin.com/en/errors/linux-read-only-file-system/ https://daniele-michelin.com/assets/og/kb/en-e-linux-read-only-file-system.png Linux: read-only file system – causes & fix · Daniele Michelin “Read-only file system” on Linux: filesystem errors with remount-ro, a failing disk, ro mount or systemd ProtectSystem. Diagnose it safely and fix it. https://daniele-michelin.com/en/errors/linux-too-many-open-files/ https://daniele-michelin.com/assets/og/kb/en-e-linux-too-many-open-files.png Linux: too many open files (EMFILE) – fix · Daniele Michelin “Too many open files” (error 24) in nginx, Java or Node: the per-process limit is reached. Check it properly, set LimitNOFILE in systemd, find leaks. https://daniele-michelin.com/en/errors/mariadb-table-is-marked-as-crashed-and-should-be-repaired/ https://daniele-michelin.com/assets/og/kb/en-e-mariadb-table-marked-as-crashed.png MariaDB: Table is marked as crashed · Daniele Michelin MariaDB or MySQL reports Table is marked as crashed and should be repaired (1194/145). Usually MyISAM or Aria after a crash. Back up first, then REPAIR TABLE. https://daniele-michelin.com/en/errors/mixed-content-blocked-insecure-resource/ https://daniele-michelin.com/assets/og/kb/en-e-http-mixed-content.png Mixed Content: blocked insecure resource · Daniele Michelin The browser console reports Mixed Content: the page was loaded over HTTPS but requested an insecure resource, and blocks it. Find the http:// URLs and fix them. https://daniele-michelin.com/en/errors/mount-wrong-fs-type-bad-option-bad-superblock/ https://daniele-michelin.com/assets/og/kb/en-e-mount-wrong-fs-type-bad-superblock.png mount: wrong fs type, bad option, bad superblock · Daniele Michelin mount fails with wrong fs type, bad option, bad superblock. Missing helper package, wrong type or option, no filesystem on the device or damage. Safe checks first. https://daniele-michelin.com/en/errors/mysql-1045-access-denied/ https://daniele-michelin.com/assets/og/kb/en-e-mysql-1045-access-denied.png MySQL error 1045: access denied for user · Daniele Michelin MySQL / MariaDB ERROR 1045 Access denied for user. Wrong password, wrong host or the root unix_socket plugin. Checks and the fix in minutes. https://daniele-michelin.com/en/errors/mysql-1064-syntax-error/ https://daniele-michelin.com/assets/og/kb/en-e-mysql-1064-syntax-error.png MariaDB/MySQL: ERROR 1064 syntax error · Daniele Michelin ERROR 1064 means the server cannot parse the statement. Usually a reserved word, a version difference or a broken quote – and the message shows where. https://daniele-michelin.com/en/errors/mysql-1067-invalid-default-value/ https://daniele-michelin.com/assets/og/kb/en-e-mysql-1067-invalid-default-value.png MySQL: ERROR 1067 Invalid default value · Daniele Michelin ERROR 1067 means a column default does not fit its type or the active sql_mode. Typical with TIMESTAMP, zero dates and old dumps. https://daniele-michelin.com/en/errors/mysql-2003-cant-connect-10061/ https://daniele-michelin.com/assets/og/kb/en-e-mysql-2003-cant-connect-10061.png MySQL: ERROR 2003 Can't connect (10061) · Daniele Michelin ERROR 2003 (HY000) with 10061 means nothing accepts connections on the target port. Usually the service is down, bound to localhost only, or filtered. https://daniele-michelin.com/en/errors/mysql-error-1040-too-many-connections/ https://daniele-michelin.com/assets/og/kb/en-e-mysql-1040-too-many-connections.png MySQL: ERROR 1040 Too many connections · Daniele Michelin MySQL or MariaDB refuses new clients with ERROR 1040 Too many connections. Find leaking apps and slow queries before raising max_connections. Checks and fixes. https://daniele-michelin.com/en/errors/mysql-error-2002-cant-connect-through-socket/ https://daniele-michelin.com/assets/og/kb/en-e-mysql-2002-socket.png MySQL error 2002: can't connect through socket · Daniele Michelin MySQL / MariaDB ERROR 2002: Can't connect to local server through socket. Server down, wrong socket path or full disk. Checks and fixes. https://daniele-michelin.com/en/errors/mysql-server-has-gone-away-2006/ https://daniele-michelin.com/assets/og/kb/en-e-mysql-2006-server-has-gone-away.png MySQL server has gone away (error 2006) · Daniele Michelin MySQL or MariaDB reports MySQL server has gone away, error 2006. An idle timeout, a packet above max_allowed_packet or a crashed server. Checks and fixes that last. https://daniele-michelin.com/en/errors/net-err-cert-authority-invalid-self-signed/ https://daniele-michelin.com/assets/og/kb/en-e-tls-cert-authority-invalid.png NET::ERR_CERT_AUTHORITY_INVALID: self-signed · Daniele Michelin Browser shows NET::ERR_CERT_AUTHORITY_INVALID: the certificate is self-signed, from an untrusted internal CA or served without its chain. How to check it and fix it. https://daniele-michelin.com/en/errors/net-err-cert-common-name-invalid/ https://daniele-michelin.com/assets/og/kb/en-e-tls-cert-common-name-invalid.png ERR_CERT_COMMON_NAME_INVALID: causes & fix · Daniele Michelin Chrome shows NET::ERR_CERT_COMMON_NAME_INVALID: the hostname is not in the certificate. Check the SAN, find the wrong vhost and expand the certificate. https://daniele-michelin.com/en/errors/net-err-cert-date-invalid-clock-wrong/ https://daniele-michelin.com/assets/og/kb/en-e-tls-cert-date-invalid.png NET::ERR_CERT_DATE_INVALID: clock or validity · Daniele Michelin NET::ERR_CERT_DATE_INVALID: the certificate is expired or not yet valid for the clock in use. Often the device clock is wrong. Compare the dates and fix it. https://daniele-michelin.com/en/errors/network-printer-not-found/ https://daniele-michelin.com/assets/og/kb/en-e-drucker-im-netzwerk-nicht-gefunden.png Printer not found on the network: causes and fix · Daniele Michelin Your Wi-Fi printer does not show up on your PC or phone? Common causes such as a different network or a new IP address, plus a step-by-step check. https://daniele-michelin.com/en/errors/nextcloud-cannot-write-into-config-directory/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-config-not-writable.png Nextcloud: cannot write into config directory · Daniele Michelin Nextcloud says Cannot write into config directory. Wrong owner after a restore, SELinux or config_is_read_only. Checks and the right permissions. https://daniele-michelin.com/en/errors/nextcloud-csrf-check-failed/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-csrf-check-failed.png Nextcloud “CSRF check failed”: causes & fix · Daniele Michelin Nextcloud says “CSRF check failed” on login or save? Usually the session is lost: check cookies, reverse proxy, session storage and Redis step by step. https://daniele-michelin.com/en/errors/nextcloud-data-directory-readable-by-other-users/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-data-dir-readable.png Nextcloud: data directory readable by other users · Daniele Michelin Nextcloud says “Your data directory is readable by other users”. How to set 0770 correctly, also on NFS and CIFS mounts, without breaking access. https://daniele-michelin.com/en/errors/nextcloud-database-is-missing-some-indexes/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-missing-indexes.png Nextcloud: database is missing some indexes – fix · Daniele Michelin Nextcloud says “The database is missing some indexes”. How to add missing indices, columns and primary keys safely with occ, even on large tables. https://daniele-michelin.com/en/errors/nextcloud-file-is-locked-423/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-423-locked.png Nextcloud "file is locked" (423 Locked): fix · Daniele Michelin Nextcloud says is locked or 423 Locked? Stale file locks after aborted requests. How to check Redis locking and cron, and clear old locks safely. https://daniele-michelin.com/en/errors/nextcloud-internal-server-error-request-id/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-internal-server-error.png Nextcloud Internal Server Error: find the cause · Daniele Michelin Nextcloud shows “Internal Server Error” with a request ID? How to find the matching entry in nextcloud.log and fix the most common causes directly. https://daniele-michelin.com/en/errors/nextcloud-last-background-job-ran-ago-cron/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-cron-last-job.png Nextcloud: last background job ran days ago – fix · Daniele Michelin Nextcloud says “Last background job execution ran … ago”? Check cron mode, the www-data crontab and errors in cron.php, then fix it permanently. https://daniele-michelin.com/en/errors/nextcloud-maintenance-mode-enabled/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-maintenance-mode.png Nextcloud stuck in maintenance mode: how to fix · Daniele Michelin Nextcloud stuck in maintenance mode, usually after an aborted update? How to check status with occ, finish the upgrade and turn maintenance off. https://daniele-michelin.com/en/errors/nextcloud-memcache-apcu-not-available-for-local-cache/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-memcache-apcu.png Nextcloud: memcache APCu not available – fix · Daniele Michelin Nextcloud shows “Memcache APCu not available for local cache” in occ or cron: usually apc.enable_cli=1 is missing in the CLI php.ini. Check and fix. https://daniele-michelin.com/en/errors/nextcloud-redisexception-redis-went-away/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-redis-went-away.png Nextcloud: RedisException: Redis went away · Daniele Michelin Nextcloud logs RedisException: Redis went away and pages hang or return 500. Redis is down, the socket or permissions are wrong, or memory ran out. Checks and fix. https://daniele-michelin.com/en/errors/nextcloud-reverse-proxy-header-configuration-incorrect/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-reverse-proxy-header.png Nextcloud: reverse proxy header incorrect – fix · Daniele Michelin Nextcloud warns the reverse proxy header configuration is incorrect. Set trusted_proxies and forwarded headers behind nginx, Traefik or Cloudflare. https://daniele-michelin.com/en/errors/nextcloud-saml-signature-validation-failed/ https://daniele-michelin.com/assets/og/kb/en-e-saml-signature-validation-failed.png SAML: signature validation failed in Nextcloud · Daniele Michelin Nextcloud user_saml says Signature validation failed. SAML Response rejected? Usually a rotated IdP certificate. Causes, checks and the fix. https://daniele-michelin.com/en/errors/nextcloud-some-files-have-not-passed-the-integrity-check/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-integrity-check-failed.png Nextcloud: some files failed the integrity check · Daniele Michelin Nextcloud lists INVALID_HASH, MISSING_FILE or EXTRA_FILE after the integrity check. Leftovers from a manual update or edited core files. How to read and fix it. https://daniele-michelin.com/en/errors/nextcloud-too-many-requests-brute-force-protection/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-too-many-requests.png Nextcloud: too many requests from your network · Daniele Michelin Nextcloud shows Too many requests from your network. Brute-force protection slows an IP. Reset it, whitelist an office, fix a shared proxy IP. https://daniele-michelin.com/en/errors/nextcloud-trusted-domain-error/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-trusted-domain.png Nextcloud "access through untrusted domain": fix · Daniele Michelin Nextcloud says access through untrusted domain: the hostname is missing from trusted_domains. How to add it with occ and check the reverse proxy. https://daniele-michelin.com/en/errors/nextcloud-updates-between-multiple-major-versions-unsupported/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-multiple-major-versions-unsupported.png Nextcloud: updates between major versions blocked · Daniele Michelin occ upgrade or the updater stops: updates between multiple major versions and downgrades are unsupported. Upgrade one major at a time or match code and database. https://daniele-michelin.com/en/errors/nextcloud-well-known-caldav-carddav-not-set-up/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-well-known-caldav-carddav.png Nextcloud: /.well-known/caldav not set up · Daniele Michelin Nextcloud warns that the web server cannot resolve /.well-known/caldav or carddav. Add the 301 redirects to /remote.php/dav in nginx or Apache. Checks and fix. https://daniele-michelin.com/en/errors/nextcloud-your-data-directory-is-invalid-ocdata/ https://daniele-michelin.com/assets/og/kb/en-e-nextcloud-data-directory-invalid.png Nextcloud: your data directory is invalid · Daniele Michelin Nextcloud says your data directory is invalid and asks for .ocdata. The volume is not mounted, the config.php path is wrong or the file is lost. Checks and fix. https://daniele-michelin.com/en/errors/nginx-bind-address-already-in-use/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-address-in-use.png nginx bind() failed (98): address already in use · Daniele Michelin nginx will not start: bind() to 0.0.0.0:80 failed (98: Address already in use). Find the process holding the port and fix it in a minute. https://daniele-michelin.com/en/errors/nginx-connect-failed-111-connection-refused-upstream/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-connection-refused-111.png nginx 111: Connection refused to upstream – fix · Daniele Michelin nginx logs “connect() failed (111: Connection refused) while connecting to upstream”: the backend is down or listens elsewhere. How to check and fix it. https://daniele-michelin.com/en/errors/nginx-could-not-build-server-names-hash/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-server-names-hash.png nginx: could not build server_names_hash · Daniele Michelin nginx -t fails with could not build server_names_hash, you should increase server_names_hash_bucket_size. Why it happens and the exact setting to change. https://daniele-michelin.com/en/errors/nginx-emerg-cannot-load-certificate-pem-no-start-line/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-cannot-load-certificate.png nginx: [emerg] cannot load certificate · Daniele Michelin nginx -t fails with cannot load certificate, no start line or key values mismatch. Wrong path, wrong file or a key that does not match. Checks and fixes. https://daniele-michelin.com/en/errors/nginx-php-fpm-primary-script-unknown-file-not-found/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-primary-script-unknown.png nginx PHP-FPM: Primary script unknown – fix · Daniele Michelin nginx shows “File not found.” and logs “Primary script unknown”: PHP-FPM cannot find the script. Check SCRIPT_FILENAME, root and container paths. https://daniele-michelin.com/en/errors/nginx-php-fpm-socket-13-permission-denied/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-fpm-socket-permission-denied.png nginx: PHP-FPM socket failed (13: Permission denied) nginx returns 502 and logs connect() to unix:/run/php/...sock failed (13: Permission denied). The nginx user may not use the PHP-FPM socket. Checks and the fix. https://daniele-michelin.com/en/errors/nginx-rewrite-or-internal-redirection-cycle/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-rewrite-redirection-cycle.png nginx: rewrite or internal redirection cycle · Daniele Michelin nginx logs rewrite or internal redirection cycle and answers 500. try_files points to a missing index.html or the root is wrong. Checks and fix. https://daniele-michelin.com/en/errors/nginx-upstream-prematurely-closed-connection/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-upstream-prematurely-closed.png nginx: upstream prematurely closed connection · Daniele Michelin nginx answers 502 and logs upstream prematurely closed connection while reading response header. The backend died, restarted or spoke the wrong protocol. https://daniele-michelin.com/en/errors/nginx-upstream-sent-too-big-header/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-too-big-header.png nginx: upstream sent too big header – fix · Daniele Michelin nginx logs upstream sent too big header and returns 502? The backend headers do not fit the buffer. How to raise the fastcgi and proxy buffers. https://daniele-michelin.com/en/errors/nginx-upstream-timed-out-110/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-upstream-timed-out.png nginx upstream timed out (110): causes and fix · Daniele Michelin nginx logs upstream timed out (110: Connection timed out) and users see 504. Find the slow backend, raise the right timeout and avoid the real cause. https://daniele-michelin.com/en/errors/nginx-worker-connections-are-not-enough/ https://daniele-michelin.com/assets/og/kb/en-e-nginx-worker-connections.png nginx: worker_connections are not enough · Daniele Michelin nginx logs worker_connections are not enough and requests fail or hang. The per-worker connection limit is reached. How to check the limits and raise them safely. https://daniele-michelin.com/en/errors/oidc-invalid-client-client-authentication-failed/ https://daniele-michelin.com/assets/og/kb/en-e-oidc-invalid-client.png OIDC: invalid_client at the token endpoint · Daniele Michelin OIDC login fails with invalid_client or Client authentication failed. Wrong or expired client secret, wrong auth method or unknown client ID. Checks and fixes. https://daniele-michelin.com/en/errors/oidc-invalid-grant-token-endpoint/ https://daniele-michelin.com/assets/og/kb/en-e-oidc-invalid-grant.png OIDC invalid_grant: causes & fix · Daniele Michelin OIDC error “invalid_grant” at the token endpoint: expired or reused code, mismatched redirect_uri, revoked refresh token or clock skew. How to fix it. https://daniele-michelin.com/en/errors/oidc-redirect-uri-mismatch-invalid-redirect-uri/ https://daniele-michelin.com/assets/og/kb/en-e-oidc-redirect-uri-mismatch.png OIDC redirect_uri_mismatch: causes & fix · Daniele Michelin OIDC error “redirect_uri_mismatch” or “Invalid parameter: redirect_uri”: the callback URL does not match the IdP registration. How to find the difference. https://daniele-michelin.com/en/errors/php-allowed-memory-size-exhausted/ https://daniele-michelin.com/assets/og/kb/en-e-php-memory-exhausted.png PHP: allowed memory size exhausted – how to fix · Daniele Michelin PHP Fatal error: Allowed memory size exhausted. Raise memory_limit in the right php.ini (FPM vs CLI), find the memory hog and stop it coming back. https://daniele-michelin.com/en/errors/php-call-to-undefined-function-mysqli-connect/ https://daniele-michelin.com/assets/og/kb/en-e-php-mysqli-undefined-function.png PHP: Call to undefined function mysqli_connect() · Daniele Michelin PHP stops with Call to undefined function mysqli_connect() (or Class mysqli not found). The mysqli extension is not loaded for the PHP version serving the site. https://daniele-michelin.com/en/errors/php-cannot-modify-header-information-headers-already-sent/ https://daniele-michelin.com/assets/og/kb/en-e-php-headers-already-sent.png PHP: Cannot modify header information · Daniele Michelin PHP warns Cannot modify header information - headers already sent by (output started at file:line). Output, a BOM or whitespace came before header(). https://daniele-michelin.com/en/errors/php-fpm-server-reached-pm-max-children/ https://daniele-michelin.com/assets/og/kb/en-e-php-fpm-max-children.png PHP-FPM: server reached pm.max_children · Daniele Michelin PHP-FPM logs server reached pm.max_children and the site slows down or returns 502/504. How to size the pool from your RAM and find slow requests. https://daniele-michelin.com/en/errors/php-maximum-execution-time-exceeded/ https://daniele-michelin.com/assets/og/kb/en-e-php-max-execution-time.png PHP: maximum execution time exceeded – fix · Daniele Michelin PHP Fatal error: Maximum execution time of 30 seconds exceeded. Raise max_execution_time safely, check the nginx timeout too, and fix the slow part. https://daniele-michelin.com/en/errors/php-parse-error-unexpected-token/ https://daniele-michelin.com/assets/og/kb/en-e-php-parse-error-unexpected-token.png PHP: Parse error unexpected token · Daniele Michelin PHP Parse error: unexpected token means the file is syntactically broken – often after a PHP upgrade, a cut-off upload or a missing semicolon. https://daniele-michelin.com/en/errors/php-uploaded-file-exceeds-upload-max-filesize/ https://daniele-michelin.com/assets/og/kb/en-e-php-upload-max-filesize.png PHP: uploaded file exceeds upload_max_filesize · Daniele Michelin Uploads fail with The uploaded file exceeds the upload_max_filesize directive in php.ini or POST Content-Length exceeds the limit. Which limits to raise and where. https://daniele-michelin.com/en/errors/port-forwarding-not-working/ https://daniele-michelin.com/assets/og/kb/en-e-portfreigabe-geht-nicht.png Port forwarding not working: causes and checks · Daniele Michelin Port forward set in the router but nothing reachable from outside? Often DS-Lite or CGNAT is to blame, otherwise firewall or a wrong address. Step-by-step checks. https://daniele-michelin.com/en/errors/postfix-deferred-connect-connection-timed-out/ https://daniele-michelin.com/assets/og/kb/en-e-postfix-connection-timed-out.png Postfix: connection timed out, mail deferred · Daniele Michelin Postfix status=deferred (connect to ...:25: Connection timed out). Outgoing port 25 blocked, firewall or IPv6 problem. Checks and fixes with a relay on 587. https://daniele-michelin.com/en/errors/postfix-host-or-domain-name-not-found-name-service-error/ https://daniele-michelin.com/assets/og/kb/en-e-postfix-host-not-found.png Postfix: host or domain name not found · Daniele Michelin Postfix status=deferred: Host or domain name not found, Name service error for type=MX. Check the resolver, the chroot and the recipient domain. https://daniele-michelin.com/en/errors/postfix-hostname-does-not-resolve-to-address/ https://daniele-michelin.com/assets/og/kb/en-e-postfix-hostname-does-not-resolve.png Postfix: hostname does not resolve to address · Daniele Michelin Postfix warning “hostname does not resolve to address”: the client's reverse and forward DNS do not match. When it is harmless and when you must act on it. https://daniele-michelin.com/en/errors/postfix-mail-for-domain-loops-back-to-myself/ https://daniele-michelin.com/assets/og/kb/en-e-postfix-mail-loops-back-to-myself.png Postfix: mail for domain loops back to myself · Daniele Michelin Postfix bounces with: mail for example.com loops back to myself. The MX or relay points at this server, but the domain is not set up locally. Find the loop and fix. https://daniele-michelin.com/en/errors/postfix-sasl-authentication-failed-no-mechanism-available/ https://daniele-michelin.com/assets/og/kb/en-e-postfix-sasl-authentication-failed.png Postfix: SASL authentication failed · Daniele Michelin Postfix cannot log in to the relay: SASL authentication failed, no mechanism available. Missing libsasl2 modules, sasl_passwd or TLS. Fixes. https://daniele-michelin.com/en/errors/postgres-too-many-clients/ https://daniele-michelin.com/assets/og/kb/en-e-postgres-too-many-clients.png Postgres: FATAL too many clients already · Daniele Michelin “sorry, too many clients already” means max_connections is exhausted. Usually open pools, a leak or idle transactions – here is how to measure it. https://daniele-michelin.com/en/errors/postgresql-fatal-no-pg-hba-conf-entry-for-host/ https://daniele-michelin.com/assets/og/kb/en-e-postgres-no-pg-hba-conf-entry.png PostgreSQL: no pg_hba.conf entry for host · Daniele Michelin PostgreSQL answers FATAL: no pg_hba.conf entry for host. No rule allows this client address, user, database or SSL mode. Check the rules and add a narrow line. https://daniele-michelin.com/en/errors/postgresql-fatal-password-authentication-failed/ https://daniele-michelin.com/assets/og/kb/en-e-postgres-password-authentication-failed.png PostgreSQL: password authentication failed · Daniele Michelin PostgreSQL rejects a login with FATAL: password authentication failed for user. Wrong password, another pg_hba.conf line or URL encoding. Checks and fixes. https://daniele-michelin.com/en/errors/reach-home-nas-from-outside/ https://daniele-michelin.com/assets/og/kb/en-e-nas-von-unterwegs-erreichen.png Reach your home NAS remotely: VPN vs port forward · Daniele Michelin How to reach a NAS or home PC from outside: VPN, port forwarding and DynDNS compared, with security notes and check commands. https://daniele-michelin.com/en/errors/redis-oom-command-not-allowed/ https://daniele-michelin.com/assets/og/kb/en-e-redis-oom-command-not-allowed.png Redis: OOM command not allowed · Daniele Michelin Redis reports “OOM command not allowed” when memory is above maxmemory and nothing may be evicted. Here is how to keep the cache writable. https://daniele-michelin.com/en/errors/restart-router-correctly/ https://daniele-michelin.com/assets/og/kb/en-e-router-neustart-richtig.png Restart your router the right way (and when) · Daniele Michelin Internet stuck or Wi-Fi acting up? Restart your router in the right order, use ping to confirm it helped, and learn when a restart will not fix the problem. https://daniele-michelin.com/en/errors/rsync-code-23-partial-transfer/ https://daniele-michelin.com/assets/og/kb/en-e-rsync-code-23-partial-transfer.png rsync: error code 23 (some files not transferred) · Daniele Michelin rsync exits with code 23 when individual files were not transferred: permissions, files changing during the run or attributes. The code alone says little. https://daniele-michelin.com/en/errors/saml-clock-skew-notbefore-timestamp-not-yet-valid/ https://daniele-michelin.com/assets/og/kb/en-e-saml-clock-skew.png SAML NotBefore / clock skew: fix timestamp errors · Daniele Michelin SAML error “Could not validate timestamp: not yet valid” or NotBefore/NotOnOrAfter: IdP and SP clocks differ. How to check it and fix it with NTP. https://daniele-michelin.com/en/errors/saml-invalid-audience-for-this-response/ https://daniele-michelin.com/assets/og/kb/en-e-saml-invalid-audience.png SAML: Invalid audience for this Response · Daniele Michelin SAML login fails with Invalid audience for this Response. The Entity ID in the IdP does not match the service provider's. Compare both values and fix the mismatch. https://daniele-michelin.com/en/errors/set-up-guest-wifi-network/ https://daniele-michelin.com/assets/og/kb/en-e-gastnetz-einrichten.png Set up a guest Wi-Fi network: guide and benefits · Daniele Michelin Why a guest network is useful, how to switch it on in your router and why printers, TVs and NAS are not visible there. With check commands. https://daniele-michelin.com/en/errors/smart-tv-chromecast-wont-connect/ https://daniele-michelin.com/assets/og/kb/en-e-smart-tv-chromecast-verbindet-nicht.png Smart TV or Chromecast won't connect: causes · Daniele Michelin Casting fails and the TV or Chromecast is missing in the app? Check same network, guest network, 2.4 GHz and router settings step by step. https://daniele-michelin.com/en/errors/smtp-421-4-7-0/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-421-470.png SMTP 421 4.7.0: rate limited – causes & fix · Daniele Michelin SMTP 421 4.7.0 means the receiver is temporarily throttling your IP. Common causes like missing PTR or a spam burst, how to diagnose and fix it. https://daniele-michelin.com/en/errors/smtp-450-4-1-8-sender-address-rejected-domain-not-found/ https://daniele-michelin.com/assets/og/kb/en-e-postfix-sender-domain-not-found.png SMTP: 450 4.1.8 Sender domain not found · Daniele Michelin Postfix rejects mail with 450 4.1.8 Sender address rejected: Domain not found. The sender domain has no A or MX record. Check DNS and fix the From address. https://daniele-michelin.com/en/errors/smtp-451-4-7-1-greylisting/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-451-471-greylisting.png SMTP 451 4.7.1 greylisting: causes & fix · Daniele Michelin SMTP 451 4.7.1 Greylisted is an intentional delay. When it is normal, when mail gets stuck and how to tune Postgrey or Rspamd greylisting. https://daniele-michelin.com/en/errors/smtp-530-5-7-0-must-issue-starttls/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-530-570-starttls.png SMTP 530 5.7.0: must issue STARTTLS first – fix · Daniele Michelin SMTP 530 5.7.0 means the server wants STARTTLS before it accepts login or mail. Causes, how to check with openssl and the right client settings. https://daniele-michelin.com/en/errors/smtp-535-5-7-8-authentication-failed/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-535-578.png SMTP 535 5.7.8: authentication failed – fix · Daniele Michelin SMTP 535 5.7.8 means the server rejected the SMTP login. Typical causes with Postfix/Dovecot, Gmail and Microsoft 365 and how to check each one. https://daniele-michelin.com/en/errors/smtp-550-5-1-1-user-unknown/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-550-511-user-unknown.png SMTP 550 5.1.1: user unknown – causes & fix · Daniele Michelin SMTP 550 5.1.1 means the recipient address does not exist on the target server. Check typos, missing mailbox maps and wrong domain class in Postfix. https://daniele-michelin.com/en/errors/smtp-550-5-4-1-recipient-address-rejected-access-denied/ https://daniele-michelin.com/assets/og/kb/en-e-exchange-online-550-541-access-denied.png SMTP: 550 5.4.1 Recipient address rejected · Daniele Michelin Microsoft 365 bounces with 550 5.4.1 Recipient address rejected: Access denied. The recipient is not in that tenant or the domain type is wrong. Checks and fixes. https://daniele-michelin.com/en/errors/smtp-550-5-7-1/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-550-571.png SMTP 550 5.7.1: Relay access denied – causes & fix · Daniele Michelin SMTP 550 5.7.1 means the mail server refuses to relay or rejects by policy. Common causes, how to check with postconf and how to fix it for good. https://daniele-michelin.com/en/errors/smtp-550-5-7-26/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-550-5726.png SMTP 550 5.7.26 / 5.7.23: Gmail DMARC & SPF fails · Daniele Michelin Gmail rejects with 550 5.7.26 or 5.7.23? SPF, DKIM or DMARC alignment is broken. How to check the DNS records and fix the bounce for good. https://daniele-michelin.com/en/errors/smtp-552-5-2-2-mailbox-full/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-552-522-mailbox-full.png SMTP 552 5.2.2: mailbox full (quota) – fix · Daniele Michelin SMTP 552 5.2.2 means the recipient's mailbox has reached its storage limit. How to check the Dovecot quota and free space for good, step by step. https://daniele-michelin.com/en/errors/smtp-553-5-7-1-sender-address-rejected/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-553-571-sender-rejected.png SMTP 553 5.7.1: sender address rejected – fix · Daniele Michelin SMTP 553 5.7.1 means the logged-in user may not send with this sender address. How to check smtpd_sender_login_maps and set up send-as properly. https://daniele-michelin.com/en/errors/smtp-554-5-7-1/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-554-571.png SMTP 554 5.7.1: blocklist rejection – how to fix · Daniele Michelin SMTP 554 5.7.1 with blocked using: your IP is on a blocklist like Spamhaus. Find the cause, stop the spam and request delisting the right way. https://daniele-michelin.com/en/errors/smtp-554-5-7-1-relay-access-denied/ https://daniele-michelin.com/assets/og/kb/en-e-postfix-relay-access-denied.png SMTP: 554 5.7.1 Relay access denied · Daniele Michelin Postfix answers 554 5.7.1 Relay access denied: sender not logged in, or the recipient domain is not handled here. Check the rules and fix without an open relay. https://daniele-michelin.com/en/errors/smtp-port-25-blocked/ https://daniele-michelin.com/assets/og/kb/en-e-smtp-port-25-gesperrt.png Port 25 blocked: mail delivery fails · Daniele Michelin Many providers and clouds block outbound port 25. Mail stays in the queue and timeouts pile up. Submission with auth or a relay is the way out. https://daniele-michelin.com/en/errors/speed-test-too-slow/ https://daniele-michelin.com/assets/og/kb/en-e-speedtest-zu-langsam.png Speed test shows less than your plan: causes · Daniele Michelin Speed test below the contract value? Contract and practice differ. Test by cable, check with ping and find the bottleneck in your Wi-Fi. https://daniele-michelin.com/en/errors/ssh-connect-to-host-port-22-connection-timed-out/ https://daniele-michelin.com/assets/og/kb/en-e-ssh-connection-timed-out.png SSH port 22: connection timed out – causes · Daniele Michelin ssh: connect to host port 22: Connection timed out. Firewall, wrong address, server down or fail2ban ban? How to tell and fix it, and timeout vs refused. https://daniele-michelin.com/en/errors/ssh-connection-refused-port-22/ https://daniele-michelin.com/assets/og/kb/en-e-ssh-connection-refused.png SSH: Connection refused on port 22 · Daniele Michelin SSH Connection refused means nothing accepts connections on that port. Usually the service is down, listens elsewhere, or the packet was rejected. https://daniele-michelin.com/en/errors/ssh-permission-denied-publickey/ https://daniele-michelin.com/assets/og/kb/en-e-ssh-permission-denied-publickey.png SSH: Permission denied (publickey) – fix · Daniele Michelin SSH says “Permission denied (publickey)”: wrong user, key missing from authorized_keys, wrong permissions or ssh-rsa disabled. Check it step by step. https://daniele-michelin.com/en/errors/ssh-remote-host-identification-has-changed/ https://daniele-michelin.com/assets/og/kb/en-e-ssh-host-key-changed.png SSH: remote host identification has changed · Daniele Michelin SSH warns REMOTE HOST IDENTIFICATION HAS CHANGED. Usually a reinstall or new server behind the same name. How to check the key and fix known_hosts safely. https://daniele-michelin.com/en/errors/ssh-too-many-authentication-failures/ https://daniele-michelin.com/assets/og/kb/en-e-ssh-too-many-authentication-failures.png SSH: too many authentication failures · Daniele Michelin SSH disconnects with Too many authentication failures before you type a password. The agent offers too many keys. Use IdentitiesOnly. https://daniele-michelin.com/en/errors/ssl-certificate-has-expired/ https://daniele-michelin.com/assets/og/kb/en-e-tls-certificate-expired.png SSL: certificate has expired – fix · Daniele Michelin “certificate has expired” or NET::ERR_CERT_DATE_INVALID: renewal failed, service not reloaded or wrong clock. How to check it and fix it for good. https://daniele-michelin.com/en/errors/ssl-error-rx-record-too-long/ https://daniele-michelin.com/assets/og/kb/en-e-tls-rx-record-too-long.png SSL_ERROR_RX_RECORD_TOO_LONG: causes & fix · Daniele Michelin Firefox shows SSL_ERROR_RX_RECORD_TOO_LONG: on port 443 the server answers with plain HTTP. Usually “ssl” is missing from the nginx listen line. https://daniele-michelin.com/en/errors/ssl-unable-to-get-local-issuer-certificate/ https://daniele-michelin.com/assets/og/kb/en-e-tls-unable-to-get-local-issuer.png unable to get local issuer certificate – fix · Daniele Michelin “SSL certificate problem: unable to get local issuer certificate” in curl, Python or Git: missing intermediates, CA bundle or TLS inspection. Fixes. https://daniele-michelin.com/en/errors/sudo-user-is-not-in-the-sudoers-file/ https://daniele-michelin.com/assets/og/kb/en-e-sudo-not-in-sudoers.png sudo: user is not in the sudoers file · Daniele Michelin sudo says “is not in the sudoers file. This incident will be reported.” The user lacks the sudo group or a rule. Check and fix it safely with usermod and visudo. https://daniele-michelin.com/en/errors/systemd-job-failed-control-process-exited-with-error-code/ https://daniele-michelin.com/assets/og/kb/en-e-systemd-job-failed-control-process.png systemd: job failed, control process exited · Daniele Michelin “Job for X.service failed because the control process exited with error code”: how to find the real error message with systemctl status and journalctl. https://daniele-michelin.com/en/errors/systemd-start-request-repeated-too-quickly/ https://daniele-michelin.com/assets/og/kb/en-e-systemd-start-limit-hit.png systemd: start request repeated too quickly · Daniele Michelin systemd: Start request repeated too quickly, Failed with result start-limit-hit. A crash loop hit the rate limit. Find the crash cause and reset the unit. https://daniele-michelin.com/en/errors/tar-unexpected-end-of-file/ https://daniele-michelin.com/assets/og/kb/en-e-tar-unexpected-end-of-file.png tar: unexpected end of file while extracting · Daniele Michelin “unexpected end of file” means the archive is incomplete – an interrupted download, a full disk or a stopped job. Here is how to salvage the rest. https://daniele-michelin.com/en/errors/temporary-failure-in-name-resolution/ https://daniele-michelin.com/assets/og/kb/en-e-linux-temporary-failure-name-resolution.png Temporary failure in name resolution · Daniele Michelin ping, apt or curl report Temporary failure in name resolution. The server cannot reach a DNS resolver: empty resolv.conf, resolved down or a blocked port 53. https://daniele-michelin.com/en/errors/tls-err-ssl-version-or-cipher-mismatch/ https://daniele-michelin.com/assets/og/kb/en-e-tls-version-cipher-mismatch.png ERR_SSL_VERSION_OR_CIPHER_MISMATCH – fix · Daniele Michelin ERR_SSL_VERSION_OR_CIPHER_MISMATCH: browser and server share no TLS version or cipher. Check ssl_protocols, ssl_ciphers and the virtual host certificate. https://daniele-michelin.com/en/errors/two-routers-double-nat/ https://daniele-michelin.com/assets/og/kb/en-e-mehrere-router-doppel-nat.png Two routers at home: double NAT explained · Daniele Michelin Two routers in a row cause double NAT, and port forwarding or game connections fail. How to spot the problem and fix it. https://daniele-michelin.com/en/errors/wifi-connected-no-internet/ https://daniele-michelin.com/assets/og/kb/en-e-wlan-verbunden-kein-internet.png Wi-Fi connected but no internet: how to check · Daniele Michelin Wi-Fi is up but websites do not load? Check step by step whether router, internet line or DNS is the cause, with real commands and simple fixes. https://daniele-michelin.com/en/errors/wifi-keeps-disconnecting/ https://daniele-michelin.com/assets/og/kb/en-e-wlan-bricht-ab.png Wi-Fi keeps disconnecting: dropouts and fixes · Daniele Michelin Wi-Fi drops again and again or cuts out briefly? Simple causes such as radio interference, power saving and router load, with a check using real commands. https://daniele-michelin.com/en/errors/wifi-repeater-or-mesh/ https://daniele-michelin.com/assets/og/kb/en-e-wlan-repeater-mesh.png Wi-Fi repeater or mesh: what suits your home · Daniele Michelin Dead spot at home: repeater or mesh? General comparison, correct placement, checking reception with real commands and when a cable is the best solution. https://daniele-michelin.com/en/errors/wifi-slow/ https://daniele-michelin.com/assets/og/kb/en-e-wlan-langsam.png Slow Wi-Fi: causes and checks at home · Daniele Michelin Wi-Fi connected but slow? Simple checks of distance, interference and router with real commands, plus typical fixes for a home network without special knowledge. https://daniele-michelin.com/en/glossary/a-aaaa-record/ https://daniele-michelin.com/assets/og/kb/en-g-a-aaaa.png What is an A record? AAAA and IPv6 explained · Daniele Michelin An A record maps a hostname to an IPv4 address, AAAA maps it to IPv6. How they work, how to check them with dig, and common dual-stack mistakes. https://daniele-michelin.com/en/glossary/acme/ https://daniele-michelin.com/assets/og/kb/en-g-acme.png What is ACME? Automated TLS certificates · Daniele Michelin ACME is the protocol Let's Encrypt and other CAs use to issue certificates automatically. HTTP-01, DNS-01, clients like certbot, and why renewals fail. https://daniele-michelin.com/en/glossary/authoritative-name-server/ https://daniele-michelin.com/assets/og/kb/en-g-authoritative.png What is an authoritative name server? · Daniele Michelin An authoritative name server holds the original data of a DNS zone and gives definitive answers. How it differs from a resolver and how to query it. https://daniele-michelin.com/en/glossary/bounce-ndr/ https://daniele-michelin.com/assets/og/kb/en-g-ndr.png What is a bounce (NDR)? Reading failure notices · Daniele Michelin A bounce or NDR says an email could not be delivered. How to read the status code, tell hard from soft bounces, and why backscatter is a problem. https://daniele-michelin.com/en/glossary/caa-record/ https://daniele-michelin.com/assets/og/kb/en-g-caa.png What is a CAA record? Restrict certificate issuers · Daniele Michelin A CAA record defines which certificate authorities may issue certificates for your domain. Syntax, an example, and the errors it causes with ACME. https://daniele-michelin.com/en/glossary/caldav-carddav/ https://daniele-michelin.com/assets/og/kb/en-g-caldav-carddav.png What are CalDAV and CardDAV? Sync explained · Daniele Michelin CalDAV syncs calendars and CardDAV syncs contacts, both built on WebDAV. Setup with Nextcloud, iOS, Android and Thunderbird, and the usual problems. https://daniele-michelin.com/en/glossary/certificate-chain/ https://daniele-michelin.com/assets/og/kb/en-g-cert-chain.png What is a certificate chain? Intermediates · Daniele Michelin The certificate chain links your server certificate through intermediates to a trusted root CA. Why serving the full chain matters and how to check it. https://daniele-michelin.com/en/glossary/cname-record/ https://daniele-michelin.com/assets/og/kb/en-g-cname.png What is a CNAME record? DNS aliases explained · Daniele Michelin A CNAME record makes one DNS name an alias of another. When to use it, why it is not allowed at the zone apex, and the mistakes that break it. https://daniele-michelin.com/en/glossary/content-security-policy/ https://daniele-michelin.com/assets/og/kb/en-g-csp.png What is a Content Security Policy (CSP)? · Daniele Michelin A Content Security Policy defines which sources a page may load scripts, styles and frames from. Directives, report-only mode, and the usual breakage. https://daniele-michelin.com/en/glossary/cron/ https://daniele-michelin.com/assets/og/kb/en-g-cron.png What is a cron job? Cron on Linux explained · Daniele Michelin Cron runs commands on a schedule on Linux. How a crontab line is built, how it compares to systemd timers, and why cron jobs fail without a trace. https://daniele-michelin.com/en/glossary/dkim/ https://daniele-michelin.com/assets/og/kb/en-g-dkim.png What is DKIM? Email signatures explained · Daniele Michelin DKIM signs outgoing email cryptographically and publishes the public key in DNS. How it works, what the selector is, and why dkim=fail happens. https://daniele-michelin.com/en/glossary/dmarc/ https://daniele-michelin.com/assets/og/kb/en-g-dmarc.png What is DMARC? Policy and reports explained · Daniele Michelin DMARC ties SPF and DKIM to the visible From address and tells receivers what to do with spoofed mail. Alignment, policy levels and aggregate reports. https://daniele-michelin.com/en/glossary/dns-propagation/ https://daniele-michelin.com/assets/og/kb/en-g-propagation.png What is DNS propagation? How long does it take? · Daniele Michelin DNS propagation is the time until all resolvers see a changed DNS answer. Why it depends on the TTL and not a fixed delay, and how to check it. https://daniele-michelin.com/en/glossary/dns-resolver/ https://daniele-michelin.com/assets/og/kb/en-g-resolver.png What is a DNS resolver? Recursion explained · Daniele Michelin A DNS resolver answers client queries by walking from the root to the right zone and caching the result. How recursion works and how to debug it. https://daniele-michelin.com/en/glossary/dnssec/ https://daniele-michelin.com/assets/og/kb/en-g-dnssec.png What is DNSSEC? Signed DNS answers explained · Daniele Michelin DNSSEC signs DNS records so resolvers can detect forged answers. How it works, what the DS record does, and why mistakes take your domain offline. https://daniele-michelin.com/en/glossary/escalation/ https://daniele-michelin.com/assets/og/kb/en-g-escalation.png What is an escalation in IT support? · Daniele Michelin An escalation hands a ticket to a higher support level or alerts management. Functional vs hierarchical escalation, and what a good handover contains. https://daniele-michelin.com/en/glossary/file-descriptor/ https://daniele-michelin.com/assets/og/kb/en-g-file-descriptor.png What is a file descriptor? Limits explained · Daniele Michelin A file descriptor is the number a process uses to refer to open files and sockets. Where Too many open files comes from and how to raise the limit. https://daniele-michelin.com/en/glossary/glue-record/ https://daniele-michelin.com/assets/og/kb/en-g-glue.png What is a glue record? DNS delegation explained · Daniele Michelin Glue records are name server IP addresses published in the parent zone. When you need them, how to set them, and what breaks when they are wrong. https://daniele-michelin.com/en/glossary/greylisting/ https://daniele-michelin.com/assets/og/kb/en-g-greylisting.png What is greylisting? Spam filtering by delay · Daniele Michelin Greylisting temporarily rejects mail from unknown senders and accepts it on the retry. How it works, its downsides, and how to spot it in your logs. https://daniele-michelin.com/en/glossary/hsts/ https://daniele-michelin.com/assets/og/kb/en-g-hsts.png What is HSTS? HTTP Strict Transport Security · Daniele Michelin HSTS tells browsers to reach a domain over HTTPS only. Header syntax, max-age, includeSubDomains, preload, and why rolling it back is hard. https://daniele-michelin.com/en/glossary/http-status-code/ https://daniele-michelin.com/assets/og/kb/en-g-http-status.png What is an HTTP status code? Classes explained · Daniele Michelin HTTP status codes show how a server answered a request. The five classes, key codes such as 301, 403 and 502, and how to read them when debugging. https://daniele-michelin.com/en/glossary/identity-provider/ https://daniele-michelin.com/assets/og/kb/en-g-idp.png What is an identity provider (IdP)? · Daniele Michelin An identity provider manages user accounts and confirms to applications, via SAML or OIDC, who is signed in. Examples, its role, and outage risks. https://daniele-michelin.com/en/glossary/imap/ https://daniele-michelin.com/assets/og/kb/en-g-imap.png What is IMAP? Mailbox access explained · Daniele Michelin IMAP is the protocol mail clients use to access a mailbox stored on the server. How it differs from POP3, ports 143 and 993, and common problems. https://daniele-michelin.com/en/glossary/ https://daniele-michelin.com/assets/og/kb/en-hub-glossary.png IT glossary for admins: DNS, mail, TLS, SSO · Daniele Michelin Terms from DNS, e-mail, TLS, single sign-on and Linux operations, explained briefly and practically — with examples and commands. https://daniele-michelin.com/en/glossary/inode/ https://daniele-michelin.com/assets/og/kb/en-g-inode.png What is an inode? Linux file systems explained · Daniele Michelin An inode stores a file's metadata in a Linux file system. Why a disk can be full while space is still free, and how to find what used up the inodes. https://daniele-michelin.com/en/glossary/journald/ https://daniele-michelin.com/assets/og/kb/en-g-journald.png What is journald? Reading logs with systemd · Daniele Michelin journald collects the logs of all services under systemd in a binary journal. Key journalctl commands, size limits and making logs persistent. https://daniele-michelin.com/en/glossary/json-web-token/ https://daniele-michelin.com/assets/og/kb/en-g-jwt.png What is a JWT? JSON Web Token explained · Daniele Michelin A JWT is a signed token made of header, payload and signature, used in OIDC and APIs. Structure, validation, expiry, and common security mistakes. https://daniele-michelin.com/en/glossary/logrotate/ https://daniele-michelin.com/assets/og/kb/en-g-logrotate.png What is logrotate? Rotating log files · Daniele Michelin logrotate rotates, compresses and deletes old log files automatically. How a config is built, copytruncate vs postrotate, and the usual mistakes. https://daniele-michelin.com/en/glossary/mta-mail-transfer-agent/ https://daniele-michelin.com/assets/og/kb/en-g-mta.png What is an MTA? Mail transfer agent explained · Daniele Michelin An MTA accepts email over SMTP and passes it to the next server, for example Postfix or Exim. How it differs from MUA and MDA and what the queue is for. https://daniele-michelin.com/en/glossary/mta-sts/ https://daniele-michelin.com/assets/og/kb/en-g-mta-sts.png What is MTA-STS? Enforcing TLS for inbound mail · Daniele Michelin MTA-STS forces sending mail servers to deliver over TLS with a valid certificate. The TXT record, the policy file, testing vs enforce, and pitfalls. https://daniele-michelin.com/en/glossary/multi-factor-authentication/ https://daniele-michelin.com/assets/og/kb/en-g-mfa.png What is MFA? Multi-factor authentication · Daniele Michelin MFA requires a second factor at login besides the password, such as an app code, push prompt or security key. Methods, weaknesses and support cases. https://daniele-michelin.com/en/glossary/mx-record/ https://daniele-michelin.com/assets/og/kb/en-g-mx.png What is an MX record? Mail routing in DNS · Daniele Michelin The MX record tells the world which server accepts email for a domain. Priorities, checking with dig, and the usual mistakes during a migration. https://daniele-michelin.com/en/glossary/nextcloud/ https://daniele-michelin.com/assets/og/kb/en-g-nextcloud.png What is Nextcloud? Architecture for admins · Daniele Michelin Nextcloud is a self-hosted platform for files, calendars, contacts and collaboration. Building blocks: PHP, database, cache, storage. https://daniele-michelin.com/en/glossary/ns-record/ https://daniele-michelin.com/assets/og/kb/en-g-ns.png What is an NS record? DNS delegation explained · Daniele Michelin NS records define which name servers are responsible for a zone. Delegation at the registry, checking with dig, and pitfalls when switching DNS host. https://daniele-michelin.com/en/glossary/nxdomain/ https://daniele-michelin.com/assets/og/kb/en-g-nxdomain.png What does NXDOMAIN mean? DNS error explained · Daniele Michelin NXDOMAIN means the queried name does not exist in DNS. How it differs from NODATA and SERVFAIL, typical causes, and how to diagnose it with dig. https://daniele-michelin.com/en/glossary/oauth-2-0/ https://daniele-michelin.com/assets/og/kb/en-g-oauth2.png What is OAuth 2.0? Authorization explained · Daniele Michelin OAuth 2.0 lets applications access resources without knowing the user's password. Roles, access and refresh tokens, and which flows to use today. https://daniele-michelin.com/en/glossary/oom-killer/ https://daniele-michelin.com/assets/og/kb/en-g-oom-killer.png What is the OOM killer? Linux memory explained · Daniele Michelin The OOM killer terminates processes on Linux when memory runs out. How it picks its victim, how to find it in the logs, and what actually fixes it. https://daniele-michelin.com/en/glossary/openid-connect/ https://daniele-michelin.com/assets/og/kb/en-g-oidc.png What is OpenID Connect (OIDC)? Explained · Daniele Michelin OpenID Connect adds login and identity on top of OAuth 2.0. ID token, discovery document, client ID and redirect URI, and the usual setup mistakes. https://daniele-michelin.com/en/glossary/php-fpm/ https://daniele-michelin.com/assets/og/kb/en-g-php-fpm.png What is PHP-FPM? Pools and tuning explained · Daniele Michelin PHP-FPM runs PHP code in its own process pool that nginx or Apache reach via FastCGI. Pool settings, pm.max_children, and the errors you will see. https://daniele-michelin.com/en/glossary/ptr-record/ https://daniele-michelin.com/assets/og/kb/en-g-ptr.png What is a PTR record? Reverse DNS explained · Daniele Michelin A PTR record resolves an IP address back to a hostname. Why mail servers need one, who controls it, and how to check reverse DNS with dig. https://daniele-michelin.com/en/glossary/relay-open-relay/ https://daniele-michelin.com/assets/og/kb/en-g-open-relay.png What is a mail relay? Open relays explained · Daniele Michelin A relay forwards email to domains it is not responsible for. When that is intended, why an open relay is dangerous, and what Relay access denied means. https://daniele-michelin.com/en/glossary/reverse-proxy/ https://daniele-michelin.com/assets/og/kb/en-g-reverse-proxy.png What is a reverse proxy? What it does · Daniele Michelin A reverse proxy accepts requests and forwards them to backend servers, for example nginx in front of Nextcloud. Its jobs, headers and common errors. https://daniele-michelin.com/en/glossary/root-cause-analysis/ https://daniele-michelin.com/assets/og/kb/en-g-rca.png What is a root cause analysis (RCA)? · Daniele Michelin A root cause analysis looks for the underlying cause of an incident, not just the symptom. The process, 5 Whys, and a useful report. https://daniele-michelin.com/en/glossary/rpo-rto/ https://daniele-michelin.com/assets/og/kb/en-g-rpo-rto.png What are RPO and RTO? Recovery objectives · Daniele Michelin RPO defines how much data loss is acceptable, RTO how fast a system must be back. Examples, how they drive backup design, and why restore tests matter. https://daniele-michelin.com/en/glossary/s3-object-storage/ https://daniele-michelin.com/assets/og/kb/en-g-s3.png What is S3 object storage? Buckets explained · Daniele Michelin S3 object storage keeps data as objects in buckets, accessed via an HTTP API. How it differs from a file system, using it with Nextcloud, and pitfalls. https://daniele-michelin.com/en/glossary/saml/ https://daniele-michelin.com/assets/og/kb/en-g-saml.png What is SAML? The SSO protocol explained · Daniele Michelin SAML 2.0 is an XML-based protocol for single sign-on between an identity provider and an application. The flow, metadata, certificates, common errors. https://daniele-michelin.com/en/glossary/scim/ https://daniele-michelin.com/assets/og/kb/en-g-scim.png What is SCIM? User provisioning explained · Daniele Michelin SCIM syncs users and groups automatically from the identity provider into applications. How it differs from SSO, how it works, and common pitfalls. https://daniele-michelin.com/en/glossary/server-name-indication/ https://daniele-michelin.com/assets/og/kb/en-g-sni.png What is SNI? Server Name Indication explained · Daniele Michelin SNI tells the server during the TLS handshake which hostname the client wants, so many HTTPS sites can share one IP. How it works and what breaks. https://daniele-michelin.com/en/glossary/service-level-agreement/ https://daniele-michelin.com/assets/og/kb/en-g-sla.png What is an SLA? Service level agreement · Daniele Michelin An SLA defines measurable targets such as response time, resolution time and availability. Key terms, what 99.9% really means, and common pitfalls. https://daniele-michelin.com/en/glossary/service-provider/ https://daniele-michelin.com/assets/og/kb/en-g-sp.png What is a service provider (SP) in SSO? · Daniele Michelin In SSO the service provider is the application that trusts the identity provider, for example Nextcloud with SAML. Entity ID, ACS URL, common errors. https://daniele-michelin.com/en/glossary/single-sign-on/ https://daniele-michelin.com/assets/og/kb/en-g-sso.png What is single sign-on (SSO)? Explained · Daniele Michelin With SSO, users sign in once at an identity provider and reach several applications. Protocols involved, operational benefits, and common pitfalls. https://daniele-michelin.com/en/glossary/smtp/ https://daniele-michelin.com/assets/og/kb/en-g-smtp.png What is SMTP? Email delivery explained · Daniele Michelin SMTP is the protocol mail servers use to deliver email to each other. How a session works, ports 25, 587 and 465, and how to read SMTP reply codes. https://daniele-michelin.com/en/glossary/snapshot-vs-backup/ https://daniele-michelin.com/assets/og/kb/en-g-snapshot-backup.png Snapshot vs backup: what is the difference? · Daniele Michelin A snapshot freezes the state of a volume, a backup is an independent copy stored elsewhere. Why snapshots alone are not a backup, and how to use both. https://daniele-michelin.com/en/glossary/soa-record/ https://daniele-michelin.com/assets/og/kb/en-g-soa.png What is a SOA record? Fields explained · Daniele Michelin The SOA record sits at the top of every DNS zone. What serial, refresh, retry, expire and minimum mean, and why the serial number matters. https://daniele-michelin.com/en/glossary/spf/ https://daniele-michelin.com/assets/og/kb/en-g-spf.png What is SPF? Sender Policy Framework explained · Daniele Michelin SPF uses a TXT record to define which servers may send mail for a domain. Syntax, the 10 DNS lookup limit, and the mistakes that break delivery. https://daniele-michelin.com/en/glossary/srv-record/ https://daniele-michelin.com/assets/og/kb/en-g-srv.png What is an SRV record? Service discovery in DNS · Daniele Michelin An SRV record publishes host and port of a service such as Autodiscover, CalDAV, SIP or XMPP. Field layout, an example and how to check with dig. https://daniele-michelin.com/en/glossary/starttls/ https://daniele-michelin.com/assets/og/kb/en-g-starttls.png What is STARTTLS? Upgrading to encryption · Daniele Michelin STARTTLS upgrades a plain-text SMTP, IMAP or POP3 connection to TLS. How it works, how it differs from implicit TLS, and its known weaknesses. https://daniele-michelin.com/en/glossary/subject-alternative-name/ https://daniele-michelin.com/assets/og/kb/en-g-san.png What is a SAN? Subject Alternative Name · Daniele Michelin The Subject Alternative Name lists every hostname a TLS certificate is valid for. Why the Common Name no longer counts and how to inspect the SANs. https://daniele-michelin.com/en/glossary/submission-port-587/ https://daniele-michelin.com/assets/og/kb/en-g-submission.png What is mail submission? Port 587 vs 25 and 465 · Daniele Michelin Submission is the SMTP service mail clients and apps use to send mail. How port 587 differs from 25 and 465, and why authentication is mandatory. https://daniele-michelin.com/en/glossary/support-levels-1st-2nd-3rd/ https://daniele-michelin.com/assets/og/kb/en-g-support-levels.png 1st, 2nd, 3rd level support: differences · Daniele Michelin Support levels split requests by complexity: intake and standard cases, technical analysis, engineering and vendor. What each level does, handovers. https://daniele-michelin.com/en/glossary/systemd-unit/ https://daniele-michelin.com/assets/og/kb/en-g-systemd-unit.png What is a systemd unit? Unit files explained · Daniele Michelin A systemd unit describes a service, timer or mount managed by systemd. How unit files are structured, how to override them, and how to find start errors. https://daniele-michelin.com/en/glossary/tls/ https://daniele-michelin.com/assets/og/kb/en-g-tls.png What is TLS? Transport Layer Security explained · Daniele Michelin TLS encrypts connections such as HTTPS, IMAPS and SMTP and proves the server's identity with a certificate. The handshake, versions and common errors. https://daniele-michelin.com/en/glossary/ttl/ https://daniele-michelin.com/assets/og/kb/en-g-ttl.png What is TTL in DNS? Time to live explained · Daniele Michelin TTL sets how long resolvers may cache a DNS record. Sensible values, how to lower TTL before a migration, and the most common misunderstandings. https://daniele-michelin.com/en/glossary/txt-record/ https://daniele-michelin.com/assets/og/kb/en-g-txt.png What is a TXT record? Uses and limits · Daniele Michelin TXT records hold free text in DNS and carry SPF, DKIM, DMARC and domain verification tokens. Format, the 255-character limit and common errors. https://daniele-michelin.com/en/glossary/webdav/ https://daniele-michelin.com/assets/og/kb/en-g-webdav.png What is WebDAV? File access over HTTP · Daniele Michelin WebDAV extends HTTP with methods to read, write and manage files on a server. How Nextcloud uses it, which clients support it, and common errors. https://daniele-michelin.com/en/header-ranking/banks/ https://daniele-michelin.com/assets/og/header-ranking.png?v=1 Header ranking banks: security headers of 19 banks · Daniele Michelin How well do 19 banks and payment providers set their security headers? Heatmap graded A to F, sortable, with a live check on every row. https://daniele-michelin.com/en/link-galaxy/ https://daniele-michelin.com/assets/og/link-galaxy.png?v=1 Link galaxy: your website as a 3D star map Enter a domain: an n8n workflow crawls the site and shows it as a 3D galaxy. Broken links, orphan pages and deep pages at a glance. https://daniele-michelin.com/en/n8n-live/ https://daniele-michelin.com/assets/og/n8n-live.png?v=1 n8n live: start a real workflow with one click One click starts an n8n workflow: ISS, earthquakes, Hacker News, Wikipedia, weather and more, and an AI writes a bulletin. Watch it live. https://daniele-michelin.com/en/orbit-postcard/ https://daniele-michelin.com/assets/og/orbit-postcard.png?v=1 Orbit postcard: a live greeting from the ISS via n8n Press the button and the ISS sends you a postcard with a real NASA satellite image of the spot it is flying over right now. Built with n8n and AI. https://daniele-michelin.com/en/ports/110/ https://daniele-michelin.com/assets/og/kb/en-p-110.png Port 110: POP3 with STARTTLS · Daniele Michelin Port 110 for POP3: fetching mail with STARTTLS, why port 995 with implicit TLS is preferred, and when you can close port 110 entirely. https://daniele-michelin.com/en/ports/11211/ https://daniele-michelin.com/assets/og/kb/en-p-11211.png Port 11211: Memcached, local only · Daniele Michelin Port 11211 for Memcached: the cache behind many PHP apps. Why UDP 11211 was abused for record DDoS attacks and how to lock Memcached down. https://daniele-michelin.com/en/ports/1194/ https://daniele-michelin.com/assets/og/kb/en-p-1194.png Port 1194: OpenVPN over UDP · Daniele Michelin Port 1194 for OpenVPN: UDP by default, TCP or port 443 as a fallback. Firewall rules, MTU problems and how OpenVPN compares to WireGuard. https://daniele-michelin.com/en/ports/123/ https://daniele-michelin.com/assets/og/kb/en-p-123.png Port 123: NTP time synchronization · Daniele Michelin Port 123/UDP for NTP: why accurate time matters for TLS, Kerberos and 2FA, whether the port must be open, and how to verify sync on Linux. https://daniele-michelin.com/en/ports/143/ https://daniele-michelin.com/assets/og/kb/en-p-143.png Port 143: IMAP with STARTTLS · Daniele Michelin Port 143 for IMAP: mailbox access with STARTTLS, how it differs from port 993, and why you should prevent plaintext logins on port 143. https://daniele-michelin.com/en/ports/20-21/ https://daniele-michelin.com/assets/og/kb/en-p-20-21.png Port 20/21: FTP and its firewall pitfalls · Daniele Michelin Port 21 is the FTP control channel, port 20 the active-mode data channel. Why FTP needs a passive port range and when SFTP is the better choice. https://daniele-michelin.com/en/ports/2049/ https://daniele-michelin.com/assets/og/kb/en-p-2049.png Port 2049: NFS shares on the LAN · Daniele Michelin Port 2049 for NFS: NFSv4 needs only this port, NFSv3 also needs rpcbind and mountd. Firewall rules, permission issues and security basics. https://daniele-michelin.com/en/ports/22/ https://daniele-michelin.com/assets/og/kb/en-p-22.png Port 22: securing SSH and SFTP · Daniele Michelin Port 22 for SSH and SFTP: what runs there, how to harden access with keys, Fail2ban and IP allowlists, and how to fix common login errors. https://daniele-michelin.com/en/ports/25/ https://daniele-michelin.com/assets/og/kb/en-p-25.png Port 25: SMTP between mail servers · Daniele Michelin Port 25 is for mail transport between servers (MX), not for mail clients. Why providers block outbound port 25 and how to test STARTTLS on it. https://daniele-michelin.com/en/ports/3306/ https://daniele-michelin.com/assets/og/kb/en-p-3306.png Port 3306: MySQL and MariaDB · Daniele Michelin Port 3306 for MySQL and MariaDB: why the database should never be public, bind-address, SSH tunnels and the most common connection errors. https://daniele-michelin.com/en/ports/3389/ https://daniele-michelin.com/assets/og/kb/en-p-3389.png Port 3389: running RDP safely · Daniele Michelin Port 3389 for Remote Desktop (RDP): why it should never face the internet directly, NLA, VPN or RD Gateway, and common connection errors. https://daniele-michelin.com/en/ports/3478/ https://daniele-michelin.com/assets/og/kb/en-p-3478.png Port 3478: STUN/TURN for Nextcloud Talk · Daniele Michelin Port 3478 for STUN/TURN with coturn: how Nextcloud Talk calls work behind NAT. Firewall rules, relay ports, external-ip and common errors. https://daniele-michelin.com/en/ports/389/ https://daniele-michelin.com/assets/og/kb/en-p-389.png Port 389: LDAP and StartTLS · Daniele Michelin Port 389 for LDAP and Active Directory: directory access with StartTLS, why the port never belongs on the internet, and typical bind errors. https://daniele-michelin.com/en/ports/4190/ https://daniele-michelin.com/assets/og/kb/en-p-4190.png Port 4190: ManageSieve for mail filters · Daniele Michelin Port 4190 for ManageSieve: manage server-side mail filters and vacation replies with Sieve from Roundcube, Thunderbird and Nextcloud Mail. https://daniele-michelin.com/en/ports/443/ https://daniele-michelin.com/assets/og/kb/en-p-443.png Port 443: HTTPS, TLS and HTTP/3 · Daniele Michelin Port 443 for HTTPS: TCP for TLS, UDP for HTTP/3 (QUIC). How to check the certificate chain and SNI and fix common TLS errors on web servers. https://daniele-michelin.com/en/ports/465/ https://daniele-michelin.com/assets/og/kb/en-p-465.png Port 465: SMTPS with implicit TLS · Daniele Michelin Port 465 for sending mail with implicit TLS, the recommended option again since RFC 8314. How it differs from port 587 and common client mistakes. https://daniele-michelin.com/en/ports/51820/ https://daniele-michelin.com/assets/og/kb/en-p-51820.png Port 51820: WireGuard VPN · Daniele Michelin Port 51820/UDP for WireGuard: the usual ListenPort, why port scans show nothing, and how to fix handshake, NAT and MTU problems on tunnels. https://daniele-michelin.com/en/ports/53/ https://daniele-michelin.com/assets/og/kb/en-p-53.png Port 53: DNS over UDP and TCP · Daniele Michelin Port 53 for DNS: why TCP must be open alongside UDP, when the port may be public, and how open resolvers get abused for amplification attacks. https://daniele-michelin.com/en/ports/5432/ https://daniele-michelin.com/assets/og/kb/en-p-5432.png Port 5432: securing PostgreSQL · Daniele Michelin Port 5432 for PostgreSQL: listen_addresses, pg_hba.conf and why the database should never be public. How to fix the most common connection errors. https://daniele-michelin.com/en/ports/587/ https://daniele-michelin.com/assets/og/kb/en-p-587.png Port 587: SMTP submission with STARTTLS · Daniele Michelin Port 587 for sending mail from clients: submission with STARTTLS and mandatory login. Port 587 or 465? Differences and the most common errors. https://daniele-michelin.com/en/ports/636/ https://daniele-michelin.com/assets/og/kb/en-p-636.png Port 636: LDAPS with implicit TLS · Daniele Michelin Port 636 for LDAPS: LDAP over implicit TLS for Nextcloud, mail and Active Directory. Fixing certificate problems and restricting access. https://daniele-michelin.com/en/ports/6379/ https://daniele-michelin.com/assets/og/kb/en-p-6379.png Port 6379: never expose Redis · Daniele Michelin Port 6379 for Redis: why open Redis instances get hijacked, protected-mode, passwords, Unix sockets, and using Redis as a cache for Nextcloud. https://daniele-michelin.com/en/ports/80/ https://daniele-michelin.com/assets/og/kb/en-p-80.png Port 80: HTTP, redirects and ACME · Daniele Michelin Port 80 for HTTP: why it should stay open even with HTTPS, how Let's Encrypt HTTP-01 uses it, and which redirect mistakes are most common. https://daniele-michelin.com/en/ports/8080/ https://daniele-michelin.com/assets/og/kb/en-p-8080.png Port 8080: alternate HTTP port · Daniele Michelin Port 8080 as the alternate HTTP port for proxies, Tomcat, Docker containers and backends. Why it shouldn't be public, plus the Docker firewall trap. https://daniele-michelin.com/en/ports/8443/ https://daniele-michelin.com/assets/og/kb/en-p-8443.png Port 8443: alternate HTTPS and Plesk · Daniele Michelin Port 8443 as the alternate HTTPS port: Plesk panel, Tomcat, UniFi and admin interfaces. How to restrict access and fix certificate errors. https://daniele-michelin.com/en/ports/853/ https://daniele-michelin.com/assets/og/kb/en-p-853.png Port 853: DNS over TLS (DoT) · Daniele Michelin Port 853 for DNS over TLS and DNS over QUIC: encrypted DNS queries, Android Private DNS, firewall rules and how it compares to DNS over HTTPS. https://daniele-michelin.com/en/ports/9000/ https://daniele-michelin.com/assets/og/kb/en-p-9000.png Port 9000: PHP-FPM and FastCGI · Daniele Michelin Port 9000 for PHP-FPM: FastCGI between nginx and PHP, why an exposed port 9000 allows code execution, and how to fix 502 Bad Gateway errors. https://daniele-michelin.com/en/ports/9090/ https://daniele-michelin.com/assets/og/kb/en-p-9090.png Port 9090: Prometheus server and Cockpit · Daniele Michelin Port 9090 for the Prometheus server: web UI and API with no built-in login. Cockpit also uses port 9090. How to secure it and troubleshoot targets. https://daniele-michelin.com/en/ports/9100/ https://daniele-michelin.com/assets/og/kb/en-p-9100.png Port 9100: Prometheus node_exporter · Daniele Michelin Port 9100 for the Prometheus node_exporter: system metrics for monitoring. Why the port should only be reachable from your Prometheus server. https://daniele-michelin.com/en/ports/993/ https://daniele-michelin.com/assets/og/kb/en-p-993.png Port 993: IMAPS with implicit TLS · Daniele Michelin Port 993 for IMAPS: mailbox access with implicit TLS, the recommended setting for mail clients. Fixing certificate and login problems. https://daniele-michelin.com/en/ports/995/ https://daniele-michelin.com/assets/og/kb/en-p-995.png Port 995: POP3S with implicit TLS · Daniele Michelin Port 995 for POP3S: downloading mail over implicit TLS. When POP3 still makes sense, how to secure the port, and why messages disappear. https://daniele-michelin.com/en/ports/ https://daniele-michelin.com/assets/og/kb/en-hub-ports.png Network ports for admins: list with explanations · Daniele Michelin The key TCP/UDP ports for mail, web, DNS, databases and VPN: what runs there, whether it should be open and how to check it. https://daniele-michelin.com/en/projects/acestudio-mac/ https://daniele-michelin.com/assets/og/projects/acestudio-mac-en.png ACE Studio – Native macOS app for local AI music ACE Studio is a SwiftUI front-end for a local ACE-Step 1.5 install: you describe a song, the app writes lyrics and style, drives the engine and keeps the… https://daniele-michelin.com/en/projects/ai-receptionist/ https://daniele-michelin.com/assets/og/projects/ai-receptionist-en.png Local AI Receptionist – AI phone receptionist, fully local An AI receptionist that answers the phone (a Twilio number) or replies in the browser, books appointments and speaks Italian (with a Milanese accent) and… https://daniele-michelin.com/en/projects/famiglia-os/ https://daniele-michelin.com/assets/og/projects/famiglia-os-en.png FamigliaOS – The digital home, self-hosted · Daniele Michelin FamigliaOS aims to bring calendar, tasks, meal planning and more for the whole family into one place – as a self-hosted app in a single container. https://daniele-michelin.com/en/projects/jarvis/ https://daniele-michelin.com/assets/og/projects/jarvis-en.png J.A.R.V.I.S. – AI assistant for macOS with 120+ tools J.A.R.V.I.S. is a cyberpunk-styled AI assistant for macOS: a Python/FastAPI backend and a Vite/TypeScript frontend, with text, voice and vision input. All… https://daniele-michelin.com/en/projects/job-hunter/ https://daniele-michelin.com/assets/og/projects/job-hunter-en.png job-hunter – Self-hosted job search assistant job-hunter finds new postings every morning, scores them against your own profile and writes a short German cover letter with AI. https://daniele-michelin.com/en/projects/llm-wiki/ https://daniele-michelin.com/assets/og/projects/llm-wiki-en.png LLM-Wiki – RAG over your own documents · Daniele Michelin LLM-Wiki is a RAG system for your own documents: ask questions by text or voice and get answers backed by the sources they came from. https://daniele-michelin.com/en/projects/zimage-turbo-pipeline/ https://daniele-michelin.com/assets/og/projects/zimage-turbo-pipeline-en.png zimage-turbo-pipeline – automatic AI video pipeline The pipeline fetches current news, has Gemini write image prompts and copy, generates images, music and a voice-over, and assembles a vertical video with… https://daniele-michelin.com/en/report-card/ https://daniele-michelin.com/assets/og/report-card.png?v=1 Website report card: what grade does your site get? Enter a domain and get a school report card for your website: grades for security headers, e-mail protection and the TLS certificate, with teacher remarks. https://daniele-michelin.com/en/website-city/ https://daniele-michelin.com/assets/og/website-city.png?v=2 Your website as a city: live with n8n and AI Enter a domain and see your website as a 3D model town: town hall as homepage, sections as districts, security headers as watchtowers. https://daniele-michelin.com/en/website-dna/ https://daniele-michelin.com/assets/og/website-dna.png?v=1 Website DNA: which foreign genes does your site load? Enter a domain: an n8n workflow sequences your homepage. Own code, third parties, libraries with CVEs, cookies, shown as a 3D double helix. https://daniele-michelin.com/fehler/apt-could-not-get-lock-dpkg-lock-frontend/ https://daniele-michelin.com/assets/og/kb/de-e-apt-dpkg-lock.png apt: Could not get lock – dpkg lock-frontend · Daniele Michelin apt meldet Could not get lock /var/lib/dpkg/lock-frontend. Meist läuft unattended-upgrades. So wartest du und stellst den Zustand sicher wieder her. https://daniele-michelin.com/fehler/apt-e-unable-to-locate-package/ https://daniele-michelin.com/assets/og/kb/de-e-apt-unable-to-locate-package.png apt: Unable to locate package – Lösung · Daniele Michelin apt install bricht mit E: Unable to locate package ab. Veraltete Paketlisten, falscher Paketname, fehlende Komponente oder ein beendetes Release. Prüfung und Lösung. https://daniele-michelin.com/fehler/apt-nopubkey-signatur/ https://daniele-michelin.com/assets/og/kb/de-e-apt-nopubkey-signature.png apt: NO_PUBKEY – Signatur nicht prüfbar · Daniele Michelin apt meldet NO_PUBKEY, wenn der Signaturschlüssel eines Repos fehlt oder abgelaufen ist. So holst du den richtigen Key, statt Warnungen zu ignorieren. https://daniele-michelin.com/fehler/bash-argument-list-too-long/ https://daniele-michelin.com/assets/og/kb/de-e-bash-argument-list-too-long.png bash: Argument list too long (rm, cp, mv) – Lösung · Daniele Michelin rm, cp oder mv brechen mit Argument list too long ab. Die Shell hat * zu mehr Dateien erweitert, als der Kernel erlaubt. Lösung mit find und xargs. https://daniele-michelin.com/fehler/certbot-failed-to-renew-certificate-renewals-failed/ https://daniele-michelin.com/assets/og/kb/de-e-certbot-failed-to-renew-certificate.png certbot: Zertifikat konnte nicht erneuert werden · Daniele Michelin certbot renew meldet Failed to renew certificate, das Zertifikat läuft ab. Authenticator geändert, Port 80 belegt, Timer fehlt oder Hook defekt. Dry-Run und Lösung. https://daniele-michelin.com/fehler/certbot-timeout-during-connect-firewall/ https://daniele-michelin.com/assets/og/kb/de-e-certbot-timeout-during-connect.png Certbot: Timeout during connect – Firewall prüfen · Daniele Michelin Let's Encrypt scheitert mit Timeout during connect. Port 80 gesperrt, falsche IP oder nicht erreichbares IPv6. Prüfung und Lösung. https://daniele-michelin.com/fehler/cronjob-laeuft-nicht/ https://daniele-michelin.com/assets/og/kb/de-e-cron-job-laeuft-nicht.png Cronjob läuft nicht: Ursachen und Prüfung · Daniele Michelin Ein Cronjob läuft nicht, obwohl er in der crontab steht: meist PATH, Umgebung, Rechte oder ein Syntaxfehler. So findest du es in wenigen Minuten. https://daniele-michelin.com/fehler/curl-6-could-not-resolve-host/ https://daniele-michelin.com/assets/og/kb/de-e-curl-6-could-not-resolve-host.png curl: (6) Could not resolve host – Lösung · Daniele Michelin curl scheitert mit (6) Could not resolve host. Noch kein DNS-Eintrag, Tippfehler, Resolver-Problem oder alter Cache. Mit dig und getent klären. https://daniele-michelin.com/fehler/dig-connection-timed-out-no-servers-could-be-reached/ https://daniele-michelin.com/assets/og/kb/de-e-dns-no-servers-could-be-reached.png dig: no servers could be reached (Timeout) · Daniele Michelin dig oder nslookup melden connection timed out; no servers could be reached. DNS-Server down, unerreichbar oder Port 53 gefiltert. Den Fehlerort finden und beheben. https://daniele-michelin.com/fehler/dkim-fail-body-hash-did-not-verify/ https://daniele-michelin.com/assets/og/kb/de-e-dkim-body-hash-did-not-verify.png DKIM: Body Hash did not verify – Ursachen · Daniele Michelin dkim=fail (body hash did not verify): Der Text wurde nach dem Signieren verändert. Footer, Filter oder Gateway finden und zuletzt signieren. https://daniele-michelin.com/fehler/dmarc-unauthenticated-email-not-accepted-dmarc-policy/ https://daniele-michelin.com/assets/og/kb/de-e-dmarc-policy-rejected.png DMARC: E-Mail wegen DMARC-Richtlinie abgelehnt · Daniele Michelin 550 5.7.1 Unauthenticated email is not accepted due to the domain's DMARC policy. SPF und DKIM ausrichten, Weiterleitungen prüfen, p=reject sicher einführen. https://daniele-michelin.com/fehler/dns-cname-at-zone-apex-not-allowed/ https://daniele-michelin.com/assets/og/kb/de-e-dns-cname-apex.png DNS: CNAME an der Zonen-Apex nicht erlaubt · Daniele Michelin Fehler „CNAME and other data“ oder „CNAME at apex not allowed“: Die Hauptdomain darf keinen CNAME haben. Warum, und welche Alternativen funktionieren. https://daniele-michelin.com/fehler/dns-nxdomain-dns-probe-finished-nxdomain/ https://daniele-michelin.com/assets/og/kb/de-e-dns-nxdomain.png DNS NXDOMAIN / DNS_PROBE_FINISHED_NXDOMAIN · Daniele Michelin NXDOMAIN bzw. DNS_PROBE_FINISHED_NXDOMAIN heißt: Der Name existiert laut DNS nicht. Tippfehler, fehlender Record, Delegation oder Negativ-Cache finden. https://daniele-michelin.com/fehler/dns-server-wechseln/ https://daniele-michelin.com/assets/og/kb/de-e-dns-server-wechseln.png DNS-Server wechseln im Router oder am PC · Daniele Michelin Seiten laden nicht, aber ping 8.8.8.8 geht? Das spricht für ein DNS-Problem. So testen Sie mit nslookup und wechseln den DNS-Server, mit Hinweis zum Datenschutz. https://daniele-michelin.com/fehler/dns-servfail-dnssec/ https://daniele-michelin.com/assets/og/kb/de-e-dns-servfail.png DNS SERVFAIL: Ursachen finden (DNSSEC & Co.) · Daniele Michelin dig liefert SERVFAIL, obwohl die Zone stimmt? Häufig ist DNSSEC kaputt, etwa ein alter DS-Record nach Providerwechsel. So finden und beheben Sie es. https://daniele-michelin.com/fehler/dns-status-refused-query-refused/ https://daniele-michelin.com/assets/og/kb/de-e-dns-query-refused.png DNS: status REFUSED – Ursachen und Lösung · Daniele Michelin dig zeigt status: REFUSED. Ein Nameserver antwortet nicht: Zone nicht vorhanden, Rekursion nicht erlaubt oder eine ACL sperrt dich. Prüfung und Lösung. https://daniele-michelin.com/fehler/docker-permission-denied-docker-sock/ https://daniele-michelin.com/assets/og/kb/de-e-docker-sock-permission-denied.png Docker: permission denied bei docker.sock · Daniele Michelin Docker meldet permission denied beim Verbinden mit dem Daemon-Socket. Benutzer zur Gruppe docker hinzufügen, neu anmelden und das Risiko kennen. https://daniele-michelin.com/fehler/docker-port-already-allocated/ https://daniele-michelin.com/assets/og/kb/de-e-docker-port-already-allocated.png Docker: port is already allocated · Daniele Michelin „port is already allocated“ heißt: Ein anderer Container oder ein Host-Prozess belegt den Port. So findest du den Besitzer und löst den Konflikt. https://daniele-michelin.com/fehler/dovecot-imap-login-disconnected-auth-failed/ https://daniele-michelin.com/assets/og/kb/de-e-dovecot-auth-failed.png Dovecot: Disconnected (auth failed) beheben · Daniele Michelin Dovecot meldet „imap-login: Disconnected (auth failed)“? So trennen Sie falsches Passwort, Konfigurationsfehler und Brute-Force. https://daniele-michelin.com/fehler/dovecot-mailbox-open-failed-permission-denied/ https://daniele-michelin.com/assets/og/kb/de-e-dovecot-mailbox-permission-denied.png Dovecot: Permission denied im Postfach – Lösung · Daniele Michelin Dovecot meldet open() failed: Permission denied bei Postfach oder Maildir. Falscher Besitzer oder mail_location nach Migration. Prüfung und Lösung. https://daniele-michelin.com/fehler/dpkg-was-interrupted-configure-a/ https://daniele-michelin.com/assets/og/kb/de-e-dpkg-was-interrupted.png dpkg was interrupted: configure -a – Lösung · Daniele Michelin apt stoppt mit „dpkg was interrupted, you must manually run dpkg --configure -a“. Ein Update brach ab oder ein Skript scheiterte. Prüfung und sichere Reparatur. https://daniele-michelin.com/fehler/drucker-im-netzwerk-nicht-gefunden/ https://daniele-michelin.com/assets/og/kb/de-e-drucker-im-netzwerk-nicht-gefunden.png Drucker im Netzwerk nicht gefunden: Ursachen · Daniele Michelin Der WLAN-Drucker taucht am PC oder Handy nicht auf? Typische Ursachen wie anderes Netz oder neue IP-Adresse und eine Schritt-für-Schritt-Prüfung. https://daniele-michelin.com/fehler/err-too-many-redirects-redirect-loop/ https://daniele-michelin.com/assets/og/kb/de-e-http-too-many-redirects.png ERR_TOO_MANY_REDIRECTS: zu viele Weiterleitungen · Daniele Michelin Der Browser zeigt ERR_TOO_MANY_REDIRECTS: hat Sie zu oft weitergeleitet. Weiterleitungsschleife zwischen http und https, www, CDN oder App. Finden und beheben. https://daniele-michelin.com/fehler/fritzbox-kein-internet/ https://daniele-michelin.com/assets/og/kb/de-e-fritzbox-internet-weg.png FRITZ!Box: Kein Internet – Prüfung in 5 Schritten · Daniele Michelin Kein Internet an der FRITZ!Box? Prüfen Sie Anzeigen, Neustart, Kabel und DNS in fünf Schritten und erfahren Sie, wann der Anruf beim Provider sinnvoll ist. https://daniele-michelin.com/fehler/fritzbox-nicht-erreichbar/ https://daniele-michelin.com/assets/og/kb/de-e-fritzbox-nicht-erreichbar.png fritz.box lässt sich nicht öffnen: Ursachen & Lösung fritz.box öffnet sich nicht? Prüfen Sie Verbindung, Adresse 192.168.178.1, DNS und Browser Schritt für Schritt mit einfachen Befehlen und finden Sie die Ursache. https://daniele-michelin.com/fehler/fritzbox-passwort-vergessen/ https://daniele-michelin.com/assets/og/kb/de-e-fritzbox-passwort-vergessen.png FRITZ!Box Passwort vergessen: Zugang zurückholen · Daniele Michelin FRITZ!Box-Kennwort vergessen? So finden Sie das Passwort auf dem Gerät, prüfen die Erreichbarkeit und kommen wieder in die Oberfläche. Einfach erklärt. https://daniele-michelin.com/fehler/fritzbox-werkseinstellungen/ https://daniele-michelin.com/assets/og/kb/de-e-fritzbox-werkseinstellungen.png FRITZ!Box zurücksetzen: Was geht verloren? · Daniele Michelin FRITZ!Box auf Werkseinstellungen zurücksetzen: wann es sinnvoll ist, was dabei verloren geht und wie Sie vorher eine Sicherung der Einstellungen anlegen. https://daniele-michelin.com/fehler/fritzbox-wlan-passwort-finden-aendern/ https://daniele-michelin.com/assets/og/kb/de-e-fritzbox-wlan-passwort.png FRITZ!Box WLAN-Passwort finden oder ändern · Daniele Michelin WLAN-Passwort der FRITZ!Box vergessen? So finden Sie es auf dem Aufkleber, in der Oberfläche oder am Rechner und ändern es sicher. Mit Menühinweisen. https://daniele-michelin.com/fehler/gastnetz-einrichten-anleitung/ https://daniele-michelin.com/assets/og/kb/de-e-gastnetz-einrichten.png Gastnetz einrichten: Anleitung und Nutzen · Daniele Michelin Wozu ein Gast-WLAN gut ist, wie Sie es im Router aktivieren und warum Drucker, Fernseher und NAS dort nicht sichtbar sind. Mit Prüfbefehlen. https://daniele-michelin.com/fehler/http-400-request-header-or-cookie-too-large/ https://daniele-michelin.com/assets/og/kb/de-e-http-400-header-too-large.png 400 Request Header Or Cookie Too Large beheben · Daniele Michelin nginx meldet 400 „Request Header Or Cookie Too Large“: zu viele oder zu große Cookies oder Tokens. Ursachen, Test mit curl und sichere Puffergrößen. https://daniele-michelin.com/fehler/http-403-forbidden-nginx/ https://daniele-michelin.com/assets/og/kb/de-e-http-403.png HTTP 403 Forbidden bei nginx: Ursache & Lösung · Daniele Michelin HTTP 403 Forbidden bei nginx: fehlende Index-Datei, Dateirechte, deny-Regeln oder SELinux. So finden Sie die Ursache im error.log und beheben sie. https://daniele-michelin.com/fehler/http-404-not-found-nginx/ https://daniele-michelin.com/assets/og/kb/de-e-http-404-nginx.png nginx: 404 Not Found bei vorhandenen Seiten · Daniele Michelin nginx liefert 404 Not Found, obwohl die Seite existieren sollte. Falsches root oder alias, fehlendes try_files, falscher Server-Block. Prüfung und Lösung. https://daniele-michelin.com/fehler/http-413-request-entity-too-large/ https://daniele-michelin.com/assets/og/kb/de-e-http-413.png HTTP 413 Request Entity Too Large: nginx-Fix · Daniele Michelin 413 Request Entity Too Large: nginx oder ein vorgeschalteter Proxy blockt große Uploads. So setzen Sie client_max_body_size und PHP-Limits richtig. https://daniele-michelin.com/fehler/http-429-too-many-requests/ https://daniele-michelin.com/assets/og/kb/de-e-http-429.png HTTP 429 Too Many Requests: Ursache und Lösung · Daniele Michelin HTTP 429 Too Many Requests heißt: Ein Rate-Limit greift. Finde die begrenzende Ebene (nginx, WAF, CDN, API) und passe das Limit richtig an oder beachte es. https://daniele-michelin.com/fehler/http-500-internal-server-error-php/ https://daniele-michelin.com/assets/og/kb/de-e-http-500.png HTTP 500 Internal Server Error: Ursache finden · Daniele Michelin HTTP 500 Internal Server Error ist nur das Symptom. Die echte Ursache steht im nginx- und PHP-Log: Fatal Error, Speicherlimit, Rechte, Rewrite-Schleife. https://daniele-michelin.com/fehler/http-502-bad-gateway/ https://daniele-michelin.com/assets/og/kb/de-e-http-502.png HTTP 502 Bad Gateway (nginx, PHP-FPM): Lösung · Daniele Michelin 502 Bad Gateway bei nginx: Das Backend (PHP-FPM, Node, Gunicorn) antwortet nicht. Ursachen, Prüfung im error.log und schnelle Lösungen. https://daniele-michelin.com/fehler/http-503-service-unavailable-nginx/ https://daniele-michelin.com/assets/og/kb/de-e-http-503.png HTTP 503 Service Unavailable: Ursachen & Lösung · Daniele Michelin HTTP 503 Service Unavailable bei nginx: Rate-Limit, Wartungsmodus, überlastetes Backend oder Load Balancer ohne gesunde Server finden. https://daniele-michelin.com/fehler/http-504-gateway-timeout/ https://daniele-michelin.com/assets/og/kb/de-e-http-504.png HTTP 504 Gateway Timeout (nginx): Ursachen & Lösung · Daniele Michelin 504 Gateway Timeout bei nginx: Das Backend braucht länger als erlaubt. Wie Sie langsame Skripte, volle PHP-FPM-Pools und Timeouts finden und beheben. https://daniele-michelin.com/fehler/http-521-522-origin-error-cdn/ https://daniele-michelin.com/assets/og/kb/de-e-http-521-522-origin.png HTTP 521 / 522: CDN erreicht den Origin nicht · Daniele Michelin Eine CDN-Seite zeigt 521 Web server is down oder 522 Connection timed out. Der Edge erreicht deinen Origin nicht: Firewall, falsche IP, Dienst aus. Lösung. https://daniele-michelin.com/fehler/ https://daniele-michelin.com/assets/og/kb/de-hub-errors.png Fehlercode-Lexikon für Admins: SMTP, HTTP, Nextcloud Häufige Fehlermeldungen aus Mail, Webserver, Nextcloud, DNS und SSO: was sie bedeuten, wie man sie prüft und behebt — mit Befehlen. https://daniele-michelin.com/fehler/ip-adresse-gateway-finden/ https://daniele-michelin.com/assets/og/kb/de-e-ip-adresse-gateway-finden.png IP-Adresse und Gateway finden (Windows, Mac, Linux) · Daniele Michelin Router-Adresse unbekannt? So finden Sie Ihre IP-Adresse und das Standardgateway mit ipconfig, ip route oder netstat, und öffnen damit das Router-Menü. https://daniele-michelin.com/fehler/letsencrypt-acme-error-unauthorized/ https://daniele-michelin.com/assets/og/kb/de-e-acme-unauthorized.png Let's Encrypt: acme:error:unauthorized beheben · Daniele Michelin certbot meldet urn:ietf:params:acme:error:unauthorized? Die HTTP-01-Challenge scheitert, oft wegen AAAA-Record oder Weiterleitung. Diagnose und Lösung. https://daniele-michelin.com/fehler/letsencrypt-too-many-certificates-already-issued/ https://daniele-michelin.com/assets/og/kb/de-e-letsencrypt-too-many-certificates.png Let's Encrypt: too many certificates – Rate Limit · Daniele Michelin Let's Encrypt meldet „too many certificates already issued“? Welches Rate Limit greift, wie Sie die Sperre abwarten und künftige Schleifen vermeiden. https://daniele-michelin.com/fehler/linux-no-space-left-on-device/ https://daniele-michelin.com/assets/og/kb/de-e-linux-no-space-left.png No space left on device trotz freiem Speicher · Daniele Michelin „No space left on device“, aber df zeigt freien Platz? Meist sind Inodes voll oder gelöschte Dateien noch offen. Diagnose mit df -i, lsof +L1 und Lösung. https://daniele-michelin.com/fehler/linux-out-of-memory-killed-process-oom-killer/ https://daniele-michelin.com/assets/og/kb/de-e-linux-oom-killer.png Linux OOM Killer: Out of memory – Killed process · Daniele Michelin „Out of memory: Killed process“ im Kernel-Log: Der OOM Killer hat einen Prozess beendet. Verursacher finden, Speicher begrenzen und Wiederholung vermeiden. https://daniele-michelin.com/fehler/linux-read-only-file-system/ https://daniele-michelin.com/assets/og/kb/de-e-linux-read-only-file-system.png Linux: Read-only file system – Ursache & Lösung · Daniele Michelin „Read-only file system“ unter Linux: Dateisystemfehler mit remount-ro, defekte Platte, ro-Mount oder systemd-ProtectSystem. Sicher diagnostizieren. https://daniele-michelin.com/fehler/linux-too-many-open-files/ https://daniele-michelin.com/assets/og/kb/de-e-linux-too-many-open-files.png Linux: Too many open files (EMFILE) beheben · Daniele Michelin „Too many open files“ (Fehler 24) bei nginx, Java oder Node: Limit pro Prozess erreicht. Richtig prüfen, LimitNOFILE in systemd setzen und Lecks finden. https://daniele-michelin.com/fehler/mariadb-table-is-marked-as-crashed-and-should-be-repaired/ https://daniele-michelin.com/assets/og/kb/de-e-mariadb-table-marked-as-crashed.png MariaDB: Table is marked as crashed – Lösung · Daniele Michelin MariaDB oder MySQL meldet Table is marked as crashed and should be repaired (1194/145). Meist MyISAM oder Aria nach einem Absturz. Erst sichern, dann REPAIR TABLE. https://daniele-michelin.com/fehler/mixed-content-blocked-insecure-resource/ https://daniele-michelin.com/assets/og/kb/de-e-http-mixed-content.png Mixed Content: unsichere Ressource blockiert · Daniele Michelin Die Browser-Konsole meldet Mixed Content: Seite per HTTPS geladen, aber unsichere Ressource angefordert, und blockiert sie. Die http://-URLs finden und beheben. https://daniele-michelin.com/fehler/mount-wrong-fs-type-bad-option-bad-superblock/ https://daniele-michelin.com/assets/og/kb/de-e-mount-wrong-fs-type-bad-superblock.png mount: wrong fs type, bad superblock – Lösung · Daniele Michelin mount scheitert mit wrong fs type, bad option, bad superblock. Fehlendes Hilfspaket, falscher Typ, kein Dateisystem oder Schaden. Erst sicher prüfen, dann handeln. https://daniele-michelin.com/fehler/mysql-1045-access-denied/ https://daniele-michelin.com/assets/og/kb/de-e-mysql-1045-access-denied.png MySQL 1045: Access denied for user – Lösung · Daniele Michelin MySQL / MariaDB ERROR 1045 Access denied for user. Falsches Passwort, falscher Host oder das unix_socket-Plugin bei root. Prüfungen und Lösung in Minuten. https://daniele-michelin.com/fehler/mysql-1064-syntax-error/ https://daniele-michelin.com/assets/og/kb/de-e-mysql-1064-syntax-error.png MariaDB/MySQL: ERROR 1064 Syntaxfehler · Daniele Michelin ERROR 1064 heißt: Der Server kann den Befehl nicht parsen. Meist sind es reservierte Wörter, Versionsunterschiede oder ein kaputtes Anführungszeichen. https://daniele-michelin.com/fehler/mysql-1067-invalid-default-value/ https://daniele-michelin.com/assets/og/kb/de-e-mysql-1067-invalid-default-value.png MySQL: ERROR 1067 Invalid default value · Daniele Michelin ERROR 1067 heißt: Der Default-Wert passt nicht zum Spaltentyp oder zum sql_mode. Typisch bei TIMESTAMP, Null-Datum und alten Dumps. https://daniele-michelin.com/fehler/mysql-2003-cant-connect-10061/ https://daniele-michelin.com/assets/og/kb/de-e-mysql-2003-cant-connect-10061.png MySQL: ERROR 2003 Can't connect (10061) · Daniele Michelin ERROR 2003 (HY000) mit 10061 heißt: Auf dem Zielport nimmt niemand Verbindungen an. Meist läuft der Dienst nicht, lauscht nur lokal oder eine Firewall blockt. https://daniele-michelin.com/fehler/mysql-error-1040-too-many-connections/ https://daniele-michelin.com/assets/og/kb/de-e-mysql-1040-too-many-connections.png MySQL: ERROR 1040 Too many connections – Lösung · Daniele Michelin MySQL oder MariaDB lehnt neue Clients mit ERROR 1040 Too many connections ab. Erst undichte Apps und langsame Abfragen finden, dann max_connections anheben. https://daniele-michelin.com/fehler/mysql-error-2002-cant-connect-through-socket/ https://daniele-michelin.com/assets/og/kb/de-e-mysql-2002-socket.png MySQL-Fehler 2002: Verbindung über Socket scheitert · Daniele Michelin MySQL / MariaDB ERROR 2002: Can't connect to local server through socket. Server aus, falscher Socket-Pfad oder volle Platte. Prüfungen und Lösungen. https://daniele-michelin.com/fehler/mysql-server-has-gone-away-2006/ https://daniele-michelin.com/assets/og/kb/de-e-mysql-2006-server-has-gone-away.png MySQL server has gone away (Fehler 2006) · Daniele Michelin MySQL oder MariaDB meldet MySQL server has gone away, Fehler 2006. Leerlauf-Timeout, Paket über max_allowed_packet oder abgestürzter Server. Prüfung und Lösung. https://daniele-michelin.com/fehler/nas-von-unterwegs-erreichen/ https://daniele-michelin.com/assets/og/kb/de-e-nas-von-unterwegs-erreichen.png NAS von unterwegs erreichen: VPN statt Portfreigabe · Daniele Michelin So erreichen Sie NAS oder Heim-PC von außen: VPN, Portfreigabe und DynDNS im Vergleich, mit Sicherheitshinweisen und Prüfbefehlen. https://daniele-michelin.com/fehler/net-err-cert-authority-invalid-self-signed/ https://daniele-michelin.com/assets/og/kb/de-e-tls-cert-authority-invalid.png ERR_CERT_AUTHORITY_INVALID: selbstsigniert · Daniele Michelin Browser zeigt NET::ERR_CERT_AUTHORITY_INVALID: Zertifikat selbstsigniert, von einer unbekannten internen CA oder ohne Kette ausgeliefert. Prüfung und Lösung. https://daniele-michelin.com/fehler/net-err-cert-common-name-invalid/ https://daniele-michelin.com/assets/og/kb/de-e-tls-cert-common-name-invalid.png ERR_CERT_COMMON_NAME_INVALID: Ursache & Lösung · Daniele Michelin Chrome meldet NET::ERR_CERT_COMMON_NAME_INVALID: Der aufgerufene Hostname steht nicht im Zertifikat. SAN prüfen, vHost finden, Zertifikat erweitern. https://daniele-michelin.com/fehler/net-err-cert-date-invalid-clock-wrong/ https://daniele-michelin.com/assets/og/kb/de-e-tls-cert-date-invalid.png ERR_CERT_DATE_INVALID: Uhrzeit oder Gültigkeit · Daniele Michelin NET::ERR_CERT_DATE_INVALID: Zertifikat abgelaufen oder für die genutzte Uhr noch nicht gültig. Oft ist die Geräteuhr falsch. Daten vergleichen und beheben. https://daniele-michelin.com/fehler/nextcloud-cannot-write-into-config-directory/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-config-not-writable.png Nextcloud: In „config“ kann nicht geschrieben werden Nextcloud meldet Cannot write into config directory. Falscher Besitzer nach Restore, SELinux oder config_is_read_only. Prüfung und richtige Rechte. https://daniele-michelin.com/fehler/nextcloud-csrf-check-failed/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-csrf-check-failed.png Nextcloud „CSRF check failed“ beheben · Daniele Michelin Nextcloud meldet „CSRF check failed“ beim Login oder Speichern? Meist geht die Session verloren: Cookies, Proxy, Session-Speicher, Redis prüfen. https://daniele-michelin.com/fehler/nextcloud-data-directory-readable-by-other-users/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-data-dir-readable.png Nextcloud: data directory is readable by others · Daniele Michelin Nextcloud meldet „Your data directory is readable by other users“. So setzen Sie 0770 richtig, auch auf NFS- und CIFS-Mounts, ohne den Zugriff zu brechen. https://daniele-michelin.com/fehler/nextcloud-database-is-missing-some-indexes/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-missing-indexes.png Nextcloud: Datenbank fehlen Indizes – Lösung · Daniele Michelin Nextcloud meldet „The database is missing some indexes“. So ergänzen Sie Indizes, Spalten und Primärschlüssel mit occ sicher. https://daniele-michelin.com/fehler/nextcloud-file-is-locked-423/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-423-locked.png Nextcloud „File is locked“ (423 Locked) beheben · Daniele Michelin Nextcloud meldet „is locked“ oder 423 Locked? Hängende Dateisperren nach Abbrüchen. So prüfen Sie Redis-Locking, Cron und entfernen alte Locks sicher. https://daniele-michelin.com/fehler/nextcloud-internal-server-error-request-id/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-internal-server-error.png Nextcloud Internal Server Error: Ursache finden · Daniele Michelin Nextcloud zeigt „Internal Server Error“ mit Request ID? So finden Sie den passenden Eintrag in nextcloud.log und beheben die häufigsten Ursachen gezielt. https://daniele-michelin.com/fehler/nextcloud-last-background-job-ran-ago-cron/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-cron-last-job.png Nextcloud: Last background job ran … days ago · Daniele Michelin Nextcloud meldet „Last background job execution ran … ago“? So prüfen Sie Cron-Modus, crontab von www-data und Fehler in cron.php. https://daniele-michelin.com/fehler/nextcloud-maintenance-mode-enabled/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-maintenance-mode.png Nextcloud hängt im Wartungsmodus: so beenden · Daniele Michelin Nextcloud bleibt im Wartungsmodus hängen? Meist nach abgebrochenem Update. So prüfen Sie den Status mit occ, schließen das Upgrade ab und schalten ihn aus. https://daniele-michelin.com/fehler/nextcloud-memcache-apcu-not-available-for-local-cache/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-memcache-apcu.png Nextcloud: Memcache APCu not available beheben · Daniele Michelin Nextcloud meldet bei occ oder Cron „Memcache APCu not available for local cache“: Meist fehlt apc.enable_cli=1 in der CLI-php.ini. Prüfung und Lösung. https://daniele-michelin.com/fehler/nextcloud-redisexception-redis-went-away/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-redis-went-away.png Nextcloud: Redis went away – Ursachen und Lösung · Daniele Michelin Nextcloud loggt RedisException: Redis went away, Seiten hängen oder liefern 500. Redis ist aus, Socket oder Rechte falsch, oder RAM voll. Prüfung und Lösung. https://daniele-michelin.com/fehler/nextcloud-reverse-proxy-header-configuration-incorrect/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-reverse-proxy-header.png Nextcloud: Reverse-Proxy-Header falsch – Lösung · Daniele Michelin Nextcloud meldet eine falsche Reverse-Proxy-Header-Konfiguration. So setzt du trusted_proxies und die Header hinter nginx, Traefik oder Cloudflare. https://daniele-michelin.com/fehler/nextcloud-saml-signature-validation-failed/ https://daniele-michelin.com/assets/og/kb/de-e-saml-signature-validation-failed.png SAML: Signature validation failed in Nextcloud · Daniele Michelin Nextcloud user_saml meldet „Signature validation failed. SAML Response rejected“? Meist ein rotiertes IdP-Zertifikat. Ursachen, Prüfung und Lösung. https://daniele-michelin.com/fehler/nextcloud-some-files-have-not-passed-the-integrity-check/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-integrity-check-failed.png Nextcloud: Integritätsprüfung fehlgeschlagen · Daniele Michelin Nextcloud listet INVALID_HASH, MISSING_FILE oder EXTRA_FILE nach der Integritätsprüfung. Reste eines manuellen Updates oder geänderte Dateien. Lesen und beheben. https://daniele-michelin.com/fehler/nextcloud-too-many-requests-brute-force-protection/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-too-many-requests.png Nextcloud: Too many requests – Brute-Force-Schutz · Daniele Michelin Nextcloud zeigt Too many requests from your network. Der Brute-Force-Schutz bremst eine IP. Zurücksetzen, Büro eintragen, geteilte Proxy-IP beheben. https://daniele-michelin.com/fehler/nextcloud-trusted-domain-error/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-trusted-domain.png Nextcloud: nicht vertrauenswürdige Domain – Lösung · Daniele Michelin „Zugriff über eine nicht vertrauenswürdige Domain“ in Nextcloud: Hostname fehlt in trusted_domains. So tragen Sie ihn per occ ein und prüfen den Proxy. https://daniele-michelin.com/fehler/nextcloud-updates-between-multiple-major-versions-unsupported/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-multiple-major-versions-unsupported.png Nextcloud: Update über mehrere Hauptversionen · Daniele Michelin occ upgrade oder der Updater bricht ab: Updates über mehrere Hauptversionen und Downgrades werden nicht unterstützt. Schritt für Schritt oder Code und DB angleichen. https://daniele-michelin.com/fehler/nextcloud-well-known-caldav-carddav-not-set-up/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-well-known-caldav-carddav.png Nextcloud: /.well-known/caldav nicht eingerichtet · Daniele Michelin Nextcloud warnt, dass der Webserver /.well-known/caldav oder carddav nicht auflöst. 301-Weiterleitung auf /remote.php/dav in nginx oder Apache ergänzen. Lösung. https://daniele-michelin.com/fehler/nextcloud-your-data-directory-is-invalid-ocdata/ https://daniele-michelin.com/assets/og/kb/de-e-nextcloud-data-directory-invalid.png Nextcloud: Datenverzeichnis ungültig – Lösung · Daniele Michelin Nextcloud meldet, dein Datenverzeichnis sei ungültig, und verlangt .ocdata. Datenträger nicht eingehängt, Pfad falsch oder Datei verloren. Prüfung und Lösung. https://daniele-michelin.com/fehler/nginx-bind-address-already-in-use/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-address-in-use.png nginx: bind() failed (98), Adresse schon belegt · Daniele Michelin nginx startet nicht: bind() to 0.0.0.0:80 failed (98: Address already in use). So findest du den Prozess, der den Port belegt, und behebst es in einer Minute. https://daniele-michelin.com/fehler/nginx-connect-failed-111-connection-refused-upstream/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-connection-refused-111.png nginx: connect() failed (111: Connection refused) · Daniele Michelin nginx meldet „connect() failed (111: Connection refused) while connecting to upstream“: Backend läuft nicht oder lauscht woanders. Prüfung und Lösung. https://daniele-michelin.com/fehler/nginx-could-not-build-server-names-hash/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-server-names-hash.png nginx: could not build server_names_hash – Lösung · Daniele Michelin nginx -t schlägt mit could not build server_names_hash fehl, you should increase server_names_hash_bucket_size. Ursache und die genaue Einstellung zum Ändern. https://daniele-michelin.com/fehler/nginx-emerg-cannot-load-certificate-pem-no-start-line/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-cannot-load-certificate.png nginx: [emerg] cannot load certificate – Lösung · Daniele Michelin nginx -t scheitert mit cannot load certificate, no start line oder key values mismatch. Falscher Pfad, falsche Datei oder fremder Schlüssel. Prüfung und Lösung. https://daniele-michelin.com/fehler/nginx-php-fpm-primary-script-unknown-file-not-found/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-primary-script-unknown.png nginx PHP-FPM: Primary script unknown – Lösung · Daniele Michelin nginx zeigt „File not found.“ und im Log „Primary script unknown“: PHP-FPM findet das Skript nicht. SCRIPT_FILENAME, root und Pfade in Containern prüfen. https://daniele-michelin.com/fehler/nginx-php-fpm-socket-13-permission-denied/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-fpm-socket-permission-denied.png nginx: PHP-FPM-Socket (13: Permission denied) · Daniele Michelin nginx liefert 502 und loggt connect() to unix:/run/php/...sock failed (13: Permission denied). Der nginx-Benutzer darf den PHP-FPM-Socket nicht nutzen. Lösung. https://daniele-michelin.com/fehler/nginx-rewrite-or-internal-redirection-cycle/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-rewrite-redirection-cycle.png nginx: internal redirection cycle – Lösung · Daniele Michelin nginx loggt rewrite or internal redirection cycle und antwortet 500. try_files zeigt auf eine fehlende index.html oder das root ist falsch. Lösung. https://daniele-michelin.com/fehler/nginx-upstream-prematurely-closed-connection/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-upstream-prematurely-closed.png nginx: upstream prematurely closed connection – Lösung nginx antwortet mit 502 und loggt upstream prematurely closed connection. Das Backend ist abgestürzt, neu gestartet oder spricht ein anderes Protokoll. https://daniele-michelin.com/fehler/nginx-upstream-sent-too-big-header/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-too-big-header.png nginx: upstream sent too big header – Lösung · Daniele Michelin nginx meldet „upstream sent too big header“ und liefert 502? Die Header des Backends passen nicht in den Puffer. So erhöhen Sie fastcgi- und proxy-Buffer. https://daniele-michelin.com/fehler/nginx-upstream-timed-out-110/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-upstream-timed-out.png nginx: upstream timed out (110) – Lösung · Daniele Michelin nginx loggt upstream timed out (110: Connection timed out), Nutzer sehen 504. So findest du das langsame Backend und setzt das richtige Timeout. https://daniele-michelin.com/fehler/nginx-worker-connections-are-not-enough/ https://daniele-michelin.com/assets/og/kb/de-e-nginx-worker-connections.png nginx: worker_connections are not enough – Lösung · Daniele Michelin nginx loggt worker_connections are not enough, Anfragen scheitern oder hängen. Das Verbindungslimit pro Worker ist erreicht. Limits prüfen und sicher erhöhen. https://daniele-michelin.com/fehler/oidc-invalid-client-client-authentication-failed/ https://daniele-michelin.com/assets/og/kb/de-e-oidc-invalid-client.png OIDC: invalid_client am Token-Endpunkt · Daniele Michelin OIDC-Login scheitert mit invalid_client. Falsches oder abgelaufenes Client-Secret, falsche Auth-Methode oder unbekannte Client-ID. Prüfung und Lösung. https://daniele-michelin.com/fehler/oidc-invalid-grant-token-endpoint/ https://daniele-michelin.com/assets/og/kb/de-e-oidc-invalid-grant.png OIDC invalid_grant: Ursachen & Lösung · Daniele Michelin OIDC-Fehler „invalid_grant“ am Token-Endpoint: abgelaufener oder doppelt genutzter Code, abweichende redirect_uri, widerrufener Refresh-Token, Uhrzeit. https://daniele-michelin.com/fehler/oidc-redirect-uri-mismatch-invalid-redirect-uri/ https://daniele-michelin.com/assets/og/kb/de-e-oidc-redirect-uri-mismatch.png OIDC redirect_uri_mismatch: Ursache & Lösung · Daniele Michelin OIDC-Fehler „redirect_uri_mismatch“ oder „Invalid parameter: redirect_uri“: Die Callback-URL passt nicht zur Registrierung beim IdP. https://daniele-michelin.com/fehler/php-allowed-memory-size-exhausted/ https://daniele-michelin.com/assets/og/kb/de-e-php-memory-exhausted.png PHP: Allowed memory size exhausted – Lösung · Daniele Michelin PHP Fatal error: Allowed memory size exhausted. memory_limit in der richtigen php.ini erhöhen (FPM oder CLI) und den Speicherfresser finden. https://daniele-michelin.com/fehler/php-call-to-undefined-function-mysqli-connect/ https://daniele-michelin.com/assets/og/kb/de-e-php-mysqli-undefined-function.png PHP: Call to undefined function mysqli_connect() – Lösung PHP bricht mit Call to undefined function mysqli_connect() ab (oder Class mysqli not found). Die mysqli-Erweiterung ist für die genutzte PHP-Version nicht geladen. https://daniele-michelin.com/fehler/php-cannot-modify-header-information-headers-already-sent/ https://daniele-michelin.com/assets/og/kb/de-e-php-headers-already-sent.png PHP: Cannot modify header information – Lösung · Daniele Michelin PHP warnt Cannot modify header information - headers already sent by. Vor header() oder session_start() kam Ausgabe, ein BOM oder Leerraum. So findest du es. https://daniele-michelin.com/fehler/php-fpm-server-reached-pm-max-children/ https://daniele-michelin.com/assets/og/kb/de-e-php-fpm-max-children.png PHP-FPM: server reached pm.max_children – Lösung · Daniele Michelin PHP-FPM loggt server reached pm.max_children, die Seite wird langsam oder liefert 502/504. Pool nach RAM dimensionieren und langsame Anfragen finden. https://daniele-michelin.com/fehler/php-maximum-execution-time-exceeded/ https://daniele-michelin.com/assets/og/kb/de-e-php-max-execution-time.png PHP: Maximum execution time exceeded – Lösung · Daniele Michelin PHP Fatal error: Maximum execution time of 30 seconds exceeded. max_execution_time sicher erhöhen, auch das nginx-Timeout prüfen und den langsamen Teil beheben. https://daniele-michelin.com/fehler/php-parse-error-unexpected-token/ https://daniele-michelin.com/assets/og/kb/de-e-php-parse-error-unexpected-token.png PHP: Parse error unexpected token · Daniele Michelin PHP Parse error: unexpected token heißt: Die Datei ist syntaktisch kaputt – oft nach einem PHP-Upgrade, einem abgebrochenen Upload oder einem fehlenden Semikolon. https://daniele-michelin.com/fehler/php-uploaded-file-exceeds-upload-max-filesize/ https://daniele-michelin.com/assets/og/kb/de-e-php-upload-max-filesize.png PHP: uploaded file exceeds upload_max_filesize – Lösung Uploads scheitern mit The uploaded file exceeds the upload_max_filesize directive in php.ini. Welche Limits in PHP und nginx du wo erhöhen musst. https://daniele-michelin.com/fehler/portfreigabe-geht-nicht/ https://daniele-michelin.com/assets/og/kb/de-e-portfreigabe-geht-nicht.png Portfreigabe funktioniert nicht – Ursachen & Check · Daniele Michelin Portfreigabe im Router, aber von außen nichts erreichbar? Häufig sind DS-Lite oder CGNAT schuld, sonst Firewall oder falsche Adresse. Prüfung Schritt für Schritt. https://daniele-michelin.com/fehler/postfix-deferred-connect-connection-timed-out/ https://daniele-michelin.com/assets/og/kb/de-e-postfix-connection-timed-out.png Postfix: Connection timed out, Mail zurückgestellt · Daniele Michelin Postfix status=deferred (connect to ...:25: Connection timed out). Port 25 gesperrt, Firewall oder IPv6-Problem. Prüfungen und Lösungen mit Relay über 587. https://daniele-michelin.com/fehler/postfix-host-or-domain-name-not-found-name-service-error/ https://daniele-michelin.com/assets/og/kb/de-e-postfix-host-not-found.png Postfix: Host or domain name not found – Lösung · Daniele Michelin Postfix status=deferred: Host or domain name not found, Name service error type=MX. Resolver, Chroot oder Empfängerdomain prüfen. Lösungen. https://daniele-michelin.com/fehler/postfix-hostname-does-not-resolve-to-address/ https://daniele-michelin.com/assets/og/kb/de-e-postfix-hostname-does-not-resolve.png Postfix: hostname löst nicht zur Adresse auf · Daniele Michelin Postfix-Warnung „hostname does not resolve to address“: Reverse- und Forward-DNS passen nicht. Wann das harmlos ist und wann Sie handeln müssen. https://daniele-michelin.com/fehler/postfix-mail-for-domain-loops-back-to-myself/ https://daniele-michelin.com/assets/og/kb/de-e-postfix-mail-loops-back-to-myself.png Postfix: mail loops back to myself – Lösung · Daniele Michelin Postfix weist ab: mail for example.com loops back to myself. MX oder Relay zeigt auf diesen Server, die Domain ist hier nicht eingerichtet. Schleife finden, beheben. https://daniele-michelin.com/fehler/postfix-sasl-authentication-failed-no-mechanism-available/ https://daniele-michelin.com/assets/og/kb/de-e-postfix-sasl-authentication-failed.png Postfix: SASL-Anmeldung fehlgeschlagen – Lösung · Daniele Michelin Postfix meldet SASL authentication failed, no mechanism available. Fehlende libsasl2-Module, falsche sasl_passwd oder TLS. Prüfung und Lösung. https://daniele-michelin.com/fehler/postgres-too-many-clients/ https://daniele-michelin.com/assets/og/kb/de-e-postgres-too-many-clients.png Postgres: FATAL too many clients already · Daniele Michelin „sorry, too many clients already“ heißt: max_connections ist erschöpft. Meist sind es offene Pools, ein Leak oder idle-Transaktionen – so misst du es. https://daniele-michelin.com/fehler/postgresql-fatal-no-pg-hba-conf-entry-for-host/ https://daniele-michelin.com/assets/og/kb/de-e-postgres-no-pg-hba-conf-entry.png PostgreSQL: no pg_hba.conf entry for host – Lösung · Daniele Michelin PostgreSQL antwortet mit FATAL: no pg_hba.conf entry for host. Keine Regel erlaubt Adresse, Benutzer, Datenbank oder SSL-Modus. Regeln prüfen, enge Zeile ergänzen. https://daniele-michelin.com/fehler/postgresql-fatal-password-authentication-failed/ https://daniele-michelin.com/assets/og/kb/de-e-postgres-password-authentication-failed.png PostgreSQL: password authentication failed – Lösung · Daniele Michelin PostgreSQL lehnt die Anmeldung mit FATAL: password authentication failed ab. Falsches Passwort, andere pg_hba.conf-Zeile oder Kodierung in der URL. Prüfung. https://daniele-michelin.com/fehler/redis-oom-command-not-allowed/ https://daniele-michelin.com/assets/og/kb/de-e-redis-oom-command-not-allowed.png Redis: OOM command not allowed · Daniele Michelin Redis meldet „OOM command not allowed“, weil der Speicher über maxmemory liegt und keine Keys verdrängt werden. So bleibt der Cache schreibfähig. https://daniele-michelin.com/fehler/router-neustart-richtig/ https://daniele-michelin.com/assets/og/kb/de-e-router-neustart-richtig.png Router neu starten: richtig und wann sinnvoll · Daniele Michelin Internet hängt oder WLAN spinnt? So starten Sie den Router richtig neu, prüfen mit ping, ob es half, und erkennen, wann ein Neustart nichts bringt. https://daniele-michelin.com/fehler/rsync-code-23-partial-transfer/ https://daniele-michelin.com/assets/og/kb/de-e-rsync-code-23-partial-transfer.png rsync: Fehler code 23 (some files not transferred) · Daniele Michelin rsync endet mit code 23, wenn einzelne Dateien nicht übertragen wurden: Rechte, Änderungen während des Laufs oder Attribute. Der Exitcode allein sagt wenig. https://daniele-michelin.com/fehler/saml-clock-skew-notbefore-timestamp-not-yet-valid/ https://daniele-michelin.com/assets/og/kb/de-e-saml-clock-skew.png SAML: NotBefore / Clock Skew – Zeitfehler beheben · Daniele Michelin SAML-Fehler „Could not validate timestamp: not yet valid“ oder NotBefore/NotOnOrAfter: Uhren von IdP und SP weichen ab. Prüfen und per NTP beheben. https://daniele-michelin.com/fehler/saml-invalid-audience-for-this-response/ https://daniele-michelin.com/assets/og/kb/de-e-saml-invalid-audience.png SAML: Invalid audience for this Response – Lösung · Daniele Michelin SAML-Login scheitert mit Invalid audience for this Response. Die Entity ID im IdP passt nicht zu der des Service Providers. Beide Werte vergleichen und angleichen. https://daniele-michelin.com/fehler/smart-tv-chromecast-verbindet-nicht/ https://daniele-michelin.com/assets/og/kb/de-e-smart-tv-chromecast-verbindet-nicht.png Smart-TV oder Chromecast verbindet nicht: Ursachen · Daniele Michelin Casting klappt nicht, der Fernseher oder Chromecast fehlt in der App? Gleiches Netz, Gastnetz, 2,4 GHz und Router-Einstellungen Schritt für Schritt prüfen. https://daniele-michelin.com/fehler/smtp-421-4-7-0/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-421-470.png SMTP 421 4.7.0: Rate limited – Ursachen & Lösung · Daniele Michelin SMTP 421 4.7.0 heißt: Der Empfänger drosselt Ihre IP vorübergehend. Typische Ursachen wie fehlender PTR oder Spam-Welle, Diagnose und Lösung. https://daniele-michelin.com/fehler/smtp-450-4-1-8-sender-address-rejected-domain-not-found/ https://daniele-michelin.com/assets/og/kb/de-e-postfix-sender-domain-not-found.png SMTP: 450 4.1.8 Absenderdomain nicht gefunden · Daniele Michelin Postfix lehnt mit 450 4.1.8 Sender address rejected: Domain not found ab. Die Absenderdomain hat keinen A- oder MX-Eintrag. DNS prüfen, Absender korrigieren. https://daniele-michelin.com/fehler/smtp-451-4-7-1-greylisting/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-451-471-greylisting.png SMTP 451 4.7.1 Greylisting: Ursachen & Lösung · Daniele Michelin SMTP 451 4.7.1 „Greylisted“ ist eine absichtliche Verzögerung. Wann es normal ist, wann Mails hängen bleiben und wie Sie Postgrey oder Rspamd anpassen. https://daniele-michelin.com/fehler/smtp-530-5-7-0-must-issue-starttls/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-530-570-starttls.png SMTP 530 5.7.0: Must issue STARTTLS – Lösung · Daniele Michelin SMTP 530 5.7.0: Der Server verlangt STARTTLS vor Anmeldung oder Versand. Ursachen, Prüfung mit openssl und die richtige Client-Einstellung. https://daniele-michelin.com/fehler/smtp-535-5-7-8-authentication-failed/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-535-578.png SMTP 535 5.7.8: Authentication failed beheben · Daniele Michelin SMTP 535 5.7.8 heißt: Die SMTP-Anmeldung wurde abgelehnt. Typische Ursachen bei Postfix/Dovecot, Gmail und Microsoft 365 und wie Sie sie prüfen. https://daniele-michelin.com/fehler/smtp-550-5-1-1-user-unknown/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-550-511-user-unknown.png SMTP 550 5.1.1: User unknown – Ursache & Lösung · Daniele Michelin SMTP 550 5.1.1 bedeutet: Die Empfängeradresse existiert auf dem Zielserver nicht. Tippfehler, Postfach-Maps und Domain-Klasse in Postfix prüfen. https://daniele-michelin.com/fehler/smtp-550-5-4-1-recipient-address-rejected-access-denied/ https://daniele-michelin.com/assets/og/kb/de-e-exchange-online-550-541-access-denied.png SMTP: 550 5.4.1 Recipient address rejected – Lösung · Daniele Michelin Microsoft 365 weist mit 550 5.4.1 Recipient address rejected: Access denied ab. Empfänger existiert im Tenant nicht oder Domaintyp falsch. Prüfung und Lösung. https://daniele-michelin.com/fehler/smtp-550-5-7-1/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-550-571.png SMTP 550 5.7.1: Relay access denied – Ursache & Lösung SMTP 550 5.7.1 heißt: Der Mailserver verweigert Relaying oder lehnt per Richtlinie ab. Ursachen, Prüfung mit postconf und konkrete Lösungen. https://daniele-michelin.com/fehler/smtp-550-5-7-26/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-550-5726.png SMTP 550 5.7.26 / 5.7.23: DMARC & SPF bei Gmail · Daniele Michelin Gmail lehnt mit 550 5.7.26 oder 5.7.23 ab? SPF, DKIM oder DMARC-Alignment passen nicht. So prüfen Sie die DNS-Einträge und beheben den Fehler. https://daniele-michelin.com/fehler/smtp-552-5-2-2-mailbox-full/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-552-522-mailbox-full.png SMTP 552 5.2.2: Postfach voll – Quota beheben · Daniele Michelin SMTP 552 5.2.2 heißt: Das Postfach des Empfängers hat sein Speicherlimit erreicht. So prüfen Sie die Dovecot-Quota und schaffen dauerhaft Platz. https://daniele-michelin.com/fehler/smtp-553-5-7-1-sender-address-rejected/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-553-571-sender-rejected.png SMTP 553 5.7.1: Sender address rejected beheben · Daniele Michelin SMTP 553 5.7.1 heißt: Der angemeldete Benutzer darf mit dieser Absenderadresse nicht senden. So prüfen Sie smtpd_sender_login_maps und richten Send-As ein. https://daniele-michelin.com/fehler/smtp-554-5-7-1/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-554-571.png SMTP 554 5.7.1: Blocklist-Ablehnung beheben · Daniele Michelin SMTP 554 5.7.1 mit „blocked using“: Ihre IP steht auf einer Blocklist wie Spamhaus. So finden Sie die Ursache, stoppen Spam und beantragen Delisting. https://daniele-michelin.com/fehler/smtp-554-5-7-1-relay-access-denied/ https://daniele-michelin.com/assets/og/kb/de-e-postfix-relay-access-denied.png SMTP: 554 5.7.1 Relay access denied – Lösung · Daniele Michelin Postfix antwortet 554 5.7.1 Relay access denied: Absender nicht angemeldet oder Empfängerdomain hier nicht eingerichtet. Regeln prüfen, ohne offenes Relay. https://daniele-michelin.com/fehler/smtp-port-25-gesperrt/ https://daniele-michelin.com/assets/og/kb/de-e-smtp-port-25-gesperrt.png Port 25 gesperrt: kein Mailversand möglich · Daniele Michelin Viele Provider und Clouds sperren ausgehend Port 25. Mails bleiben in der Queue, Timeouts häufen sich. Abhilfe sind Submission mit Auth oder ein Relay. https://daniele-michelin.com/fehler/speedtest-zu-langsam/ https://daniele-michelin.com/assets/og/kb/de-e-speedtest-zu-langsam.png Speedtest zeigt weniger als im Vertrag – Ursachen · Daniele Michelin Der Speedtest liegt unter dem Vertragswert? Vertrag und Praxis sind verschieden. So testen Sie per Kabel, prüfen mit ping und finden die Bremse im WLAN. https://daniele-michelin.com/fehler/ssh-connect-to-host-port-22-connection-timed-out/ https://daniele-michelin.com/assets/og/kb/de-e-ssh-connection-timed-out.png SSH Port 22: Connection timed out – Ursachen · Daniele Michelin ssh: connect to host port 22: Connection timed out. Firewall, falsche Adresse, Server aus oder fail2ban? So erkennst und behebst du es, timeout vs. refused. https://daniele-michelin.com/fehler/ssh-connection-refused-port-22/ https://daniele-michelin.com/assets/og/kb/de-e-ssh-connection-refused.png SSH: connect to host port 22 refused · Daniele Michelin SSH Connection refused heißt: Auf dem Port nimmt kein sshd Verbindungen an. Meist läuft der Dienst nicht, lauscht auf einem anderen Port oder wird abgelehnt. https://daniele-michelin.com/fehler/ssh-permission-denied-publickey/ https://daniele-michelin.com/assets/og/kb/de-e-ssh-permission-denied-publickey.png SSH: Permission denied (publickey) beheben · Daniele Michelin SSH meldet „Permission denied (publickey)“: falscher Benutzer, Schlüssel fehlt in authorized_keys, falsche Rechte oder ssh-rsa abgeschaltet. https://daniele-michelin.com/fehler/ssh-remote-host-identification-has-changed/ https://daniele-michelin.com/assets/og/kb/de-e-ssh-host-key-changed.png SSH-Warnung: Remote host identification changed · Daniele Michelin SSH warnt REMOTE HOST IDENTIFICATION HAS CHANGED. Meist ein Neuaufbau des Servers. So prüfst du den Schlüssel und korrigierst known_hosts sicher. https://daniele-michelin.com/fehler/ssh-too-many-authentication-failures/ https://daniele-michelin.com/assets/og/kb/de-e-ssh-too-many-authentication-failures.png SSH: Too many authentication failures – Lösung · Daniele Michelin SSH trennt mit Too many authentication failures, bevor du ein Passwort tippst. Der Agent bietet zu viele Schlüssel an. IdentitiesOnly nutzen. https://daniele-michelin.com/fehler/ssl-certificate-has-expired/ https://daniele-michelin.com/assets/og/kb/de-e-tls-certificate-expired.png SSL: certificate has expired – Lösung · Daniele Michelin „certificate has expired“ oder NET::ERR_CERT_DATE_INVALID: Erneuerung gescheitert, Dienst nicht neu geladen oder falsche Uhr. Prüfen und dauerhaft beheben. https://daniele-michelin.com/fehler/ssl-error-rx-record-too-long/ https://daniele-michelin.com/assets/og/kb/de-e-tls-rx-record-too-long.png SSL_ERROR_RX_RECORD_TOO_LONG: Ursache & Lösung · Daniele Michelin Firefox zeigt SSL_ERROR_RX_RECORD_TOO_LONG: Auf Port 443 antwortet der Server mit unverschlüsseltem HTTP. Meist fehlt „ssl“ in der listen-Zeile von nginx. https://daniele-michelin.com/fehler/ssl-unable-to-get-local-issuer-certificate/ https://daniele-michelin.com/assets/og/kb/de-e-tls-unable-to-get-local-issuer.png unable to get local issuer certificate: Lösung · Daniele Michelin „SSL certificate problem: unable to get local issuer certificate“ bei curl, Python oder Git: fehlende Zwischenzertifikate, CA-Bundle oder TLS-Inspection. https://daniele-michelin.com/fehler/sudo-user-is-not-in-the-sudoers-file/ https://daniele-michelin.com/assets/og/kb/de-e-sudo-not-in-sudoers.png sudo: Benutzer nicht in der sudoers-Datei · Daniele Michelin sudo meldet „is not in the sudoers file. This incident will be reported.“ Dem Benutzer fehlt die sudo-Gruppe oder eine Regel. Prüfen und ergänzen: usermod, visudo. https://daniele-michelin.com/fehler/systemd-job-failed-control-process-exited-with-error-code/ https://daniele-michelin.com/assets/og/kb/de-e-systemd-job-failed-control-process.png systemd: Job failed – control process exited · Daniele Michelin „Job for X.service failed because the control process exited with error code“: So finden Sie mit systemctl status und journalctl die echte Fehlermeldung. https://daniele-michelin.com/fehler/systemd-start-request-repeated-too-quickly/ https://daniele-michelin.com/assets/og/kb/de-e-systemd-start-limit-hit.png systemd: Start-Limit erreicht (start-limit-hit) · Daniele Michelin systemd: Start request repeated too quickly, start-limit-hit. Eine Absturzschleife hat das Limit erreicht. Ursache finden und die Unit zurücksetzen. https://daniele-michelin.com/fehler/tar-unexpected-end-of-file/ https://daniele-michelin.com/assets/og/kb/de-e-tar-unexpected-end-of-file.png tar: unexpected end of file beim Entpacken · Daniele Michelin „unexpected end of file“ heißt: Das Archiv ist unvollständig – abgebrochener Download, voller Datenträger oder Abbruch beim Erstellen. So rettest du den Rest. https://daniele-michelin.com/fehler/temporary-failure-in-name-resolution/ https://daniele-michelin.com/assets/og/kb/de-e-linux-temporary-failure-name-resolution.png Temporary failure in name resolution – Lösung · Daniele Michelin ping, apt oder curl melden Temporary failure in name resolution. Der Server erreicht keinen DNS-Resolver: leere resolv.conf, resolved down oder Port 53 blockiert. https://daniele-michelin.com/fehler/tls-err-ssl-version-or-cipher-mismatch/ https://daniele-michelin.com/assets/og/kb/de-e-tls-version-cipher-mismatch.png ERR_SSL_VERSION_OR_CIPHER_MISMATCH – Lösung · Daniele Michelin ERR_SSL_VERSION_OR_CIPHER_MISMATCH: keine gemeinsame TLS-Version oder Cipher. ssl_protocols, ssl_ciphers und Zertifikat des Virtual Hosts prüfen. https://daniele-michelin.com/fehler/wlan-bricht-ab/ https://daniele-michelin.com/assets/og/kb/de-e-wlan-bricht-ab.png WLAN bricht ab: Verbindung fällt immer wieder aus · Daniele Michelin Das WLAN trennt sich ständig oder fällt kurz aus? Einfache Ursachen wie Funkstörung, Energiesparmodus und Router-Last und eine Prüfung mit echten Befehlen. https://daniele-michelin.com/fehler/wlan-kanal-wechseln-24-5-ghz/ https://daniele-michelin.com/assets/og/kb/de-e-wlan-kanal-wechseln.png WLAN-Kanal wechseln: 2,4 oder 5 GHz wählen · Daniele Michelin Welches WLAN-Band und welcher Kanal passt? Erklärung 2,4 und 5 GHz, Kanäle 1, 6, 11, Prüfung der Nachbarnetze mit echten Befehlen und Wechsel im Router. https://daniele-michelin.com/fehler/wlan-langsam/ https://daniele-michelin.com/assets/og/kb/de-e-wlan-langsam.png WLAN langsam: Ursachen und Prüfung zu Hause · Daniele Michelin Das WLAN ist langsam, obwohl es verbunden ist? Einfache Prüfung von Entfernung, Interferenzen und Router mit echten Befehlen und typische Lösungen für zu Hause. https://daniele-michelin.com/fehler/wlan-repeater-oder-mesh/ https://daniele-michelin.com/assets/og/kb/de-e-wlan-repeater-mesh.png WLAN Repeater oder Mesh: was passt für zu Hause · Daniele Michelin Funkloch im Haus: Repeater oder Mesh? Allgemeiner Vergleich, richtige Aufstellung, Prüfung des Empfangs mit echten Befehlen und wann ein Kabel die beste Lösung ist. https://daniele-michelin.com/fehler/wlan-verbunden-kein-internet/ https://daniele-michelin.com/assets/og/kb/de-e-wlan-verbunden-kein-internet.png WLAN verbunden, aber kein Internet: Prüfung · Daniele Michelin WLAN steht, aber Webseiten laden nicht? Schritt für Schritt prüfen, ob Router, Internetleitung oder DNS die Ursache ist, mit echten Befehlen und einfachen Lösungen. https://daniele-michelin.com/fehler/zwei-router-doppel-nat/ https://daniele-michelin.com/assets/og/kb/de-e-mehrere-router-doppel-nat.png Zwei Router im Heimnetz: Doppel-NAT erklärt · Daniele Michelin Zwei Router hintereinander führen zu Doppel-NAT, Portfreigaben und Spiele-Verbindungen scheitern. So erkennen und beheben Sie das Problem. https://daniele-michelin.com/glossar/a-aaaa-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-a-aaaa.png Was ist ein A-/AAAA-Eintrag? DNS erklärt · Daniele Michelin Ein A-Eintrag verknüpft einen Hostnamen mit einer IPv4-Adresse, AAAA mit IPv6. Aufbau, Prüfung mit dig und typische Fehler bei Dual-Stack. https://daniele-michelin.com/glossar/acme/ https://daniele-michelin.com/assets/og/kb/de-g-acme.png Was ist ACME? Automatische TLS-Zertifikate · Daniele Michelin ACME ist das Protokoll, mit dem Let's Encrypt und andere CAs Zertifikate automatisch ausstellen. HTTP-01, DNS-01, Clients wie certbot und typische Fehler. https://daniele-michelin.com/glossar/autoritativer-nameserver/ https://daniele-michelin.com/assets/og/kb/de-g-authoritative.png Was ist ein autoritativer Nameserver? · Daniele Michelin Ein autoritativer Nameserver hält die Originaldaten einer DNS-Zone und liefert verbindliche Antworten. Abgrenzung zum Resolver und Prüfung mit dig. https://daniele-michelin.com/glossar/bounce-ndr/ https://daniele-michelin.com/assets/og/kb/de-g-ndr.png Was ist ein Bounce (NDR)? Fehlermails lesen · Daniele Michelin Ein Bounce oder NDR meldet, dass eine Mail nicht zugestellt wurde. Status-Codes lesen, Hard- und Soft-Bounce unterscheiden, Backscatter vermeiden. https://daniele-michelin.com/glossar/caa-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-caa.png Was ist ein CAA-Eintrag? Zertifikate absichern · Daniele Michelin Ein CAA-Eintrag legt fest, welche Zertifizierungsstellen Zertifikate für eine Domain ausstellen dürfen. Syntax, Beispiel und Fehler bei Let's Encrypt. https://daniele-michelin.com/glossar/caldav-carddav/ https://daniele-michelin.com/assets/og/kb/de-g-caldav-carddav.png Was sind CalDAV und CardDAV? Sync erklärt · Daniele Michelin CalDAV synchronisiert Kalender, CardDAV Kontakte, beide auf Basis von WebDAV. Einrichtung mit Nextcloud, iOS, Android und Thunderbird und typische Fehler. https://daniele-michelin.com/glossar/cname-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-cname.png Was ist ein CNAME-Eintrag? Alias im DNS · Daniele Michelin Ein CNAME-Eintrag macht einen Namen zum Alias eines anderen. Wann er sinnvoll ist, warum er nicht am Zonen-Apex stehen darf und typische Fehler. https://daniele-michelin.com/glossar/content-security-policy/ https://daniele-michelin.com/assets/og/kb/de-g-csp.png Was ist eine Content Security Policy (CSP)? · Daniele Michelin Die Content Security Policy legt fest, aus welchen Quellen eine Seite Skripte, Styles und Frames laden darf. Aufbau, Report-Only-Modus und typische Fehler. https://daniele-michelin.com/glossar/cron/ https://daniele-michelin.com/assets/og/kb/de-g-cron.png Was ist ein Cronjob? Cron unter Linux erklärt · Daniele Michelin Cron führt Befehle unter Linux zeitgesteuert aus. Aufbau einer Crontab-Zeile, Unterschied zu systemd-Timern und warum Cronjobs still scheitern. https://daniele-michelin.com/glossar/dkim/ https://daniele-michelin.com/assets/og/kb/de-g-dkim.png Was ist DKIM? E-Mail-Signaturen erklärt · Daniele Michelin DKIM signiert ausgehende E-Mails kryptografisch, der öffentliche Schlüssel liegt im DNS. Funktionsweise, Selector und häufige Gründe für dkim=fail. https://daniele-michelin.com/glossar/dmarc/ https://daniele-michelin.com/assets/og/kb/de-g-dmarc.png Was ist DMARC? Richtlinie und Reports erklärt · Daniele Michelin DMARC verknüpft SPF und DKIM mit der sichtbaren Absenderadresse und legt fest, was mit Fälschungen passiert. Alignment, Policies und Reports. https://daniele-michelin.com/glossar/dns-propagation/ https://daniele-michelin.com/assets/og/kb/de-g-propagation.png Was ist DNS-Propagation? Wie lange dauert sie? · Daniele Michelin DNS-Propagation ist die Zeit, bis alle Resolver eine geänderte DNS-Antwort sehen. Warum das von der TTL abhängt und wie Sie den Stand prüfen. https://daniele-michelin.com/glossar/dns-resolver/ https://daniele-michelin.com/assets/og/kb/de-g-resolver.png Was ist ein DNS-Resolver? Rekursion erklärt · Daniele Michelin Ein DNS-Resolver beantwortet Anfragen von Clients, indem er die Kette von Root bis zur Zone abfragt und das Ergebnis cacht. Funktion und Diagnose. https://daniele-michelin.com/glossar/dnssec/ https://daniele-michelin.com/assets/og/kb/de-g-dnssec.png Was ist DNSSEC? Signierte DNS-Antworten · Daniele Michelin DNSSEC signiert DNS-Einträge kryptografisch, damit Resolver Fälschungen erkennen. Funktionsweise, DS-Eintrag und warum Fehler zum Totalausfall führen. https://daniele-michelin.com/glossar/eskalation/ https://daniele-michelin.com/assets/og/kb/de-g-escalation.png Was ist eine Eskalation im IT-Support? · Daniele Michelin Eine Eskalation übergibt ein Ticket an eine höhere Support-Ebene oder informiert das Management. Funktionale und hierarchische Eskalation, gute Übergaben. https://daniele-michelin.com/glossar/file-deskriptor/ https://daniele-michelin.com/assets/og/kb/de-g-file-descriptor.png Was ist ein File-Deskriptor? Limits erklärt · Daniele Michelin Ein File-Deskriptor ist die Nummer, über die ein Prozess offene Dateien und Sockets anspricht. Woher Too many open files kommt und wie Sie Limits anheben. https://daniele-michelin.com/glossar/glue-record/ https://daniele-michelin.com/assets/og/kb/de-g-glue.png Was ist ein Glue-Record? DNS-Delegation · Daniele Michelin Glue-Records sind IP-Adressen von Nameservern, die in der übergeordneten Zone stehen. Wann Sie sie brauchen und wie fehlende Glue-Records auffallen. https://daniele-michelin.com/glossar/greylisting/ https://daniele-michelin.com/assets/og/kb/de-g-greylisting.png Was ist Greylisting? Spamschutz mit Verzögerung · Daniele Michelin Greylisting lehnt Mails unbekannter Absender zunächst vorübergehend ab und nimmt sie beim zweiten Versuch an. Wirkung, Nachteile und typische Fehler. https://daniele-michelin.com/glossar/hsts/ https://daniele-michelin.com/assets/og/kb/de-g-hsts.png Was ist HSTS? HTTP Strict Transport Security · Daniele Michelin HSTS weist Browser an, eine Domain nur noch per HTTPS aufzurufen. Header-Syntax, max-age, includeSubDomains, Preload und das Risiko beim Zurückrollen. https://daniele-michelin.com/glossar/http-statuscode/ https://daniele-michelin.com/assets/og/kb/de-g-http-status.png Was ist ein HTTP-Statuscode? Klassen erklärt · Daniele Michelin HTTP-Statuscodes zeigen, wie ein Server eine Anfrage beantwortet hat. Die fünf Klassen, wichtige Codes wie 301, 403, 502 und wie Sie sie richtig lesen. https://daniele-michelin.com/glossar/identity-provider/ https://daniele-michelin.com/assets/og/kb/de-g-idp.png Was ist ein Identity Provider (IdP)? · Daniele Michelin Ein Identity Provider verwaltet Benutzerkonten und bestätigt Anwendungen per SAML oder OIDC, wer angemeldet ist. Beispiele, Aufgaben und Ausfallrisiken. https://daniele-michelin.com/glossar/imap/ https://daniele-michelin.com/assets/og/kb/de-g-imap.png Was ist IMAP? Postfach-Zugriff erklärt · Daniele Michelin IMAP ist das Protokoll, mit dem Mailprogramme auf ein Postfach auf dem Server zugreifen. Unterschied zu POP3, Ports 143 und 993 und typische Probleme. https://daniele-michelin.com/glossar/ https://daniele-michelin.com/assets/og/kb/de-hub-glossary.png IT-Glossar für Admins: DNS, Mail, TLS, SSO · Daniele Michelin Begriffe aus DNS, E-Mail, TLS, Single Sign-on und Linux-Betrieb kurz und praxisnah erklärt — mit Beispielen und Befehlen. https://daniele-michelin.com/glossar/inode/ https://daniele-michelin.com/assets/og/kb/de-g-inode.png Was ist ein Inode? Linux-Dateisystem erklärt · Daniele Michelin Ein Inode speichert die Metadaten einer Datei im Linux-Dateisystem. Warum ein Datenträger trotz freiem Platz voll sein kann und wie Sie das prüfen. https://daniele-michelin.com/glossar/journald/ https://daniele-michelin.com/assets/og/kb/de-g-journald.png Was ist journald? Logs unter systemd lesen · Daniele Michelin journald sammelt unter systemd die Logs aller Dienste in einem binären Journal. Wichtige journalctl-Befehle, Speicherlimit und dauerhafte Speicherung. https://daniele-michelin.com/glossar/json-web-token/ https://daniele-michelin.com/assets/og/kb/de-g-jwt.png Was ist ein JWT? JSON Web Token erklärt · Daniele Michelin Ein JWT ist ein signiertes Token aus Header, Payload und Signatur, genutzt bei OIDC und APIs. Aufbau, Prüfung, Ablaufzeit und typische Sicherheitsfehler. https://daniele-michelin.com/glossar/logrotate/ https://daniele-michelin.com/assets/og/kb/de-g-logrotate.png Was ist logrotate? Logdateien rotieren · Daniele Michelin logrotate rotiert, komprimiert und löscht alte Logdateien automatisch. Aufbau einer Konfiguration, copytruncate gegen postrotate und typische Fehler. https://daniele-michelin.com/glossar/mta-mail-transfer-agent/ https://daniele-michelin.com/assets/og/kb/de-g-mta.png Was ist ein MTA? Mail Transfer Agent erklärt · Daniele Michelin Ein MTA nimmt E-Mails per SMTP an und stellt sie an den nächsten Server zu, etwa Postfix oder Exim. Abgrenzung zu MUA und MDA und die Rolle der Queue. https://daniele-michelin.com/glossar/mta-sts/ https://daniele-michelin.com/assets/og/kb/de-g-mta-sts.png Was ist MTA-STS? TLS-Pflicht für Mailserver · Daniele Michelin MTA-STS zwingt sendende Mailserver zu verschlüsselter Zustellung mit gültigem Zertifikat. Aufbau aus TXT-Eintrag und Policy-Datei, Modi und Fehler. https://daniele-michelin.com/glossar/multi-faktor-authentifizierung/ https://daniele-michelin.com/assets/og/kb/de-g-mfa.png Was ist MFA? Multi-Faktor-Authentifizierung · Daniele Michelin MFA verlangt bei der Anmeldung neben dem Passwort einen zweiten Faktor wie App-Code, Push oder Sicherheitsschlüssel. Verfahren, Schwächen, Support. https://daniele-michelin.com/glossar/mx-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-mx.png Was ist ein MX-Eintrag? Mail-Routing im DNS · Daniele Michelin Der MX-Eintrag legt fest, welcher Server E-Mails für eine Domain annimmt. Priorität, Prüfung mit dig und die häufigsten Fehler bei der Umstellung. https://daniele-michelin.com/glossar/nextcloud/ https://daniele-michelin.com/assets/og/kb/de-g-nextcloud.png Was ist Nextcloud? Aufbau für Admins erklärt · Daniele Michelin Nextcloud ist eine selbst gehostete Plattform für Dateien, Kalender, Kontakte und Zusammenarbeit. Aufbau aus PHP, Datenbank, Cache und Speicher, Betrieb. https://daniele-michelin.com/glossar/ns-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-ns.png Was ist ein NS-Eintrag? Delegation im DNS · Daniele Michelin NS-Einträge legen fest, welche Nameserver für eine Zone zuständig sind. Delegation bei der Registry, Prüfung mit dig und Fehler beim Anbieterwechsel. https://daniele-michelin.com/glossar/nxdomain/ https://daniele-michelin.com/assets/og/kb/de-g-nxdomain.png Was bedeutet NXDOMAIN? DNS-Fehler erklärt · Daniele Michelin NXDOMAIN heißt: Den abgefragten Namen gibt es im DNS nicht. Unterschied zu NOERROR ohne Daten und SERVFAIL, Ursachen und Diagnose mit dig. https://daniele-michelin.com/glossar/oauth-2-0/ https://daniele-michelin.com/assets/og/kb/de-g-oauth2.png Was ist OAuth 2.0? Autorisierung erklärt · Daniele Michelin OAuth 2.0 erlaubt Anwendungen Zugriff auf Ressourcen, ohne das Passwort des Nutzers zu kennen. Rollen, Access- und Refresh-Token und gängige Flows. https://daniele-michelin.com/glossar/oom-killer/ https://daniele-michelin.com/assets/og/kb/de-g-oom-killer.png Was ist der OOM-Killer? Speichermangel erklärt · Daniele Michelin Der OOM-Killer beendet unter Linux Prozesse, wenn der Arbeitsspeicher ausgeht. Wie er sein Opfer wählt, wie Sie ihn im Log finden und was dagegen hilft. https://daniele-michelin.com/glossar/openid-connect/ https://daniele-michelin.com/assets/og/kb/de-g-oidc.png Was ist OpenID Connect (OIDC)? Erklärt · Daniele Michelin OpenID Connect ergänzt OAuth 2.0 um Anmeldung und Identität. ID-Token, Discovery-Dokument, Client-ID und Redirect-URI und typische Fehler beim Einrichten. https://daniele-michelin.com/glossar/php-fpm/ https://daniele-michelin.com/assets/og/kb/de-g-php-fpm.png Was ist PHP-FPM? Pools und Tuning erklärt · Daniele Michelin PHP-FPM führt PHP-Code in einem eigenen Prozesspool aus, den nginx oder Apache per FastCGI anspricht. Pool-Einstellungen, pm.max_children und Fehler. https://daniele-michelin.com/glossar/ptr-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-ptr.png Was ist ein PTR-Eintrag? Reverse DNS erklärt · Daniele Michelin Ein PTR-Eintrag löst eine IP-Adresse zurück in einen Hostnamen auf. Warum Mailserver ihn brauchen, wer ihn setzt und wie Sie ihn mit dig prüfen. https://daniele-michelin.com/glossar/relay-open-relay/ https://daniele-michelin.com/assets/og/kb/de-g-open-relay.png Was ist ein Mail-Relay? Open Relay erklärt · Daniele Michelin Ein Relay leitet E-Mails an fremde Domains weiter. Wann das gewollt ist, was ein Open Relay gefährlich macht und woher Relay access denied kommt. https://daniele-michelin.com/glossar/reverse-proxy/ https://daniele-michelin.com/assets/og/kb/de-g-reverse-proxy.png Was ist ein Reverse Proxy? Aufgaben erklärt · Daniele Michelin Ein Reverse Proxy nimmt Anfragen entgegen und leitet sie an Backend-Server weiter, etwa nginx vor Nextcloud. Aufgaben, Header und typische Fehler. https://daniele-michelin.com/glossar/root-cause-analysis/ https://daniele-michelin.com/assets/og/kb/de-g-rca.png Was ist eine Root Cause Analysis (RCA)? · Daniele Michelin Eine Root Cause Analysis sucht nach einer Störung die eigentliche Ursache statt nur des Symptoms. Ablauf, 5-Why-Methode und guter Bericht. https://daniele-michelin.com/glossar/rpo-rto/ https://daniele-michelin.com/assets/og/kb/de-g-rpo-rto.png Was sind RPO und RTO? Ziele für Wiederherstellung · Daniele Michelin RPO legt fest, wie viel Datenverlust tragbar ist, RTO, wie schnell ein System wieder laufen muss. Beispiele, Abhängigkeiten und warum Restore-Tests zählen. https://daniele-michelin.com/glossar/s3-object-storage/ https://daniele-michelin.com/assets/og/kb/de-g-s3.png Was ist S3 Object Storage? Bucket erklärt · Daniele Michelin S3 Object Storage speichert Daten als Objekte in Buckets und wird per HTTP-API angesprochen. Unterschied zum Dateisystem, Einsatz mit Nextcloud, Fehler. https://daniele-michelin.com/glossar/saml/ https://daniele-michelin.com/assets/og/kb/de-g-saml.png Was ist SAML? SSO-Protokoll erklärt · Daniele Michelin SAML 2.0 ist ein XML-basiertes Protokoll für Single Sign-on zwischen Identity Provider und Anwendung. Ablauf, Metadaten, Zertifikate und typische Fehler. https://daniele-michelin.com/glossar/scim/ https://daniele-michelin.com/assets/og/kb/de-g-scim.png Was ist SCIM? Benutzer-Provisioning erklärt · Daniele Michelin SCIM synchronisiert Benutzer und Gruppen automatisch vom Identity Provider in Anwendungen. Unterschied zu SSO, Ablauf und typische Stolpersteine. https://daniele-michelin.com/glossar/server-name-indication/ https://daniele-michelin.com/assets/og/kb/de-g-sni.png Was ist SNI? Server Name Indication erklärt · Daniele Michelin SNI teilt dem Server beim TLS-Handshake mit, welcher Hostname gemeint ist, damit mehrere HTTPS-Sites eine IP teilen. Funktion und typische Fehlerbilder. https://daniele-michelin.com/glossar/service-level-agreement/ https://daniele-michelin.com/assets/og/kb/de-g-sla.png Was ist ein SLA? Service Level Agreement · Daniele Michelin Ein SLA legt messbare Leistungen wie Reaktionszeit, Lösungszeit und Verfügbarkeit fest. Begriffe, was 99,9 % wirklich bedeuten und typische Fallstricke. https://daniele-michelin.com/glossar/service-provider/ https://daniele-michelin.com/assets/og/kb/de-g-sp.png Was ist ein Service Provider (SP) bei SSO? · Daniele Michelin Im SSO ist der Service Provider die Anwendung, die dem Identity Provider vertraut, etwa Nextcloud mit SAML. Entity-ID, ACS-URL und typische Fehler. https://daniele-michelin.com/glossar/single-sign-on/ https://daniele-michelin.com/assets/og/kb/de-g-sso.png Was ist Single Sign-on (SSO)? Kurz erklärt · Daniele Michelin Mit SSO melden sich Nutzer einmal beim Identity Provider an und erreichen damit mehrere Anwendungen. Protokolle, Vorteile und typische Stolpersteine. https://daniele-michelin.com/glossar/smtp/ https://daniele-michelin.com/assets/og/kb/de-g-smtp.png Was ist SMTP? Mailversand einfach erklärt · Daniele Michelin SMTP ist das Protokoll, mit dem Mailserver E-Mails untereinander zustellen. Ablauf einer Sitzung, Ports 25, 587 und 465 und typische Fehlercodes. https://daniele-michelin.com/glossar/snapshot-vs-backup/ https://daniele-michelin.com/assets/og/kb/de-g-snapshot-backup.png Snapshot oder Backup? Der Unterschied · Daniele Michelin Ein Snapshot friert den Zustand eines Datenträgers ein, ein Backup ist eine unabhängige Kopie an anderem Ort. Warum Snapshots allein kein Backup sind. https://daniele-michelin.com/glossar/soa-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-soa.png Was ist ein SOA-Eintrag? Felder erklärt · Daniele Michelin Der SOA-Eintrag steht am Anfang jeder DNS-Zone. Was Serial, Refresh, Retry, Expire und Minimum bedeuten und warum die Seriennummer wichtig ist. https://daniele-michelin.com/glossar/spf/ https://daniele-michelin.com/assets/og/kb/de-g-spf.png Was ist SPF? Sender Policy Framework erklärt · Daniele Michelin SPF legt per TXT-Eintrag fest, welche Server Mails für eine Domain senden dürfen. Syntax, die Grenze von 10 DNS-Lookups und typische Fehler. https://daniele-michelin.com/glossar/srv-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-srv.png Was ist ein SRV-Eintrag? Dienste im DNS finden · Daniele Michelin Ein SRV-Eintrag nennt Host und Port eines Dienstes, etwa für Autodiscover, CalDAV, SIP oder XMPP. Aufbau der Felder, Beispiel und Prüfung mit dig. https://daniele-michelin.com/glossar/starttls/ https://daniele-michelin.com/assets/og/kb/de-g-starttls.png Was ist STARTTLS? Verschlüsselung nachrüsten · Daniele Michelin STARTTLS schaltet eine unverschlüsselte SMTP-, IMAP- oder POP3-Verbindung auf TLS um. Ablauf, Unterschied zu implizitem TLS und typische Schwächen. https://daniele-michelin.com/glossar/subject-alternative-name/ https://daniele-michelin.com/assets/og/kb/de-g-san.png Was ist ein SAN? Subject Alternative Name · Daniele Michelin Der Subject Alternative Name listet alle Hostnamen, für die ein TLS-Zertifikat gilt. Warum der Common Name nicht mehr zählt und wie Sie SANs prüfen. https://daniele-michelin.com/glossar/submission-port-587/ https://daniele-michelin.com/assets/og/kb/de-g-submission.png Was ist Submission? Port 587 vs. 25 und 465 · Daniele Michelin Submission ist der SMTP-Dienst für den Versand durch Mailprogramme und Anwendungen. Unterschied zu Port 25 und 465 und warum Anmeldung Pflicht ist. https://daniele-michelin.com/glossar/support-level-1st-2nd-3rd/ https://daniele-michelin.com/assets/og/kb/de-g-support-levels.png 1st, 2nd, 3rd Level Support: Unterschiede · Daniele Michelin Die Support-Level teilen Anfragen nach Komplexität auf: Annahme und Standardfälle, technische Analyse, Entwicklung und Hersteller. Aufgaben und Übergaben. https://daniele-michelin.com/glossar/systemd-unit/ https://daniele-michelin.com/assets/og/kb/de-g-systemd-unit.png Was ist eine systemd-Unit? Aufbau erklärt · Daniele Michelin Eine systemd-Unit beschreibt einen Dienst, Timer oder Mount, den systemd verwaltet. Aufbau der Unit-Datei, Overrides und wie Sie Startfehler finden. https://daniele-michelin.com/glossar/tls/ https://daniele-michelin.com/assets/og/kb/de-g-tls.png Was ist TLS? Transport Layer Security erklärt · Daniele Michelin TLS verschlüsselt Verbindungen wie HTTPS, IMAPS und SMTP und prüft per Zertifikat die Identität des Servers. Handshake, Versionen und typische Fehler. https://daniele-michelin.com/glossar/ttl/ https://daniele-michelin.com/assets/og/kb/de-g-ttl.png Was ist die TTL im DNS? Time to Live erklärt · Daniele Michelin Die TTL legt fest, wie lange Resolver einen DNS-Eintrag zwischenspeichern. Sinnvolle Werte, TTL vor einer Migration senken und typische Irrtümer. https://daniele-michelin.com/glossar/txt-eintrag/ https://daniele-michelin.com/assets/og/kb/de-g-txt.png Was ist ein TXT-Eintrag? Einsatz und Grenzen · Daniele Michelin TXT-Einträge speichern freien Text im DNS und tragen SPF, DKIM, DMARC und Domain-Verifizierungen. Aufbau, 255-Zeichen-Grenze und häufige Fehler. https://daniele-michelin.com/glossar/webdav/ https://daniele-michelin.com/assets/og/kb/de-g-webdav.png Was ist WebDAV? Dateizugriff über HTTP · Daniele Michelin WebDAV erweitert HTTP um Methoden zum Lesen, Schreiben und Verwalten von Dateien auf einem Server. Einsatz bei Nextcloud, Clients und typische Fehler. https://daniele-michelin.com/glossar/zertifikatskette/ https://daniele-michelin.com/assets/og/kb/de-g-cert-chain.png Was ist eine Zertifikatskette? Intermediate · Daniele Michelin Die Zertifikatskette verbindet Ihr Serverzertifikat über Zwischenzertifikate mit einer vertrauenswürdigen Root-CA. Warum fullchain wichtig ist. https://daniele-michelin.com/it/blog/analisi-causa-radice-supporto/ https://daniele-michelin.com/assets/og/analisi-causa-radice-supporto.png Analisi della causa nel supporto: sintomo ≠ causa Un workaround chiude il ticket, solo l'analisi della causa evita il prossimo. Come nel supporto di 2° e 3° livello si passa dal sintomo alla causa vera. https://daniele-michelin.com/it/blog/assistente-ai-per-il-proprio-sito/ https://daniele-michelin.com/assets/og/assistente-ai-per-il-proprio-sito.png Un assistente AI per il proprio sito: chat e voce, ospitato in casa Come un receptionist AI locale è diventato l'assistente del mio sito: widget, proxy nginx, voce sul Mac, prenotazioni e privacy. https://daniele-michelin.com/it/blog/classifica-falsificazione-email-102-domini/ https://daniele-michelin.com/assets/og/classifica-falsificazione-email-102-domini.png Questi domini si possono falsificare? SPF e DMARC di 102 siti SPF, DMARC e MTA-STS di 102 domini noti: 59 rifiutano la posta falsificata, 21 osservano soltanto con p=none, 6 non hanno DMARC. Banche, Germania e Italia. https://daniele-michelin.com/it/blog/controllare-nextcloud-dallesterno/ https://daniele-michelin.com/assets/og/controllare-nextcloud-dallesterno.png Controllare Nextcloud dall'esterno: versione, EOL, percorsi esposti Uno strumento che valuta la tua Nextcloud dalla rete vera: versione, end of life, percorsi esposti (config, data, .htaccess) e header di sicurezza. Senza login. https://daniele-michelin.com/it/blog/halloween-mostro-dei-token-immagine-video/ https://daniele-michelin.com/assets/og/halloween-mostro-dei-token-immagine-video.png Halloween: il mostro dei token preferisce i video Un'immagine di Halloween o un breve video AI? Un esempio concreto: 1.120 contro 28.960 token di output. E perché il rapporto non racconta tutta la spesa. https://daniele-michelin.com/it/blog/header-di-sicurezza-set-base/ https://daniele-michelin.com/assets/og/header-di-sicurezza-set-base.png Header di sicurezza HTTP: set base per nginx HSTS, CSP, X-Content-Type-Options, Referrer-Policy, Permissions-Policy: cosa fa ogni header di sicurezza, un set base nginx da copiare e come testarlo. https://daniele-michelin.com/it/blog/header-sicurezza-57-siti/ https://daniele-michelin.com/assets/og/header-sicurezza-57-siti.png Abbiamo valutato gli header di sicurezza di 57 grandi siti Controllo di 57 siti noti: HSTS è diffuso, la CSP no. Risultati per header, i quattro siti con voto A e come leggere i numeri in modo corretto. https://daniele-michelin.com/it/blog/migrazione-dns-senza-downtime/ https://daniele-michelin.com/assets/og/migrazione-dns-senza-downtime.png Migrazione DNS senza downtime: TTL, export zona, checklist Cambiare hosting o provider DNS senza perdere sito ed e-mail: abbassa il TTL, esporta la zona invece di ricopiarla, testa prima dello switch — con checklist. https://daniele-michelin.com/it/blog/n8n-cartolina-orbita/ https://daniele-michelin.com/assets/og/n8n-cartolina-orbita.png Vetrina n8n: una cartolina dall'orbita Premi un pulsante, ricevi una cartolina: n8n trova la ISS, scarica l'immagine NASA del punto sotto e un'AI scrive il testo. Con il workflow da scaricare. https://daniele-michelin.com/it/blog/n8n-citta-del-sito/ https://daniele-michelin.com/assets/og/n8n-citta-del-sito.png Il tuo sito come città: un workflow n8n Inserisci un dominio ed esplora la città in 3D: le sezioni diventano quartieri, le sottopagine grattacieli, gli header torri di guardia. https://daniele-michelin.com/it/blog/n8n-controllo-missione/ https://daniele-michelin.com/assets/og/n8n-controllo-missione.png Mission Control: un gioco n8n di risposta agli incidenti Gioca tre decisioni in 90 secondi su una vulnerabilità CISA realmente sfruttata. Scopri come ho costruito Mission Control e scarica il workflow n8n. https://daniele-michelin.com/it/blog/n8n-dna-del-sito/ https://daniele-michelin.com/assets/og/n8n-dna-del-sito.png DNA del sito: trovare codice di terzi con n8n Inserisci un dominio e guarda la doppia elica: codice proprio, terze parti, librerie con CVE note e cookie. Workflow n8n con OSV.dev e AI. https://daniele-michelin.com/it/blog/n8n-galassia-link/ https://daniele-michelin.com/assets/og/n8n-galassia-link.png Galassia dei link: i link interni in 3D Inserisci un dominio, ruota la galassia: link rotti come buchi neri, pagine orfane come pianeti. Workflow n8n con crawler, AI e download. https://daniele-michelin.com/it/blog/n8n-nextcloud-mattina-ufficio/ https://daniele-michelin.com/assets/og/n8n-nextcloud-mattina-ufficio.png Mattina in ufficio: n8n scrive in Nextcloud Un clic: n8n legge calendario, Deck, file e Talk di un ufficio demo in Nextcloud, un'AI scrive il briefing e n8n crea tutto davvero. https://daniele-michelin.com/it/blog/n8n-oracolo-dati/ https://daniele-michelin.com/assets/og/n8n-oracolo-dati.png Just for fun: un oracolo n8n fatto di dati live Un workflow n8n per gioco: tre fonti di dati live in parallelo, la fase lunare in un nodo Code, un'AI indovina e carte dei tarocchi da condividere. Con download. https://daniele-michelin.com/it/blog/n8n-orchestra-terra/ https://daniele-michelin.com/assets/og/n8n-orchestra-terra.png Orchestra Terra: terremoti e Sole diventano musica con n8n Orchestra Terra trasforma terremoti USGS e indice Kp NOAA in note e animazioni. Prova la demo, scopri le regole musicali e scarica il workflow n8n. https://daniele-michelin.com/it/blog/n8n-presentato-polso-di-internet/ https://daniele-michelin.com/assets/og/n8n-presentato-polso-di-internet.png n8n presentato: un workflow che misura il polso di Internet Cos'è n8n, perché lo ospito da me e un workflow d'esempio: 7 fonti, un'AI, una pagina live che si aggiorna con un clic. Con il file da scaricare e importare. https://daniele-michelin.com/it/blog/n8n-settimana-21-radar-aurore/ https://daniele-michelin.com/assets/og/n8n-settimana-21-radar-aurore.png n8n #21: radar aurore con indice Kp NOAA Leggi ogni 15 minuti l'indice Kp della NOAA e invia un push solo quando cresce l'attività geomagnetica. Senza chiave API né allarmi doppi. https://daniele-michelin.com/it/blog/n8n-talk-show-ai/ https://daniele-michelin.com/assets/og/n8n-talk-show-ai.png Il talk show AI: 5 AI parlano del tuo sito Hacker, guru SEO, designer, nonna Erna e un cliente impaziente parlano del tuo sito. Cinque AI in parallelo in n8n, con fallback e consigli. https://daniele-michelin.com/it/blog/nextcloud-collabora-code-falla-cve-2026-110447/ https://daniele-michelin.com/assets/og/nextcloud-collabora-code-falla-cve-2026-110447.png Nextcloud CODE, falla CVE-2026-110447: verifica, aggiorna, rimuovi CVE-2026-110447 permette di eseguire comandi sui server Nextcloud con l'app CODE di Collabora. Come verificare, aggiornare o rimuovere l'app e cercare web shell. https://daniele-michelin.com/it/blog/nextcloud-file-non-visibili-files-scan/ https://daniele-michelin.com/assets/og/nextcloud-file-non-visibili-files-scan.png Nextcloud non mostra i file copiati: occ files:scan File copiati direttamente nella cartella dati di Nextcloud ma l'interfaccia web resta vuota? Perché succede e come risolvere con occ files:scan. https://daniele-michelin.com/it/blog/nextcloud-saml-oidc-errori/ https://daniele-michelin.com/assets/og/nextcloud-saml-oidc-errori.png SSO Nextcloud non funziona? 8 errori SAML/OIDC risolti Loop di redirect, orologi sfasati, UID sbagliato, account doppi, gruppi mancanti: 8 errori SAML/OIDC dal supporto Nextcloud — con causa e soluzione. https://daniele-michelin.com/it/blog/nginx-vulnerabilita-ottobre-2026/ https://daniele-michelin.com/assets/og/nginx-vulnerabilita-ottobre-2026.png NGINX: tre falle critiche, aggiorna a 1.30.6 / 1.31.7 Correzione NGINX in 1.30.6 e 1.31.7 (Plus 37.1.0.1, 37.0.5.1): quali configurazioni sono colpite, come verificarle e aggiornare i container. https://daniele-michelin.com/it/blog/nota-operativa-linux-no-space-left/ https://daniele-michelin.com/assets/og/nota-operativa-linux-no-space-left.png Nota operativa: No space left on device con spazio libero: soluzione Nota operativa: No space left on device ma df mostra spazio libero? Di solito sono finiti gli inode o ci sono file cancellati ancora aperti. Diagnosi con… https://daniele-michelin.com/it/blog/nota-operativa-nextcloud-423-locked/ https://daniele-michelin.com/assets/og/nota-operativa-nextcloud-423-locked.png Nota operativa: Nextcloud "file is locked" (423 Locked): soluzione Nota operativa: Nextcloud dice is locked o 423 Locked? Lock dei file rimasti appesi. Come controllare il locking su Redis e il cron e togliere i lock… https://daniele-michelin.com/it/blog/pagella-sicurezza-sito/ https://daniele-michelin.com/assets/og/pagella-sicurezza-sito.png Una pagella per la sicurezza del tuo sito Inserisci un dominio e ricevi una pagella: voti per header di sicurezza, SPF/DMARC e certificato TLS, un voto finale e il giudizio del prof. Gratis. https://daniele-michelin.com/it/blog/php-aggiornamento-urgente-php2shell/ https://daniele-michelin.com/assets/og/php-aggiornamento-urgente-php2shell.png Patch PHP2Shell: Plesk, Synology, hosting e server Due falle critiche in PHP, corrette in 8.5.12, 8.4.27, 8.3.36 e 8.2.35: cosa fare su Plesk, Synology, hosting condiviso, Docker e server propri. https://daniele-michelin.com/it/blog/php2shell-soluzione-temporanea-php-ini/ https://daniele-michelin.com/assets/og/php2shell-soluzione-temporanea-php-ini.png PHP2Shell su Synology senza aggiornamento: php.ini Ancora nessun aggiornamento PHP su Synology? Tre impostazioni php.ini riducono la superficie d'attacco di PHP2Shell — per Web Station, Plesk e server. https://daniele-michelin.com/it/blog/php2shell-una-settimana-dopo-falla-kernel/ https://daniele-michelin.com/assets/og/php2shell-una-settimana-dopo-falla-kernel.png PHP2Shell dopo una settimana: attacchi e falla kernel PHP2Shell è sfruttata ed è nella lista CISA. Una falla del kernel Linux (CVE-2026-46300) la trasforma in root. I fatti nei grafici e cosa controllare oggi. https://daniele-michelin.com/it/blog/radar-truffe-avvisi-phishing-attuali/ https://daniele-michelin.com/assets/og/radar-truffe-avvisi-phishing-attuali.png Radar truffe: riconosci phishing e SMS falsi del momento Il mio nuovo radar truffe raccoglie le truffe del momento, le spiega in parole semplici e dice cosa fare. Come funziona e come riconoscere una truffa. https://daniele-michelin.com/it/cheat-sheet/comandi-dig/ https://daniele-michelin.com/assets/og/kb/it-c-dig.png Comandi dig – Cheat Sheet per il DNS · Daniele Michelin Comandi dig per la diagnosi DNS: A, MX, TXT, CAA, +short, +trace, reverse lookup, DNSSEC, verifica SPF/DKIM/DMARC e query ai nameserver autoritativi. https://daniele-michelin.com/it/cheat-sheet/comandi-docker/ https://daniele-michelin.com/assets/og/kb/it-c-docker.png Comandi Docker – Cheat Sheet per admin · Daniele Michelin I comandi Docker essenziali: immagini, container, log, exec, volumi, reti, Compose, pulizia con prune e limiti di risorse per admin. https://daniele-michelin.com/it/cheat-sheet/comandi-git/ https://daniele-michelin.com/assets/og/kb/it-c-git.png Comandi Git – Cheat Sheet per uso e recupero · Daniele Michelin I comandi Git essenziali: status, log, stash, rebase, recupero con reflog, varianti di undo, remote e bisect per l'uso quotidiano. https://daniele-michelin.com/it/cheat-sheet/comandi-journalctl/ https://daniele-michelin.com/assets/og/kb/it-c-journalctl.png Comandi journalctl – Cheat Sheet per Linux · Daniele Michelin Comandi journalctl per il troubleshooting: filtra i log per unit, boot, orario e priorità, seguili live, output JSON e limita lo spazio del journal. https://daniele-michelin.com/it/cheat-sheet/comandi-nginx/ https://daniele-michelin.com/assets/og/kb/it-c-nginx.png Comandi nginx – Cheat Sheet per admin · Daniele Michelin I comandi nginx essenziali per admin: test e reload, log, redirect, proxy_pass, rate limiting, gzip e debug in produzione. https://daniele-michelin.com/it/cheat-sheet/comandi-occ-nextcloud/ https://daniele-michelin.com/assets/og/kb/it-c-occ.png Comandi occ di Nextcloud – Cheat Sheet per admin · Daniele Michelin I comandi occ di Nextcloud essenziali per admin: modalità manutenzione, files:scan, utenti, app, indici DB mancanti, cron, cestino e 2FA. https://daniele-michelin.com/it/cheat-sheet/comandi-openssl/ https://daniele-michelin.com/assets/og/kb/it-c-openssl.png Comandi OpenSSL – Cheat Sheet TLS e certificati · Daniele Michelin Comandi OpenSSL per la diagnosi TLS: verifica catena e scadenza, crea una CSR, confronta chiave e certificato, converti PEM/DER/PFX, testa STARTTLS. https://daniele-michelin.com/it/cheat-sheet/comandi-systemctl/ https://daniele-michelin.com/assets/og/kb/it-c-systemctl.png Comandi systemctl – Cheat Sheet systemd · Daniele Michelin I comandi systemctl essenziali: stato, start, restart, enable, timer, override drop-in, systemd-analyze e target per admin Linux. https://daniele-michelin.com/it/cheat-sheet/ https://daniele-michelin.com/assets/og/kb/it-hub-cheats.png Cheat sheet per admin: nginx, Docker, Git, systemd e altri Riferimenti di comandi consultabili per Nextcloud occ, dig, journalctl, openssl, nginx, systemctl, Docker e Git — con pulsante copia e avvisi sui comandi rischiosi. https://daniele-michelin.com/it/confronto/differenza-spf-dkim-dmarc/ https://daniele-michelin.com/assets/og/kb/it-v-spf-dkim-dmarc.png SPF vs DKIM vs DMARC: tabella di confronto · Daniele Michelin Cosa controllano SPF, DKIM e DMARC, dove falliscono e perché ti servono tutti e tre. Con allineamento, inoltri ed errori tipici visti sul campo. https://daniele-michelin.com/it/confronto/http-01-vs-dns-01/ https://daniele-michelin.com/assets/og/kb/it-v-http-01-vs-dns-01.png Let's Encrypt: challenge HTTP-01 o DNS-01 · Daniele Michelin Challenge HTTP-01 o DNS-01 per Let's Encrypt? Wildcard, host interni, porta 80, accesso API al DNS ed errori tipici di validazione a confronto. https://daniele-michelin.com/it/confronto/ https://daniele-michelin.com/assets/og/kb/it-hub-compare.png Confronti tecnici per admin: SAML, Nextcloud, DNS · Daniele Michelin Confronti onesti dal lavoro quotidiano: SAML o OIDC, Nextcloud o Seafile, HTTP-01 o DNS-01, cron o timer systemd — quando scegliere cosa. https://daniele-michelin.com/it/confronto/nextcloud-aio-vs-installazione-manuale/ https://daniele-michelin.com/assets/og/kb/it-v-nextcloud-aio-vs-manual.png Nextcloud AIO vs installazione manuale · Daniele Michelin Nextcloud All-in-One o setup classico con web server, PHP-FPM e database? Impegno, controllo, aggiornamenti, backup e debug confrontati con onestà. https://daniele-michelin.com/it/confronto/nextcloud-s3-vs-nfs/ https://daniele-michelin.com/assets/og/kb/it-v-s3-vs-nfs-nextcloud.png Nextcloud: S3 vs NFS come storage primario · Daniele Michelin Object storage S3 o NFS/block storage come storage primario di Nextcloud? Formato dei dati, scalabilità, backup, migrazione e trappole viste in produzione. https://daniele-michelin.com/it/confronto/nextcloud-vs-seafile/ https://daniele-michelin.com/assets/og/kb/it-v-nextcloud-vs-seafile.png Nextcloud vs Seafile: confronto · Daniele Michelin Nextcloud o Seafile in self-hosting? Formato di archiviazione, sync, funzioni, aggiornamenti e backup a confronto, dal punto di vista di chi lo gestisce. https://daniele-michelin.com/it/confronto/nginx-vs-apache-php-fpm/ https://daniele-michelin.com/assets/og/kb/it-v-nginx-vs-apache-php.png nginx vs Apache per app PHP · Daniele Michelin nginx o Apache davanti a PHP-FPM? .htaccess, configurazione, limiti di upload, timeout e debug per Nextcloud, WordPress e altre app PHP a confronto. https://daniele-michelin.com/it/confronto/saml-vs-oidc/ https://daniele-michelin.com/assets/og/kb/it-v-saml-vs-oidc.png SAML vs OIDC: quale scegliere e quando · Daniele Michelin SAML o OpenID Connect per il single sign-on? Differenze su protocollo, client, certificati e debug, dall'esperienza con Nextcloud e Keycloak. https://daniele-michelin.com/it/confronto/systemd-timer-vs-cron/ https://daniele-michelin.com/assets/og/kb/it-v-systemd-timer-vs-cron.png Timer systemd vs cron: confronto · Daniele Michelin Timer systemd o cron per i job pianificati? Log, esecuzioni perse, sovrapposizioni, ambiente e impegno a confronto, con esempi dal lavoro quotidiano. https://daniele-michelin.com/it/demo/opscope/ https://daniele-michelin.com/assets/og/projects/opscope-demo-it.png OPSCOPE demo live: diagnostica server Linux · Daniele Michelin Registrazione di OPSCOPE, il mio toolkit Bash in sola lettura per server Linux: un incidente simulato dalla diagnosi al report. https://daniele-michelin.com/it/errori/apt-could-not-get-lock-dpkg-lock-frontend/ https://daniele-michelin.com/assets/og/kb/it-e-apt-dpkg-lock.png apt: errore lock dpkg lock-frontend, soluzione · Daniele Michelin apt segnala Could not get lock /var/lib/dpkg/lock-frontend. Di solito è in corso unattended-upgrades. Come aspettare e ripristinare in sicurezza. https://daniele-michelin.com/it/errori/apt-e-unable-to-locate-package/ https://daniele-michelin.com/assets/og/kb/it-e-apt-unable-to-locate-package.png apt: E: Unable to locate package – soluzione · Daniele Michelin apt install si ferma con E: Unable to locate package. Liste pacchetti vecchie, nome errato, componente mancante o release a fine vita. Controlli e soluzioni. https://daniele-michelin.com/it/errori/apt-nopubkey-signature/ https://daniele-michelin.com/assets/og/kb/it-e-apt-nopubkey-signature.png apt: NO_PUBKEY – firma non verificabile · Daniele Michelin apt segnala NO_PUBKEY quando manca o è scaduta la chiave di firma di un repository. Ecco come recuperare la chiave giusta senza ignorare l'avviso. https://daniele-michelin.com/it/errori/bash-argument-list-too-long/ https://daniele-michelin.com/assets/og/kb/it-e-bash-argument-list-too-long.png bash: Argument list too long (rm, cp, mv) – soluzione rm, cp o mv falliscono con Argument list too long. La shell ha espanso * in più file di quanti il kernel ne consenta. Usa find con -delete o -exec, o xargs. https://daniele-michelin.com/it/errori/cambiare-canale-wifi-2-4-5-ghz/ https://daniele-michelin.com/assets/og/kb/it-e-wlan-kanal-wechseln.png Cambiare canale Wi-Fi: scegliere 2,4 o 5 GHz · Daniele Michelin Quale banda e quale canale Wi-Fi scegliere? Spiega 2,4 e 5 GHz, canali 1, 6, 11, controllo delle reti vicine con comandi reali e cambio nel router. https://daniele-michelin.com/it/errori/cambiare-server-dns/ https://daniele-michelin.com/assets/og/kb/it-e-dns-server-wechseln.png Cambiare server DNS sul router o sul PC · Daniele Michelin Le pagine non si aprono ma ping 8.8.8.8 funziona? Indica un problema DNS. Testa con nslookup e cambia il server DNS, con un avviso sulla privacy. https://daniele-michelin.com/it/errori/certbot-failed-to-renew-certificate-renewals-failed/ https://daniele-michelin.com/assets/og/kb/it-e-certbot-failed-to-renew-certificate.png certbot: rinnovo del certificato non riuscito · Daniele Michelin certbot renew stampa Failed to renew certificate e il certificato scade. Authenticator cambiato, porta 80 occupata, timer assente o hook rotto. Dry-run e soluzione. https://daniele-michelin.com/it/errori/certbot-timeout-during-connect-firewall/ https://daniele-michelin.com/assets/og/kb/it-e-certbot-timeout-during-connect.png Certbot: timeout during connect, firewall · Daniele Michelin Let's Encrypt fallisce con Timeout during connect (likely firewall problem). Porta 80 bloccata, IP errato o IPv6 non raggiungibile. Controlli e soluzione. https://daniele-michelin.com/it/errori/configurare-rete-ospiti-wifi/ https://daniele-michelin.com/assets/og/kb/it-e-gastnetz-einrichten.png Rete ospiti Wi-Fi: come configurarla e perché · Daniele Michelin A cosa serve il Wi-Fi ospiti, come attivarlo nel router e perché stampante, TV e NAS non si vedono da lì. Con comandi di verifica. https://daniele-michelin.com/it/errori/cron-job-non-parte/ https://daniele-michelin.com/assets/og/kb/it-e-cron-job-laeuft-nicht.png Cronjob non parte: cause e verifiche · Daniele Michelin Un cronjob non parte anche se è in crontab: di solito è colpa di PATH, ambiente, permessi o un errore di sintassi. Ecco come trovarlo in pochi minuti. https://daniele-michelin.com/it/errori/curl-6-could-not-resolve-host/ https://daniele-michelin.com/assets/og/kb/it-e-curl-6-could-not-resolve-host.png curl: (6) Could not resolve host – soluzione · Daniele Michelin curl fallisce con (6) Could not resolve host. Nessun record DNS, un refuso, un problema del resolver o cache vecchia. Chiarisci con dig e getent prima di cambiare. https://daniele-michelin.com/it/errori/dig-connection-timed-out-no-servers-could-be-reached/ https://daniele-michelin.com/assets/og/kb/it-e-dns-no-servers-could-be-reached.png dig: no servers could be reached (timeout) · Daniele Michelin dig o nslookup stampano connection timed out; no servers could be reached. Server DNS spento, irraggiungibile o porta 53 filtrata. Trova il tratto che fallisce. https://daniele-michelin.com/it/errori/dkim-fail-body-hash-did-not-verify/ https://daniele-michelin.com/assets/og/kb/it-e-dkim-body-hash-did-not-verify.png DKIM: body hash did not verify – soluzione · Daniele Michelin dkim=fail (body hash did not verify): il corpo è cambiato dopo la firma. Trova footer, filtro o gateway che modifica la posta e firma per ultimo. https://daniele-michelin.com/it/errori/dmarc-unauthenticated-email-not-accepted-dmarc-policy/ https://daniele-michelin.com/assets/og/kb/it-e-dmarc-policy-rejected.png DMARC: email rifiutata per policy DMARC · Daniele Michelin 550 5.7.1 Unauthenticated email is not accepted due to DMARC policy. Allinea SPF e DKIM, controlla gli inoltri e porta p=reject in sicurezza. https://daniele-michelin.com/it/errori/dns-cname-at-zone-apex-not-allowed/ https://daniele-michelin.com/assets/og/kb/it-e-dns-cname-apex.png DNS: CNAME sull'apex non consentito, soluzione · Daniele Michelin Errore “CNAME and other data” o “CNAME at apex not allowed”: il dominio principale non può avere un CNAME. Perché, e quali alternative funzionano davvero. https://daniele-michelin.com/it/errori/dns-nxdomain-dns-probe-finished-nxdomain/ https://daniele-michelin.com/assets/og/kb/it-e-dns-nxdomain.png DNS NXDOMAIN / DNS_PROBE_FINISHED_NXDOMAIN: fix · Daniele Michelin NXDOMAIN o DNS_PROBE_FINISHED_NXDOMAIN significa che per il DNS il nome non esiste. Trova refuso, record mancante, delega errata o cache negativa. https://daniele-michelin.com/it/errori/dns-servfail-dnssec/ https://daniele-michelin.com/assets/og/kb/it-e-dns-servfail.png DNS SERVFAIL: trovare la causa (DNSSEC e altro) · Daniele Michelin dig restituisce SERVFAIL anche se la zona sembra giusta? Spesso è DNSSEC rotto, ad es. un DS vecchio dopo il cambio provider. Come trovarlo e risolvere. https://daniele-michelin.com/it/errori/dns-status-refused-query-refused/ https://daniele-michelin.com/assets/og/kb/it-e-dns-query-refused.png DNS: status REFUSED – cause e soluzione · Daniele Michelin dig mostra status: REFUSED. Un name server non risponde: la zona non è lì, la ricorsione non è consentita a te o una ACL ti blocca. Controlli e soluzioni. https://daniele-michelin.com/it/errori/docker-permission-denied-docker-sock/ https://daniele-michelin.com/assets/og/kb/it-e-docker-sock-permission-denied.png Docker: permission denied su docker.sock · Daniele Michelin Docker segnala permission denied nel connettersi al socket del demone. Aggiungi l'utente al gruppo docker, riaccedi e conosci il costo in sicurezza. https://daniele-michelin.com/it/errori/docker-port-already-allocated/ https://daniele-michelin.com/assets/og/kb/it-e-docker-port-already-allocated.png Docker: porta già allocata (Bind failed) · Daniele Michelin “port is already allocated” significa che un altro container o un processo dell'host occupa la porta. Ecco come trovare il proprietario e risolvere. https://daniele-michelin.com/it/errori/dovecot-imap-login-disconnected-auth-failed/ https://daniele-michelin.com/assets/og/kb/it-e-dovecot-auth-failed.png Dovecot: Disconnected (auth failed), soluzione · Daniele Michelin Dovecot scrive “imap-login: Disconnected (auth failed)”? Come distinguere password errata, errore di configurazione e brute force e risolvere la causa. https://daniele-michelin.com/it/errori/dovecot-mailbox-open-failed-permission-denied/ https://daniele-michelin.com/assets/og/kb/it-e-dovecot-mailbox-permission-denied.png Dovecot: permission denied sulla casella · Daniele Michelin Dovecot registra open() failed: Permission denied su casella o Maildir. Proprietario o mail_location errati dopo una migrazione. Soluzioni. https://daniele-michelin.com/it/errori/dpkg-was-interrupted-configure-a/ https://daniele-michelin.com/assets/og/kb/it-e-dpkg-was-interrupted.png dpkg was interrupted: configure -a – soluzione · Daniele Michelin apt si ferma con “dpkg was interrupted, you must manually run dpkg --configure -a”. Un aggiornamento interrotto o uno script fallito. Controlli e riparazione sicura. https://daniele-michelin.com/it/errori/due-router-doppio-nat/ https://daniele-michelin.com/assets/og/kb/it-e-mehrere-router-doppel-nat.png Due router in casa: il doppio NAT spiegato · Daniele Michelin Due router in cascata causano il doppio NAT e il port forwarding o le connessioni di gioco falliscono. Come riconoscere e risolvere il problema. https://daniele-michelin.com/it/errori/err-too-many-redirects-redirect-loop/ https://daniele-michelin.com/assets/og/kb/it-e-http-too-many-redirects.png ERR_TOO_MANY_REDIRECTS: troppi reindirizzamenti · Daniele Michelin Il browser mostra ERR_TOO_MANY_REDIRECTS: ti ha reindirizzato troppe volte. Loop tra http e https, www, CDN o applicazione. Come trovarlo e interromperlo. https://daniele-michelin.com/it/errori/fritzbox-niente-internet/ https://daniele-michelin.com/assets/og/kb/it-e-fritzbox-internet-weg.png FRITZ!Box senza internet: controllo in 5 passi · Daniele Michelin Niente internet sulla FRITZ!Box? Controlla spie, riavvio, cavi e DNS in cinque passi e scopri quando conviene chiamare il provider. https://daniele-michelin.com/it/errori/fritzbox-non-raggiungibile/ https://daniele-michelin.com/assets/og/kb/it-e-fritzbox-nicht-erreichbar.png fritz.box non si apre: cause e soluzione · Daniele Michelin fritz.box non si apre? Controlla connessione, indirizzo 192.168.178.1, DNS e browser passo dopo passo con comandi semplici e trova la causa. https://daniele-michelin.com/it/errori/fritzbox-password-dimenticata/ https://daniele-michelin.com/assets/og/kb/it-e-fritzbox-passwort-vergessen.png Password FRITZ!Box dimenticata: come rientrare · Daniele Michelin Hai dimenticato la password della FRITZ!Box? Trova quella standard sull'etichetta, controlla che sia raggiungibile e rientra nelle impostazioni. Passi semplici. https://daniele-michelin.com/it/errori/fritzbox-password-wifi-trovare-cambiare/ https://daniele-michelin.com/assets/og/kb/it-e-fritzbox-wlan-passwort.png Password Wi-Fi FRITZ!Box: trovarla o cambiarla · Daniele Michelin Password Wi-Fi della FRITZ!Box dimenticata? Trovala sull'etichetta, nell'interfaccia o sul computer e cambiala in sicurezza. Con indicazioni sui menu. https://daniele-michelin.com/it/errori/fritzbox-ripristino-di-fabbrica/ https://daniele-michelin.com/assets/og/kb/it-e-fritzbox-werkseinstellungen.png Ripristino FRITZ!Box: cosa si perde davvero · Daniele Michelin Ripristino della FRITZ!Box alle impostazioni di fabbrica: quando serve, cosa si perde e come salvare prima un backup delle impostazioni. Per chi usa la rete a casa. https://daniele-michelin.com/it/errori/http-400-request-header-or-cookie-too-large/ https://daniele-michelin.com/assets/og/kb/it-e-http-400-header-too-large.png 400 Request Header Or Cookie Too Large: soluzione · Daniele Michelin nginx risponde 400 “Request Header Or Cookie Too Large”: cookie o token troppi o troppo grandi. Cause, test con curl e dimensioni sicure dei buffer. https://daniele-michelin.com/it/errori/http-403-forbidden-nginx/ https://daniele-michelin.com/assets/og/kb/it-e-http-403.png HTTP 403 Forbidden su nginx: cause e soluzione · Daniele Michelin HTTP 403 Forbidden su nginx: file index mancante, permessi, regole deny o SELinux. Come trovare la causa esatta nell'error.log e risolverla. https://daniele-michelin.com/it/errori/http-404-not-found-nginx/ https://daniele-michelin.com/assets/og/kb/it-e-http-404-nginx.png nginx: 404 Not Found su pagine esistenti · Daniele Michelin nginx restituisce 404 Not Found anche se la pagina dovrebbe esistere. root o alias errato, try_files mancante, server block sbagliato. Controlli e fix. https://daniele-michelin.com/it/errori/http-413-request-entity-too-large/ https://daniele-michelin.com/assets/og/kb/it-e-http-413.png HTTP 413 Request Entity Too Large: fix per nginx · Daniele Michelin 413 Request Entity Too Large: nginx o un proxy a monte blocca gli upload grandi. Come impostare bene client_max_body_size e i limiti PHP. https://daniele-michelin.com/it/errori/http-429-too-many-requests/ https://daniele-michelin.com/assets/og/kb/it-e-http-429.png HTTP 429 Too Many Requests: cause e soluzione · Daniele Michelin HTTP 429 Too Many Requests significa che è scattato un rate limit. Trova quale livello ti limita (nginx, WAF, CDN, API) e regola o rispetta il limite. https://daniele-michelin.com/it/errori/http-500-internal-server-error-php/ https://daniele-michelin.com/assets/og/kb/it-e-http-500.png HTTP 500 Internal Server Error: trovare la causa · Daniele Michelin HTTP 500 Internal Server Error è solo il sintomo. Come trovare la causa nei log di nginx e PHP: fatal error, limite di memoria, permessi, loop di rewrite. https://daniele-michelin.com/it/errori/http-502-bad-gateway/ https://daniele-michelin.com/assets/og/kb/it-e-http-502.png HTTP 502 Bad Gateway (nginx, PHP-FPM): soluzione · Daniele Michelin 502 Bad Gateway su nginx: il backend (PHP-FPM, Node, Gunicorn) non risponde. Cause tipiche, cosa cercare nell'error.log e soluzioni rapide. https://daniele-michelin.com/it/errori/http-503-service-unavailable-nginx/ https://daniele-michelin.com/assets/og/kb/it-e-http-503.png HTTP 503 Service Unavailable: cause e soluzione · Daniele Michelin HTTP 503 Service Unavailable con nginx: rate limit, maintenance mode, backend sovraccarico o load balancer senza server sani. Come trovare la fonte. https://daniele-michelin.com/it/errori/http-504-gateway-timeout/ https://daniele-michelin.com/assets/og/kb/it-e-http-504.png HTTP 504 Gateway Timeout (nginx): cause e soluzione · Daniele Michelin 504 Gateway Timeout su nginx: il backend ci mette troppo. Come trovare script lenti, pool PHP-FPM saturo e timeout sbagliati, e come risolvere. https://daniele-michelin.com/it/errori/http-521-522-origin-error-cdn/ https://daniele-michelin.com/assets/og/kb/it-e-http-521-522-origin.png HTTP 521 / 522: il CDN non raggiunge l'origin · Daniele Michelin Una pagina del CDN mostra 521 Web server is down o 522 Connection timed out. L'edge non raggiunge il tuo origin: firewall, IP errato, servizio fermo. Fix. https://daniele-michelin.com/it/errori/ https://daniele-michelin.com/assets/og/kb/it-hub-errors.png Lessico dei codici d'errore: SMTP, HTTP, Nextcloud · Daniele Michelin Messaggi d'errore frequenti di mail, web server, Nextcloud, DNS e SSO: cosa significano, come verificarli e come risolverli — con i comandi. https://daniele-michelin.com/it/errori/letsencrypt-acme-error-unauthorized/ https://daniele-michelin.com/assets/og/kb/it-e-acme-unauthorized.png Let's Encrypt acme:error:unauthorized: soluzione · Daniele Michelin certbot dà urn:ietf:params:acme:error:unauthorized? La challenge HTTP-01 fallisce, spesso per un record AAAA o un redirect. Diagnosi e soluzione. https://daniele-michelin.com/it/errori/letsencrypt-too-many-certificates-already-issued/ https://daniele-michelin.com/assets/og/kb/it-e-letsencrypt-too-many-certificates.png Let's Encrypt too many certificates: limite · Daniele Michelin Let's Encrypt dice “too many certificates already issued”? Quale rate limit scatta, come attendere lo sblocco e come evitare in futuro i loop di emissione. https://daniele-michelin.com/it/errori/linux-no-space-left-on-device/ https://daniele-michelin.com/assets/og/kb/it-e-linux-no-space-left.png No space left on device con spazio libero: soluzione No space left on device ma df mostra spazio libero? Di solito sono finiti gli inode o ci sono file cancellati ancora aperti. Diagnosi con df -i e lsof +L1. https://daniele-michelin.com/it/errori/linux-out-of-memory-killed-process-oom-killer/ https://daniele-michelin.com/assets/og/kb/it-e-linux-oom-killer.png Linux OOM killer: out of memory, processo ucciso · Daniele Michelin “Out of memory: Killed process” nel log del kernel: l'OOM killer ha terminato un processo. Trova il colpevole, limita la memoria ed evita che si ripeta. https://daniele-michelin.com/it/errori/linux-read-only-file-system/ https://daniele-michelin.com/assets/og/kb/it-e-linux-read-only-file-system.png Linux: read-only file system, cause e soluzione · Daniele Michelin “Read-only file system” su Linux: errori del filesystem con remount-ro, disco guasto, mount ro o ProtectSystem di systemd. Diagnosi sicura e soluzione. https://daniele-michelin.com/it/errori/linux-too-many-open-files/ https://daniele-michelin.com/assets/og/kb/it-e-linux-too-many-open-files.png Linux: too many open files (EMFILE), soluzione · Daniele Michelin “Too many open files” (errore 24) in nginx, Java o Node: raggiunto il limite per processo. Verifica corretta, LimitNOFILE in systemd e ricerca dei leak. https://daniele-michelin.com/it/errori/mariadb-table-is-marked-as-crashed-and-should-be-repaired/ https://daniele-michelin.com/assets/og/kb/it-e-mariadb-table-marked-as-crashed.png MariaDB: Table is marked as crashed – soluzione · Daniele Michelin MariaDB o MySQL segnala Table is marked as crashed and should be repaired (errore 1194 o 145). Di solito MyISAM o Aria dopo un crash. Prima backup, poi REPAIR TABLE. https://daniele-michelin.com/it/errori/mixed-content-blocked-insecure-resource/ https://daniele-michelin.com/assets/og/kb/it-e-http-mixed-content.png Mixed Content: risorsa non sicura bloccata · Daniele Michelin La console del browser segnala Mixed Content: pagina caricata in HTTPS ma richiesta una risorsa non sicura, e la blocca. Trova gli URL http:// e correggili. https://daniele-michelin.com/it/errori/mount-wrong-fs-type-bad-option-bad-superblock/ https://daniele-michelin.com/assets/og/kb/it-e-mount-wrong-fs-type-bad-superblock.png mount: wrong fs type, bad superblock – soluzione · Daniele Michelin mount fallisce con wrong fs type, bad option, bad superblock. Helper mancante, tipo errato, nessun filesystem o danno. Prima controlli sicuri, poi si interviene. https://daniele-michelin.com/it/errori/mysql-1045-access-denied/ https://daniele-michelin.com/assets/og/kb/it-e-mysql-1045-access-denied.png MySQL errore 1045: Access denied for user · Daniele Michelin MySQL / MariaDB ERROR 1045 Access denied for user. Password errata, host sbagliato o plugin unix_socket di root. Controlli e soluzione in pochi minuti. https://daniele-michelin.com/it/errori/mysql-1064-syntax-error/ https://daniele-michelin.com/assets/og/kb/it-e-mysql-1064-syntax-error.png MariaDB/MySQL: errore 1064 di sintassi · Daniele Michelin L'errore 1064 significa che il server non riesce a interpretare la query. Di solito è una parola riservata, una differenza di versione o un apice. https://daniele-michelin.com/it/errori/mysql-1067-invalid-default-value/ https://daniele-michelin.com/assets/og/kb/it-e-mysql-1067-invalid-default-value.png MySQL: errore 1067 Invalid default value · Daniele Michelin L'errore 1067 indica che il valore di default di una colonna non è valido per il tipo o per il sql_mode attivo. Tipico con TIMESTAMP. https://daniele-michelin.com/it/errori/mysql-2003-cant-connect-10061/ https://daniele-michelin.com/assets/og/kb/it-e-mysql-2003-cant-connect-10061.png MySQL: ERROR 2003 Can't connect (10061) · Daniele Michelin L'errore 2003 (HY000) con 10061 significa che sulla porta di destinazione nessuno accetta connessioni. Spesso il servizio è fermo o ascolta solo in locale. https://daniele-michelin.com/it/errori/mysql-error-1040-too-many-connections/ https://daniele-michelin.com/assets/og/kb/it-e-mysql-1040-too-many-connections.png MySQL: ERROR 1040 Too many connections – soluzione · Daniele Michelin MySQL o MariaDB rifiuta nuovi client con ERROR 1040 Too many connections. Trova app che perdono connessioni e query lente prima di alzare max_connections. https://daniele-michelin.com/it/errori/mysql-error-2002-cant-connect-through-socket/ https://daniele-michelin.com/assets/og/kb/it-e-mysql-2002-socket.png MySQL errore 2002: connessione tramite socket · Daniele Michelin MySQL / MariaDB ERROR 2002: Can't connect to local server through socket. Server fermo, percorso del socket errato o disco pieno. Controlli e soluzioni. https://daniele-michelin.com/it/errori/mysql-server-has-gone-away-2006/ https://daniele-michelin.com/assets/og/kb/it-e-mysql-2006-server-has-gone-away.png MySQL server has gone away (errore 2006) · Daniele Michelin MySQL o MariaDB segnala MySQL server has gone away, errore 2006. Timeout di inattività, pacchetto oltre max_allowed_packet o crash del server. Controlli e soluzioni. https://daniele-michelin.com/it/errori/net-err-cert-authority-invalid-self-signed/ https://daniele-michelin.com/assets/og/kb/it-e-tls-cert-authority-invalid.png ERR_CERT_AUTHORITY_INVALID: autofirmato · Daniele Michelin Il browser mostra NET::ERR_CERT_AUTHORITY_INVALID: certificato autofirmato, di una CA interna non attendibile o servito senza catena. Come verificare e risolvere. https://daniele-michelin.com/it/errori/net-err-cert-common-name-invalid/ https://daniele-michelin.com/assets/og/kb/it-e-tls-cert-common-name-invalid.png ERR_CERT_COMMON_NAME_INVALID: cause e soluzione · Daniele Michelin Chrome mostra NET::ERR_CERT_COMMON_NAME_INVALID: il nome host non è nel certificato. Controlla i SAN, trova il vhost sbagliato ed estendi il certificato. https://daniele-michelin.com/it/errori/net-err-cert-date-invalid-clock-wrong/ https://daniele-michelin.com/assets/og/kb/it-e-tls-cert-date-invalid.png ERR_CERT_DATE_INVALID: orologio o validità · Daniele Michelin NET::ERR_CERT_DATE_INVALID: certificato scaduto o non ancora valido per l'orologio in uso. Spesso l'orologio del dispositivo è sbagliato. Confronta le date. https://daniele-michelin.com/it/errori/nextcloud-cannot-write-into-config-directory/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-config-not-writable.png Nextcloud: impossibile scrivere in config · Daniele Michelin Nextcloud segnala Cannot write into config directory. Proprietario errato dopo un ripristino, SELinux o config_is_read_only. Controlli e permessi. https://daniele-michelin.com/it/errori/nextcloud-csrf-check-failed/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-csrf-check-failed.png Nextcloud “CSRF check failed”: soluzione · Daniele Michelin Nextcloud dice “CSRF check failed” al login o al salvataggio? Di solito la sessione si perde: controlla cookie, proxy, sessioni e Redis. https://daniele-michelin.com/it/errori/nextcloud-data-directory-readable-by-other-users/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-data-dir-readable.png Nextcloud: data directory leggibile da altri · Daniele Michelin Nextcloud dice “Your data directory is readable by other users”. Come impostare 0770 nel modo giusto, anche su mount NFS e CIFS, senza rompere l'accesso. https://daniele-michelin.com/it/errori/nextcloud-database-is-missing-some-indexes/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-missing-indexes.png Nextcloud: mancano indici nel database, soluzione · Daniele Michelin Nextcloud dice “The database is missing some indexes”. Come aggiungere con occ indici, colonne e chiavi primarie in sicurezza. https://daniele-michelin.com/it/errori/nextcloud-file-is-locked-423/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-423-locked.png Nextcloud "file is locked" (423 Locked): soluzione · Daniele Michelin Nextcloud dice is locked o 423 Locked? Lock dei file rimasti appesi. Come controllare il locking su Redis e il cron e togliere i lock vecchi senza rischi. https://daniele-michelin.com/it/errori/nextcloud-internal-server-error-request-id/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-internal-server-error.png Nextcloud Internal Server Error: trovare la causa · Daniele Michelin Nextcloud mostra “Internal Server Error” con un Request ID? Come trovare la voce corrispondente in nextcloud.log e risolvere le cause più comuni. https://daniele-michelin.com/it/errori/nextcloud-last-background-job-ran-ago-cron/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-cron-last-job.png Nextcloud: last background job fermo, soluzione · Daniele Michelin Nextcloud dice “Last background job execution ran … ago”? Controlla modalità cron, crontab di www-data ed errori di cron.php e risolvi in modo stabile. https://daniele-michelin.com/it/errori/nextcloud-maintenance-mode-enabled/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-maintenance-mode.png Nextcloud bloccato in maintenance mode: soluzione · Daniele Michelin Nextcloud resta in maintenance mode, di solito dopo un aggiornamento interrotto? Come controllare lo stato con occ, chiudere l'upgrade e disattivarla. https://daniele-michelin.com/it/errori/nextcloud-memcache-apcu-not-available-for-local-cache/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-memcache-apcu.png Nextcloud: memcache APCu not available, soluzione · Daniele Michelin Nextcloud mostra “Memcache APCu not available for local cache” con occ o cron: di solito manca apc.enable_cli=1 nel php.ini della CLI. Verifica e fix. https://daniele-michelin.com/it/errori/nextcloud-redisexception-redis-went-away/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-redis-went-away.png Nextcloud: Redis went away – cause e soluzione · Daniele Michelin Nextcloud registra RedisException: Redis went away e le pagine si bloccano o danno 500. Redis fermo, socket o permessi errati, o RAM esaurita. Controlli e soluzione. https://daniele-michelin.com/it/errori/nextcloud-reverse-proxy-header-configuration-incorrect/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-reverse-proxy-header.png Nextcloud: header del reverse proxy errati · Daniele Michelin Nextcloud segnala che la configurazione degli header del reverse proxy è errata. Come impostare trusted_proxies e gli header dietro nginx, Traefik o Cloudflare. https://daniele-michelin.com/it/errori/nextcloud-saml-signature-validation-failed/ https://daniele-michelin.com/assets/og/kb/it-e-saml-signature-validation-failed.png SAML in Nextcloud: errore di validazione della firma Nextcloud user_saml dice Signature validation failed. SAML Response rejected? Di solito è il certificato dell'IdP rinnovato. Cause, verifiche e soluzione. https://daniele-michelin.com/it/errori/nextcloud-some-files-have-not-passed-the-integrity-check/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-integrity-check-failed.png Nextcloud: controllo di integrità non superato · Daniele Michelin Nextcloud elenca INVALID_HASH, MISSING_FILE o EXTRA_FILE dopo il controllo di integrità. Residui di un aggiornamento manuale o file modificati. Come risolvere. https://daniele-michelin.com/it/errori/nextcloud-too-many-requests-brute-force-protection/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-too-many-requests.png Nextcloud: too many requests, protezione brute force Nextcloud mostra Too many requests from your network. La protezione brute force rallenta un IP. Come azzerarla e risolvere l'IP condiviso del proxy. https://daniele-michelin.com/it/errori/nextcloud-trusted-domain-error/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-trusted-domain.png Nextcloud "access through untrusted domain": soluzione Nextcloud dice access through untrusted domain: il nome host manca in trusted_domains. Come aggiungerlo con occ e controllare il reverse proxy. https://daniele-michelin.com/it/errori/nextcloud-updates-between-multiple-major-versions-unsupported/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-multiple-major-versions-unsupported.png Nextcloud: aggiornamento tra major bloccato · Daniele Michelin occ upgrade o l'updater si ferma: aggiornamenti tra più major e downgrade non supportati. Aggiorna una major alla volta o allinea codice e database. Soluzione. https://daniele-michelin.com/it/errori/nextcloud-well-known-caldav-carddav-not-set-up/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-well-known-caldav-carddav.png Nextcloud: /.well-known/caldav non configurato · Daniele Michelin Nextcloud avvisa che il web server non risolve /.well-known/caldav o carddav. Aggiungi i redirect 301 verso /remote.php/dav in nginx o Apache. Controlli e soluzione. https://daniele-michelin.com/it/errori/nextcloud-your-data-directory-is-invalid-ocdata/ https://daniele-michelin.com/assets/og/kb/it-e-nextcloud-data-directory-invalid.png Nextcloud: data directory non valida – soluzione · Daniele Michelin Nextcloud dice che la data directory non è valida e chiede .ocdata. Volume non montato, percorso errato in config.php o file perso. Controlli e soluzione. https://daniele-michelin.com/it/errori/nginx-bind-address-already-in-use/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-address-in-use.png nginx bind() fallito (98): indirizzo già in uso · Daniele Michelin nginx non parte: bind() to 0.0.0.0:80 failed (98: Address already in use). Come trovare il processo che occupa la porta e risolvere in un minuto. https://daniele-michelin.com/it/errori/nginx-connect-failed-111-connection-refused-upstream/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-connection-refused-111.png nginx: connect() failed (111), soluzione · Daniele Michelin nginx scrive “connect() failed (111: Connection refused) while connecting to upstream”: il backend è giù o ascolta altrove. Verifica e soluzione. https://daniele-michelin.com/it/errori/nginx-could-not-build-server-names-hash/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-server-names-hash.png nginx: could not build server_names_hash – soluzione nginx -t fallisce con could not build server_names_hash, you should increase server_names_hash_bucket_size. Perché succede e quale impostazione modificare. https://daniele-michelin.com/it/errori/nginx-emerg-cannot-load-certificate-pem-no-start-line/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-cannot-load-certificate.png nginx: [emerg] cannot load certificate – soluzione · Daniele Michelin nginx -t fallisce con cannot load certificate, no start line o key values mismatch. Percorso o file errato o chiave non corrispondente. Controlli e fix. https://daniele-michelin.com/it/errori/nginx-php-fpm-primary-script-unknown-file-not-found/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-primary-script-unknown.png nginx PHP-FPM: Primary script unknown, soluzione · Daniele Michelin nginx mostra “File not found.” e nel log “Primary script unknown”: PHP-FPM non trova lo script. Controlla SCRIPT_FILENAME, root e percorsi nei container. https://daniele-michelin.com/it/errori/nginx-php-fpm-socket-13-permission-denied/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-fpm-socket-permission-denied.png nginx: socket PHP-FPM (13: Permission denied) · Daniele Michelin nginx dà 502 e registra connect() to unix:/run/php/...sock failed (13: Permission denied). L'utente nginx non può usare il socket PHP-FPM. Controlli e soluzione. https://daniele-michelin.com/it/errori/nginx-rewrite-or-internal-redirection-cycle/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-rewrite-redirection-cycle.png nginx: internal redirection cycle – soluzione · Daniele Michelin nginx registra rewrite or internal redirection cycle e risponde 500. try_files punta a un index.html mancante o il root è errato. Soluzione. https://daniele-michelin.com/it/errori/nginx-upstream-prematurely-closed-connection/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-upstream-prematurely-closed.png nginx: upstream prematurely closed connection – soluzione nginx risponde 502 e registra upstream prematurely closed connection while reading response header. Il backend è caduto, riavviato o parla un altro protocollo. https://daniele-michelin.com/it/errori/nginx-upstream-sent-too-big-header/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-too-big-header.png nginx: upstream sent too big header – soluzione · Daniele Michelin nginx scrive upstream sent too big header e risponde 502? Gli header del backend non entrano nel buffer. Come alzare i buffer fastcgi e proxy. https://daniele-michelin.com/it/errori/nginx-upstream-timed-out-110/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-upstream-timed-out.png nginx upstream timed out (110): cause e soluzione · Daniele Michelin nginx registra upstream timed out (110: Connection timed out) e gli utenti vedono 504. Come trovare il backend lento e alzare il timeout giusto. https://daniele-michelin.com/it/errori/nginx-worker-connections-are-not-enough/ https://daniele-michelin.com/assets/og/kb/it-e-nginx-worker-connections.png nginx: worker_connections are not enough – soluzione nginx registra worker_connections are not enough e le richieste falliscono o si bloccano. Limite di connessioni per worker raggiunto. Come verificare e alzarlo. https://daniele-michelin.com/it/errori/oidc-invalid-client-client-authentication-failed/ https://daniele-michelin.com/assets/og/kb/it-e-oidc-invalid-client.png OIDC: invalid_client all'endpoint dei token · Daniele Michelin Il login OIDC fallisce con invalid_client. Client secret errato o scaduto, metodo di autenticazione sbagliato o client ID inesistente. Controlli e soluzioni. https://daniele-michelin.com/it/errori/oidc-invalid-grant-token-endpoint/ https://daniele-michelin.com/assets/og/kb/it-e-oidc-invalid-grant.png OIDC invalid_grant: cause e soluzione · Daniele Michelin Errore OIDC “invalid_grant” sul token endpoint: codice scaduto o riusato, redirect_uri diversa, refresh token revocato o orologio sfasato. Come risolvere. https://daniele-michelin.com/it/errori/oidc-redirect-uri-mismatch-invalid-redirect-uri/ https://daniele-michelin.com/assets/og/kb/it-e-oidc-redirect-uri-mismatch.png OIDC redirect_uri_mismatch: cause e soluzione · Daniele Michelin Errore OIDC “redirect_uri_mismatch” o “Invalid parameter: redirect_uri”: l'URL di ritorno non coincide con quella registrata. Come trovare la differenza. https://daniele-michelin.com/it/errori/php-allowed-memory-size-exhausted/ https://daniele-michelin.com/assets/og/kb/it-e-php-memory-exhausted.png PHP: allowed memory size exhausted – soluzione · Daniele Michelin PHP Fatal error: Allowed memory size exhausted. Come alzare memory_limit nel php.ini giusto (FPM o CLI), trovare cosa consuma memoria ed evitare che si ripeta. https://daniele-michelin.com/it/errori/php-call-to-undefined-function-mysqli-connect/ https://daniele-michelin.com/assets/og/kb/it-e-php-mysqli-undefined-function.png PHP: Call to undefined function mysqli_connect() – soluzione PHP si ferma con Call to undefined function mysqli_connect() (o Class mysqli not found). L'estensione mysqli non è caricata nella versione PHP che serve il sito. https://daniele-michelin.com/it/errori/php-cannot-modify-header-information-headers-already-sent/ https://daniele-michelin.com/assets/og/kb/it-e-php-headers-already-sent.png PHP: Cannot modify header information – soluzione · Daniele Michelin PHP avvisa Cannot modify header information - headers already sent by (output started at file:riga). Output, BOM o spazi prima di header() o session_start(). https://daniele-michelin.com/it/errori/php-fpm-server-reached-pm-max-children/ https://daniele-michelin.com/assets/og/kb/it-e-php-fpm-max-children.png PHP-FPM: server reached pm.max_children – soluzione · Daniele Michelin PHP-FPM registra server reached pm.max_children e il sito rallenta o dà 502/504. Come dimensionare il pool dalla RAM e trovare le richieste lente. https://daniele-michelin.com/it/errori/php-maximum-execution-time-exceeded/ https://daniele-michelin.com/assets/og/kb/it-e-php-max-execution-time.png PHP: maximum execution time exceeded – soluzione · Daniele Michelin PHP Fatal error: Maximum execution time of 30 seconds exceeded. Come alzare max_execution_time, controllare il timeout di nginx e risolvere la parte lenta. https://daniele-michelin.com/it/errori/php-parse-error-unexpected-token/ https://daniele-michelin.com/assets/og/kb/it-e-php-parse-error-unexpected-token.png PHP: Parse error unexpected token · Daniele Michelin PHP Parse error: unexpected token significa che il file è sintatticamente rotto, spesso dopo un upgrade di PHP, un upload interrotto o un punto e virgola. https://daniele-michelin.com/it/errori/php-uploaded-file-exceeds-upload-max-filesize/ https://daniele-michelin.com/assets/og/kb/it-e-php-upload-max-filesize.png PHP: uploaded file exceeds upload_max_filesize – soluzione Gli upload falliscono con The uploaded file exceeds the upload_max_filesize directive in php.ini o POST Content-Length exceeds the limit. Quali limiti alzare e dove. https://daniele-michelin.com/it/errori/port-forwarding-non-funziona/ https://daniele-michelin.com/assets/og/kb/it-e-portfreigabe-geht-nicht.png Port forwarding non funziona: cause e controlli · Daniele Michelin Port forwarding nel router ma da fuori non si raggiunge nulla? Spesso c'entrano DS-Lite o CGNAT, altrimenti firewall o indirizzo sbagliato. Controlli passo passo. https://daniele-michelin.com/it/errori/postfix-deferred-connect-connection-timed-out/ https://daniele-michelin.com/assets/og/kb/it-e-postfix-connection-timed-out.png Postfix: connection timed out, mail in coda · Daniele Michelin Postfix status=deferred (connect to ...:25: Connection timed out). Porta 25 bloccata, firewall o problema IPv6. Controlli e soluzioni con relay sulla 587. https://daniele-michelin.com/it/errori/postfix-host-or-domain-name-not-found-name-service-error/ https://daniele-michelin.com/assets/og/kb/it-e-postfix-host-not-found.png Postfix: host or domain name not found – cause · Daniele Michelin Postfix status=deferred: Host or domain name not found, Name service error type=MX. Controlla resolver, chroot e dominio del destinatario. https://daniele-michelin.com/it/errori/postfix-hostname-does-not-resolve-to-address/ https://daniele-michelin.com/assets/og/kb/it-e-postfix-hostname-does-not-resolve.png Postfix: hostname does not resolve, soluzione · Daniele Michelin Avviso Postfix “hostname does not resolve to address”: DNS diretto e inverso del client non coincidono. Quando è innocuo e quando devi intervenire. https://daniele-michelin.com/it/errori/postfix-mail-for-domain-loops-back-to-myself/ https://daniele-michelin.com/assets/og/kb/it-e-postfix-mail-loops-back-to-myself.png Postfix: mail loops back to myself – soluzione · Daniele Michelin Postfix rimbalza con: mail for example.com loops back to myself. MX o relay puntano a questo server, ma il dominio qui non è configurato. Trova il ciclo e risolvi. https://daniele-michelin.com/it/errori/postfix-sasl-authentication-failed-no-mechanism-available/ https://daniele-michelin.com/assets/og/kb/it-e-postfix-sasl-authentication-failed.png Postfix: autenticazione SASL non riuscita · Daniele Michelin Postfix non accede al relay: SASL authentication failed, no mechanism available. Moduli libsasl2 mancanti, sasl_passwd o TLS. Soluzioni. https://daniele-michelin.com/it/errori/postgres-too-many-clients/ https://daniele-michelin.com/assets/og/kb/it-e-postgres-too-many-clients.png Postgres: FATAL too many clients already · Daniele Michelin “sorry, too many clients already” significa che max_connections è esaurito. Di solito sono pool aperti, un leak o transazioni idle: come misurarlo. https://daniele-michelin.com/it/errori/postgresql-fatal-no-pg-hba-conf-entry-for-host/ https://daniele-michelin.com/assets/og/kb/it-e-postgres-no-pg-hba-conf-entry.png PostgreSQL: no pg_hba.conf entry for host – soluzione PostgreSQL risponde FATAL: no pg_hba.conf entry for host. Nessuna regola consente indirizzo, utente, database o SSL. Controlla le regole e aggiungi una riga stretta. https://daniele-michelin.com/it/errori/postgresql-fatal-password-authentication-failed/ https://daniele-michelin.com/assets/og/kb/it-e-postgres-password-authentication-failed.png PostgreSQL: password authentication failed – soluzione PostgreSQL rifiuta l'accesso con FATAL: password authentication failed. Password errata, altra riga di pg_hba.conf o codifica dell'URL. Controlli e soluzioni. https://daniele-michelin.com/it/errori/raggiungere-nas-di-casa-da-fuori/ https://daniele-michelin.com/assets/og/kb/it-e-nas-von-unterwegs-erreichen.png Raggiungere il NAS di casa da fuori: VPN o porte · Daniele Michelin Come raggiungere NAS o PC di casa da fuori: VPN, port forwarding e DynDNS a confronto, con avvisi di sicurezza e comandi di verifica. https://daniele-michelin.com/it/errori/redis-oom-command-not-allowed/ https://daniele-michelin.com/assets/og/kb/it-e-redis-oom-command-not-allowed.png Redis: OOM command not allowed · Daniele Michelin Redis segnala “OOM command not allowed” quando la memoria supera maxmemory e non può eliminare chiavi. Ecco come tenere la cache scrivibile. https://daniele-michelin.com/it/errori/riavviare-router-correttamente/ https://daniele-michelin.com/assets/og/kb/it-e-router-neustart-richtig.png Riavviare il router nel modo giusto, e quando · Daniele Michelin Internet bloccato o Wi-Fi instabile? Riavvia il router nell'ordine corretto, verifica con ping che sia servito e scopri quando il riavvio non risolve nulla. https://daniele-michelin.com/it/errori/rsync-code-23-partial-transfer/ https://daniele-michelin.com/assets/og/kb/it-e-rsync-code-23-partial-transfer.png rsync: errore code 23 (file non trasferiti) · Daniele Michelin rsync esce con code 23 quando singoli file non sono stati trasferiti: permessi, file cambiati durante la copia o attributi. Il codice da solo dice poco. https://daniele-michelin.com/it/errori/saml-clock-skew-notbefore-timestamp-not-yet-valid/ https://daniele-michelin.com/assets/og/kb/it-e-saml-clock-skew.png SAML NotBefore / clock skew: errore di orario · Daniele Michelin Errore SAML “Could not validate timestamp: not yet valid” o NotBefore/NotOnOrAfter: gli orologi di IdP e SP non coincidono. Verifica e fix con NTP. https://daniele-michelin.com/it/errori/saml-invalid-audience-for-this-response/ https://daniele-michelin.com/assets/og/kb/it-e-saml-invalid-audience.png SAML: Invalid audience for this Response – soluzione Il login SAML fallisce con Invalid audience for this Response. L'Entity ID nell'IdP non coincide con quello del service provider. Confronta i due valori e correggi. https://daniele-michelin.com/it/errori/smart-tv-chromecast-non-si-collega/ https://daniele-michelin.com/assets/og/kb/it-e-smart-tv-chromecast-verbindet-nicht.png Smart TV o Chromecast non si collega: cause · Daniele Michelin Il casting non funziona e TV o Chromecast mancano nell'app? Controlla stessa rete, rete ospiti, 2,4 GHz e impostazioni del router passo passo. https://daniele-michelin.com/it/errori/smtp-421-4-7-0/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-421-470.png SMTP 421 4.7.0: rate limited – cause e soluzione · Daniele Michelin SMTP 421 4.7.0 significa che il destinatario sta limitando il tuo IP. Cause tipiche come PTR mancante o ondata di spam, diagnosi e soluzione. https://daniele-michelin.com/it/errori/smtp-450-4-1-8-sender-address-rejected-domain-not-found/ https://daniele-michelin.com/assets/og/kb/it-e-postfix-sender-domain-not-found.png SMTP: 450 4.1.8 Dominio mittente non trovato · Daniele Michelin Postfix rifiuta con 450 4.1.8 Sender address rejected: Domain not found. Il dominio del mittente non ha record A o MX. Controlla il DNS e correggi il mittente. https://daniele-michelin.com/it/errori/smtp-451-4-7-1-greylisting/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-451-471-greylisting.png SMTP 451 4.7.1 greylisting: cause e soluzione · Daniele Michelin SMTP 451 4.7.1 Greylisted è un ritardo voluto. Quando è normale, quando la posta resta bloccata e come regolare il greylisting di Postgrey o Rspamd. https://daniele-michelin.com/it/errori/smtp-530-5-7-0-must-issue-starttls/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-530-570-starttls.png SMTP 530 5.7.0: must issue STARTTLS, soluzione · Daniele Michelin SMTP 530 5.7.0 significa che il server vuole STARTTLS prima di accettare login o posta. Cause, verifica con openssl e impostazioni corrette del client. https://daniele-michelin.com/it/errori/smtp-535-5-7-8-authentication-failed/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-535-578.png SMTP 535 5.7.8: authentication failed, soluzione · Daniele Michelin SMTP 535 5.7.8 significa che il server ha rifiutato il login SMTP. Cause tipiche con Postfix/Dovecot, Gmail e Microsoft 365 e come verificarle. https://daniele-michelin.com/it/errori/smtp-550-5-1-1-user-unknown/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-550-511-user-unknown.png SMTP 550 5.1.1: user unknown, cause e soluzione · Daniele Michelin SMTP 550 5.1.1 significa che l'indirizzo del destinatario non esiste sul server. Controlla refusi, mappe delle caselle e classe di dominio in Postfix. https://daniele-michelin.com/it/errori/smtp-550-5-4-1-recipient-address-rejected-access-denied/ https://daniele-michelin.com/assets/og/kb/it-e-exchange-online-550-541-access-denied.png SMTP: 550 5.4.1 Recipient address rejected – soluzione Microsoft 365 rimbalza con 550 5.4.1 Recipient address rejected: Access denied. Destinatario assente nel tenant o tipo di dominio errato. Controlli e soluzioni. https://daniele-michelin.com/it/errori/smtp-550-5-7-1/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-550-571.png SMTP 550 5.7.1: Relay access denied – cause e soluzione SMTP 550 5.7.1 significa che il server rifiuta il relay o blocca per policy. Cause tipiche, verifica con postconf e soluzioni concrete. https://daniele-michelin.com/it/errori/smtp-550-5-7-26/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-550-5726.png SMTP 550 5.7.26 / 5.7.23: Gmail rifiuta per DMARC/SPF Gmail rifiuta con 550 5.7.26 o 5.7.23? SPF, DKIM o l'allineamento DMARC non tornano. Come controllare i record DNS e risolvere il bounce. https://daniele-michelin.com/it/errori/smtp-552-5-2-2-mailbox-full/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-552-522-mailbox-full.png SMTP 552 5.2.2: casella piena (quota), soluzione · Daniele Michelin SMTP 552 5.2.2 significa che la casella del destinatario ha raggiunto il limite di spazio. Come verificare la quota Dovecot e liberare spazio. https://daniele-michelin.com/it/errori/smtp-553-5-7-1-sender-address-rejected/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-553-571-sender-rejected.png SMTP 553 5.7.1: sender address rejected, soluzione · Daniele Michelin SMTP 553 5.7.1 significa che l'utente autenticato non può inviare con quel mittente. Come controllare smtpd_sender_login_maps e configurare il send-as. https://daniele-michelin.com/it/errori/smtp-554-5-7-1/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-554-571.png SMTP 554 5.7.1: rifiuto per blocklist, come risolvere SMTP 554 5.7.1 con blocked using: il tuo IP è in una blocklist come Spamhaus. Trova la causa, ferma lo spam e chiedi il delisting nel modo giusto. https://daniele-michelin.com/it/errori/smtp-554-5-7-1-relay-access-denied/ https://daniele-michelin.com/assets/og/kb/it-e-postfix-relay-access-denied.png SMTP: 554 5.7.1 Relay access denied – soluzione · Daniele Michelin Postfix risponde 554 5.7.1 Relay access denied: mittente senza login o dominio destinatario non gestito qui. Controlla le regole e risolvi senza open relay. https://daniele-michelin.com/it/errori/smtp-porta-25-bloccata/ https://daniele-michelin.com/assets/og/kb/it-e-smtp-port-25-gesperrt.png Porta 25 bloccata: invio mail impossibile · Daniele Michelin Molti provider e cloud bloccano la porta 25 in uscita. Le mail restano in coda e i timeout si accumulano. La soluzione è la submission con auth o un relay. https://daniele-michelin.com/it/errori/speed-test-troppo-lento/ https://daniele-michelin.com/assets/og/kb/it-e-speedtest-zu-langsam.png Speed test sotto il valore del contratto: cause · Daniele Michelin Lo speed test è sotto il valore del contratto? Contratto e realtà differiscono. Prova via cavo, controlla con ping e trova il collo di bottiglia nel Wi-Fi. https://daniele-michelin.com/it/errori/ssh-connect-to-host-port-22-connection-timed-out/ https://daniele-michelin.com/assets/og/kb/it-e-ssh-connection-timed-out.png SSH porta 22: connection timed out – cause · Daniele Michelin ssh: connect to host port 22: Connection timed out. Firewall, indirizzo errato, server spento o ban di fail2ban? Come capirlo e risolvere il problema. https://daniele-michelin.com/it/errori/ssh-connection-refused-port-22/ https://daniele-michelin.com/assets/og/kb/it-e-ssh-connection-refused.png SSH: connessione rifiutata sulla porta 22 · Daniele Michelin SSH Connection refused significa che sulla porta nessuno accetta connessioni. Di solito il servizio è fermo, ascolta altrove o il pacchetto viene rifiutato. https://daniele-michelin.com/it/errori/ssh-permission-denied-publickey/ https://daniele-michelin.com/assets/og/kb/it-e-ssh-permission-denied-publickey.png SSH: Permission denied (publickey), soluzione · Daniele Michelin SSH dice “Permission denied (publickey)”: utente sbagliato, chiave assente in authorized_keys, permessi errati o ssh-rsa disattivato. Verifica passo passo. https://daniele-michelin.com/it/errori/ssh-remote-host-identification-has-changed/ https://daniele-michelin.com/assets/og/kb/it-e-ssh-host-key-changed.png SSH: avviso host identification has changed · Daniele Michelin SSH avvisa REMOTE HOST IDENTIFICATION HAS CHANGED. Di solito una reinstallazione. Come verificare la chiave e correggere known_hosts in sicurezza. https://daniele-michelin.com/it/errori/ssh-too-many-authentication-failures/ https://daniele-michelin.com/assets/og/kb/it-e-ssh-too-many-authentication-failures.png SSH: too many authentication failures, cause · Daniele Michelin SSH si disconnette con Too many authentication failures prima della password. L'agent offre troppe chiavi. Usa IdentitiesOnly e MaxAuthTries. https://daniele-michelin.com/it/errori/ssl-certificate-has-expired/ https://daniele-michelin.com/assets/og/kb/it-e-tls-certificate-expired.png SSL: certificate has expired, soluzione · Daniele Michelin “certificate has expired” o NET::ERR_CERT_DATE_INVALID: rinnovo fallito, servizio non ricaricato oppure orologio sbagliato. Come verificare e risolvere. https://daniele-michelin.com/it/errori/ssl-error-rx-record-too-long/ https://daniele-michelin.com/assets/og/kb/it-e-tls-rx-record-too-long.png SSL_ERROR_RX_RECORD_TOO_LONG: cause e soluzione · Daniele Michelin Firefox mostra SSL_ERROR_RX_RECORD_TOO_LONG: sulla porta 443 il server risponde in HTTP in chiaro. Di solito manca “ssl” nella riga listen di nginx. https://daniele-michelin.com/it/errori/ssl-unable-to-get-local-issuer-certificate/ https://daniele-michelin.com/assets/og/kb/it-e-tls-unable-to-get-local-issuer.png unable to get local issuer certificate: soluzione · Daniele Michelin “SSL certificate problem: unable to get local issuer certificate” con curl, Python o Git: intermedi mancanti, bundle CA o TLS inspection. Soluzioni. https://daniele-michelin.com/it/errori/stampante-di-rete-non-trovata/ https://daniele-michelin.com/assets/og/kb/it-e-drucker-im-netzwerk-nicht-gefunden.png Stampante di rete non trovata: cause e soluzione · Daniele Michelin La stampante Wi-Fi non compare su PC o telefono? Cause tipiche come rete diversa o nuovo indirizzo IP e una verifica passo passo da fare in casa. https://daniele-michelin.com/it/errori/sudo-user-is-not-in-the-sudoers-file/ https://daniele-michelin.com/assets/og/kb/it-e-sudo-not-in-sudoers.png sudo: utente non presente nel file sudoers · Daniele Michelin sudo risponde “is not in the sudoers file. This incident will be reported.” Manca il gruppo sudo o una regola. Come controllare e aggiungerlo con usermod e visudo. https://daniele-michelin.com/it/errori/systemd-job-failed-control-process-exited-with-error-code/ https://daniele-michelin.com/assets/og/kb/it-e-systemd-job-failed-control-process.png systemd: job failed, control process: soluzione · Daniele Michelin “Job for X.service failed because the control process exited with error code”: come trovare il vero errore con systemctl status e journalctl, passo passo. https://daniele-michelin.com/it/errori/systemd-start-request-repeated-too-quickly/ https://daniele-michelin.com/assets/og/kb/it-e-systemd-start-limit-hit.png systemd: start-limit-hit, avvii troppo rapidi · Daniele Michelin systemd: Start request repeated too quickly, Failed with result start-limit-hit. Un ciclo di crash ha raggiunto il limite. Trova la causa e reimposta l'unità. https://daniele-michelin.com/it/errori/tar-unexpected-end-of-file/ https://daniele-michelin.com/assets/og/kb/it-e-tar-unexpected-end-of-file.png tar: unexpected end of file in estrazione · Daniele Michelin “unexpected end of file” significa che l'archivio è incompleto: download interrotto, disco pieno o processo fermato. Ecco come recuperare il resto. https://daniele-michelin.com/it/errori/temporary-failure-in-name-resolution/ https://daniele-michelin.com/assets/og/kb/it-e-linux-temporary-failure-name-resolution.png Temporary failure in name resolution – soluzione · Daniele Michelin ping, apt o curl segnalano Temporary failure in name resolution. Il server non raggiunge un resolver DNS: resolv.conf vuoto, resolved fermo o porta 53 bloccata. https://daniele-michelin.com/it/errori/tls-err-ssl-version-or-cipher-mismatch/ https://daniele-michelin.com/assets/og/kb/it-e-tls-version-cipher-mismatch.png ERR_SSL_VERSION_OR_CIPHER_MISMATCH: soluzione · Daniele Michelin ERR_SSL_VERSION_OR_CIPHER_MISMATCH: nessuna versione TLS o cipher in comune. Controlla ssl_protocols, ssl_ciphers e il certificato del virtual host. https://daniele-michelin.com/it/errori/trovare-indirizzo-ip-gateway/ https://daniele-michelin.com/assets/og/kb/it-e-ip-adresse-gateway-finden.png Trovare indirizzo IP e gateway (Win, Mac, Linux) · Daniele Michelin Non conosci l'indirizzo del router? Trova il tuo IP e il gateway predefinito con ipconfig, ip route o route e usali per aprire la pagina di gestione del router. https://daniele-michelin.com/it/errori/wifi-collegato-senza-internet/ https://daniele-michelin.com/assets/og/kb/it-e-wlan-verbunden-kein-internet.png Wi-Fi collegato ma senza internet: controlli · Daniele Michelin Il Wi-Fi c'è ma le pagine non si caricano? Controlla passo passo se la causa è router, linea internet o DNS, con comandi reali e soluzioni semplici. https://daniele-michelin.com/it/errori/wifi-continua-a-disconnettersi/ https://daniele-michelin.com/assets/og/kb/it-e-wlan-bricht-ab.png Wi-Fi si disconnette: cadute di connessione · Daniele Michelin Il Wi-Fi cade di continuo o si interrompe per un attimo? Cause semplici come interferenze, risparmio energetico e carico del router e controlli con comandi reali. https://daniele-michelin.com/it/errori/wifi-lento/ https://daniele-michelin.com/assets/og/kb/it-e-wlan-langsam.png Wi-Fi lento: cause e controlli a casa · Daniele Michelin Wi-Fi collegato ma lento? Controlli semplici su distanza, interferenze e router con comandi reali e soluzioni tipiche per la rete di casa, senza essere esperti. https://daniele-michelin.com/it/errori/wifi-ripetitore-o-mesh/ https://daniele-michelin.com/assets/og/kb/it-e-wlan-repeater-mesh.png Ripetitore Wi-Fi o mesh: cosa scegliere a casa · Daniele Michelin Zona morta in casa: ripetitore o mesh? Confronto generale, posizione giusta, controllo del segnale con comandi reali e quando un cavo è la soluzione migliore. https://daniele-michelin.com/it/glossario/acme/ https://daniele-michelin.com/assets/og/kb/it-g-acme.png Cos'è ACME? Certificati TLS automatici · Daniele Michelin ACME è il protocollo con cui Let's Encrypt e altre CA emettono certificati in automatico. HTTP-01, DNS-01, client come certbot e rinnovi falliti. https://daniele-michelin.com/it/glossario/autenticazione-a-piu-fattori/ https://daniele-michelin.com/assets/og/kb/it-g-mfa.png Cos'è l'MFA? Autenticazione a più fattori · Daniele Michelin L'MFA richiede al login, oltre alla password, un secondo fattore come codice da app, push o chiave di sicurezza. Metodi, punti deboli e supporto. https://daniele-michelin.com/it/glossario/bounce-ndr/ https://daniele-michelin.com/assets/og/kb/it-g-ndr.png Cos'è un bounce (NDR)? Leggere i messaggi d'errore · Daniele Michelin Un bounce o NDR segnala che una email non è stata consegnata. Come leggere il codice di stato, distinguere hard e soft bounce ed evitare il backscatter. https://daniele-michelin.com/it/glossario/caldav-carddav/ https://daniele-michelin.com/assets/og/kb/it-g-caldav-carddav.png Cosa sono CalDAV e CardDAV? La sync spiegata · Daniele Michelin CalDAV sincronizza i calendari e CardDAV i contatti, entrambi basati su WebDAV. Configurazione con Nextcloud, iOS, Android e Thunderbird e problemi tipici. https://daniele-michelin.com/it/glossario/catena-di-certificati/ https://daniele-michelin.com/assets/og/kb/it-g-cert-chain.png Cos'è una catena di certificati? Intermedi · Daniele Michelin La catena collega il certificato del server, tramite gli intermedi, a una root CA fidata. Perché serve la catena completa e come controllarla. https://daniele-michelin.com/it/glossario/codice-di-stato-http/ https://daniele-michelin.com/assets/og/kb/it-g-http-status.png Cos'è un codice di stato HTTP? Le classi · Daniele Michelin I codici di stato HTTP mostrano come il server ha risposto a una richiesta. Le cinque classi, codici chiave come 301, 403 e 502 e come leggerli nel debug. https://daniele-michelin.com/it/glossario/content-security-policy/ https://daniele-michelin.com/assets/og/kb/it-g-csp.png Cos'è una Content Security Policy (CSP)? · Daniele Michelin Una Content Security Policy stabilisce da quali sorgenti una pagina può caricare script, stili e frame. Direttive, modalità report-only e i guasti tipici. https://daniele-michelin.com/it/glossario/cron/ https://daniele-michelin.com/assets/og/kb/it-g-cron.png Cos'è un cron job? Cron su Linux spiegato · Daniele Michelin Cron esegue comandi a orari prestabiliti su Linux. Com'è fatta una riga di crontab, differenze con i timer systemd e fallimenti silenziosi. https://daniele-michelin.com/it/glossario/dkim/ https://daniele-michelin.com/assets/og/kb/it-g-dkim.png Cos'è DKIM? Le firme delle email spiegate · Daniele Michelin DKIM firma crittograficamente le email in uscita e pubblica la chiave pubblica nel DNS. Come funziona, cos'è il selector e perché compare dkim=fail. https://daniele-michelin.com/it/glossario/dmarc/ https://daniele-michelin.com/assets/og/kb/it-g-dmarc.png Cos'è DMARC? Policy e report spiegati · Daniele Michelin DMARC collega SPF e DKIM all'indirizzo From visibile e dice ai destinatari cosa fare con la posta falsificata. Allineamento, policy e report aggregati. https://daniele-michelin.com/it/glossario/dnssec/ https://daniele-michelin.com/assets/og/kb/it-g-dnssec.png Cos'è DNSSEC? Risposte DNS firmate · Daniele Michelin DNSSEC firma i record DNS così i resolver riconoscono risposte falsificate. Come funziona, a cosa serve il record DS e perché un errore spegne il dominio. https://daniele-michelin.com/it/glossario/escalation/ https://daniele-michelin.com/assets/og/kb/it-g-escalation.png Cos'è un'escalation nel supporto IT? · Daniele Michelin Un'escalation passa un ticket a un livello di supporto superiore o avvisa il management. Escalation funzionale e gerarchica, buoni passaggi. https://daniele-michelin.com/it/glossario/file-descriptor/ https://daniele-michelin.com/assets/og/kb/it-g-file-descriptor.png Cos'è un file descriptor? I limiti spiegati · Daniele Michelin Un file descriptor è il numero con cui un processo usa file e socket aperti. Da dove nasce Too many open files e come alzare il limite in modo corretto. https://daniele-michelin.com/it/glossario/glue-record/ https://daniele-michelin.com/assets/og/kb/it-g-glue.png Cos'è un glue record? La delega DNS spiegata · Daniele Michelin I glue record sono gli IP dei name server pubblicati nella zona padre. Quando servono, come impostarli e cosa si rompe quando sono sbagliati. https://daniele-michelin.com/it/glossario/greylisting/ https://daniele-michelin.com/assets/og/kb/it-g-greylisting.png Cos'è il greylisting? Antispam con ritardo · Daniele Michelin Il greylisting rifiuta in modo temporaneo la posta da mittenti sconosciuti e la accetta al nuovo tentativo. Come funziona, svantaggi e come riconoscerlo. https://daniele-michelin.com/it/glossario/hsts/ https://daniele-michelin.com/assets/og/kb/it-g-hsts.png Cos'è HSTS? HTTP Strict Transport Security · Daniele Michelin HSTS dice ai browser di aprire un dominio solo via HTTPS. Sintassi dell'header, max-age, includeSubDomains, preload e perché tornare indietro è difficile. https://daniele-michelin.com/it/glossario/identity-provider/ https://daniele-michelin.com/assets/og/kb/it-g-idp.png Cos'è un identity provider (IdP)? · Daniele Michelin Un identity provider gestisce gli account utente e conferma alle applicazioni, via SAML o OIDC, chi ha fatto login. Esempi, ruolo e rischi se si ferma. https://daniele-michelin.com/it/glossario/imap/ https://daniele-michelin.com/assets/og/kb/it-g-imap.png Cos'è IMAP? L'accesso alla casella spiegato · Daniele Michelin IMAP è il protocollo con cui i client di posta accedono a una casella sul server. Differenza con POP3, porte 143 e 993 e problemi più frequenti. https://daniele-michelin.com/it/glossario/ https://daniele-michelin.com/assets/og/kb/it-hub-glossary.png Glossario IT per admin: DNS, mail, TLS, SSO · Daniele Michelin Termini di DNS, e-mail, TLS, single sign-on e gestione Linux spiegati in breve e in modo pratico — con esempi e comandi. https://daniele-michelin.com/it/glossario/inode/ https://daniele-michelin.com/assets/og/kb/it-g-inode.png Cos'è un inode? Il file system Linux spiegato · Daniele Michelin Un inode contiene i metadati di un file nel file system Linux. Perché un disco può risultare pieno con spazio libero e come trovare la causa. https://daniele-michelin.com/it/glossario/journald/ https://daniele-michelin.com/assets/og/kb/it-g-journald.png Cos'è journald? Leggere i log con systemd · Daniele Michelin journald raccoglie i log di tutti i servizi sotto systemd in un journal binario. I comandi journalctl principali, limiti di spazio e log persistenti. https://daniele-michelin.com/it/glossario/json-web-token/ https://daniele-michelin.com/assets/og/kb/it-g-jwt.png Cos'è un JWT? Il JSON Web Token spiegato · Daniele Michelin Un JWT è un token firmato composto da header, payload e firma, usato in OIDC e nelle API. Struttura, validazione, scadenza ed errori di sicurezza comuni. https://daniele-michelin.com/it/glossario/livelli-di-supporto/ https://daniele-michelin.com/assets/og/kb/it-g-support-levels.png Supporto di 1°, 2° e 3° livello: differenze · Daniele Michelin I livelli di supporto dividono le richieste per complessità: ricezione e casi standard, analisi tecnica, sviluppo e produttore. Compiti e passaggi. https://daniele-michelin.com/it/glossario/logrotate/ https://daniele-michelin.com/assets/og/kb/it-g-logrotate.png Cos'è logrotate? Ruotare i file di log · Daniele Michelin logrotate ruota, comprime e cancella in automatico i vecchi file di log. Com'è fatta una configurazione, copytruncate contro postrotate ed errori tipici. https://daniele-michelin.com/it/glossario/mta-mail-transfer-agent/ https://daniele-michelin.com/assets/og/kb/it-g-mta.png Cos'è un MTA? Il mail transfer agent spiegato · Daniele Michelin Un MTA riceve le email via SMTP e le passa al server successivo, per esempio Postfix o Exim. Differenza con MUA e MDA e a cosa serve la coda. https://daniele-michelin.com/it/glossario/mta-sts/ https://daniele-michelin.com/assets/og/kb/it-g-mta-sts.png Cos'è MTA-STS? TLS obbligatorio per la posta · Daniele Michelin MTA-STS obbliga i mail server mittenti a consegnare via TLS con certificato valido. Record TXT, file di policy, modalità testing ed enforce, errori tipici. https://daniele-michelin.com/it/glossario/name-server-autoritativo/ https://daniele-michelin.com/assets/og/kb/it-g-authoritative.png Cos'è un name server autoritativo? · Daniele Michelin Un name server autoritativo contiene i dati originali di una zona DNS e dà risposte definitive. Differenza con il resolver e come interrogarlo. https://daniele-michelin.com/it/glossario/nextcloud/ https://daniele-michelin.com/assets/og/kb/it-g-nextcloud.png Cos'è Nextcloud? L'architettura per admin · Daniele Michelin Nextcloud è una piattaforma self-hosted per file, calendari, contatti e collaborazione. I componenti: PHP, database, cache e storage, e come gestirla. https://daniele-michelin.com/it/glossario/nxdomain/ https://daniele-michelin.com/assets/og/kb/it-g-nxdomain.png Cosa significa NXDOMAIN? L'errore DNS spiegato · Daniele Michelin NXDOMAIN significa che il nome richiesto non esiste nel DNS. Differenza con NODATA e SERVFAIL, cause tipiche e diagnosi rapida con il comando dig. https://daniele-michelin.com/it/glossario/oauth-2-0/ https://daniele-michelin.com/assets/og/kb/it-g-oauth2.png Cos'è OAuth 2.0? L'autorizzazione spiegata · Daniele Michelin OAuth 2.0 permette alle applicazioni di accedere a risorse senza conoscere la password dell'utente. Ruoli, access e refresh token e flussi attuali. https://daniele-michelin.com/it/glossario/object-storage-s3/ https://daniele-michelin.com/assets/og/kb/it-g-s3.png Cos'è l'object storage S3? Il bucket spiegato · Daniele Michelin L'object storage S3 conserva i dati come oggetti in bucket, accessibili via API HTTP. Differenze con un file system, uso con Nextcloud ed errori tipici. https://daniele-michelin.com/it/glossario/oom-killer/ https://daniele-michelin.com/assets/og/kb/it-g-oom-killer.png Cos'è l'OOM killer? La memoria su Linux · Daniele Michelin L'OOM killer termina i processi su Linux quando la memoria finisce. Come sceglie la vittima, come trovarlo nei log e cosa risolve davvero il problema. https://daniele-michelin.com/it/glossario/openid-connect/ https://daniele-michelin.com/assets/og/kb/it-g-oidc.png Cos'è OpenID Connect (OIDC)? Spiegazione · Daniele Michelin OpenID Connect aggiunge login e identità a OAuth 2.0. ID token, documento di discovery, client ID e redirect URI e gli errori tipici della configurazione. https://daniele-michelin.com/it/glossario/php-fpm/ https://daniele-michelin.com/assets/og/kb/it-g-php-fpm.png Cos'è PHP-FPM e come impostare pm.max_children · Daniele Michelin PHP-FPM esegue PHP in un pool di processi via FastCGI. Come calcolare pm.max_children dalla RAM, un esempio di configurazione e le cause di 502/504. https://daniele-michelin.com/it/glossario/propagazione-dns/ https://daniele-michelin.com/assets/og/kb/it-g-propagation.png Cos'è la propagazione DNS? Quanto dura? · Daniele Michelin La propagazione DNS è il tempo che serve perché tutti i resolver vedano una risposta DNS modificata. Perché dipende dal TTL e come verificarla. https://daniele-michelin.com/it/glossario/record-a-aaaa/ https://daniele-michelin.com/assets/og/kb/it-g-a-aaaa.png Cos'è un record A? Record AAAA e IPv6 · Daniele Michelin Un record A associa un hostname a un indirizzo IPv4, il record AAAA a un IPv6. Come funzionano, come verificarli con dig e gli errori dual-stack. https://daniele-michelin.com/it/glossario/record-caa/ https://daniele-michelin.com/assets/og/kb/it-g-caa.png Cos'è un record CAA? Chi può emettere certificati · Daniele Michelin Un record CAA stabilisce quali autorità di certificazione possono emettere certificati per il tuo dominio. Sintassi, esempio e errori con ACME. https://daniele-michelin.com/it/glossario/record-cname/ https://daniele-michelin.com/assets/og/kb/it-g-cname.png Cos'è un record CNAME? Alias nel DNS · Daniele Michelin Un record CNAME rende un nome DNS alias di un altro. Quando usarlo, perché non è ammesso all'apex della zona e gli errori che lo rendono inutile. https://daniele-michelin.com/it/glossario/record-mx/ https://daniele-michelin.com/assets/og/kb/it-g-mx.png Cos'è un record MX? Instradamento mail nel DNS · Daniele Michelin Il record MX indica quale server riceve le email di un dominio. Priorità, verifica con dig e gli errori più comuni quando cambi provider di posta. https://daniele-michelin.com/it/glossario/record-ns/ https://daniele-michelin.com/assets/og/kb/it-g-ns.png Cos'è un record NS? La delega nel DNS · Daniele Michelin I record NS indicano quali name server sono responsabili di una zona. Delega presso il registro, verifica con dig e trappole quando cambi provider DNS. https://daniele-michelin.com/it/glossario/record-ptr/ https://daniele-michelin.com/assets/og/kb/it-g-ptr.png Cos'è un record PTR? Il reverse DNS spiegato · Daniele Michelin Un record PTR risolve un indirizzo IP in un hostname. Perché serve ai mail server, chi lo gestisce e come verificare il reverse DNS con dig. https://daniele-michelin.com/it/glossario/record-soa/ https://daniele-michelin.com/assets/og/kb/it-g-soa.png Cos'è un record SOA? I campi spiegati · Daniele Michelin Il record SOA apre ogni zona DNS. Cosa significano serial, refresh, retry, expire e minimum, e perché il numero di serie è così importante. https://daniele-michelin.com/it/glossario/record-srv/ https://daniele-michelin.com/assets/og/kb/it-g-srv.png Cos'è un record SRV? Trovare servizi nel DNS · Daniele Michelin Un record SRV pubblica host e porta di un servizio come Autodiscover, CalDAV, SIP o XMPP. Struttura dei campi, esempio e verifica con il comando dig. https://daniele-michelin.com/it/glossario/record-txt/ https://daniele-michelin.com/assets/og/kb/it-g-txt.png Cos'è un record TXT? Usi e limiti · Daniele Michelin I record TXT contengono testo libero nel DNS e ospitano SPF, DKIM, DMARC e codici di verifica. Formato, limite dei 255 caratteri ed errori comuni. https://daniele-michelin.com/it/glossario/relay-open-relay/ https://daniele-michelin.com/assets/og/kb/it-g-open-relay.png Cos'è un relay di posta? L'open relay spiegato · Daniele Michelin Un relay inoltra email verso domini di cui non è responsabile. Quando è voluto, perché un open relay è pericoloso e da dove nasce Relay access denied. https://daniele-michelin.com/it/glossario/resolver-dns/ https://daniele-michelin.com/assets/og/kb/it-g-resolver.png Cos'è un resolver DNS? La ricorsione spiegata · Daniele Michelin Un resolver DNS risponde alle query dei client percorrendo la catena dalla root alla zona giusta e mettendo in cache il risultato. Funzionamento e debug. https://daniele-michelin.com/it/glossario/reverse-proxy/ https://daniele-michelin.com/assets/og/kb/it-g-reverse-proxy.png Cos'è un reverse proxy? A cosa serve · Daniele Michelin Un reverse proxy riceve le richieste e le inoltra ai server di backend, per esempio nginx davanti a Nextcloud. Compiti, header ed errori tipici. https://daniele-michelin.com/it/glossario/root-cause-analysis/ https://daniele-michelin.com/assets/og/kb/it-g-rca.png Cos'è una root cause analysis (RCA)? · Daniele Michelin Una root cause analysis cerca la causa reale di un incidente, non solo il sintomo. Il processo, i 5 perché e un buon report. https://daniele-michelin.com/it/glossario/rpo-rto/ https://daniele-michelin.com/assets/og/kb/it-g-rpo-rto.png Cosa sono RPO e RTO? Obiettivi di ripristino · Daniele Michelin L'RPO indica quanta perdita di dati è accettabile, l'RTO in quanto tempo un sistema deve ripartire. Esempi, impatto sui backup e perché testare il restore. https://daniele-michelin.com/it/glossario/saml/ https://daniele-michelin.com/assets/og/kb/it-g-saml.png Cos'è SAML? Il protocollo SSO spiegato · Daniele Michelin SAML 2.0 è un protocollo basato su XML per il single sign-on tra identity provider e applicazione. Flusso, metadati, certificati ed errori tipici. https://daniele-michelin.com/it/glossario/scim/ https://daniele-michelin.com/assets/og/kb/it-g-scim.png Cos'è SCIM? Il provisioning utenti spiegato · Daniele Michelin SCIM sincronizza in automatico utenti e gruppi dall'identity provider alle applicazioni. Differenza con l'SSO, funzionamento e trappole più comuni. https://daniele-michelin.com/it/glossario/server-name-indication/ https://daniele-michelin.com/assets/og/kb/it-g-sni.png Cos'è SNI? Server Name Indication spiegato · Daniele Michelin SNI comunica al server, durante l'handshake TLS, quale hostname vuole il client, così più siti HTTPS condividono un IP. Funzionamento e problemi tipici. https://daniele-michelin.com/it/glossario/service-level-agreement/ https://daniele-michelin.com/assets/og/kb/it-g-sla.png Cos'è uno SLA? Service level agreement · Daniele Michelin Uno SLA definisce obiettivi misurabili come tempo di risposta, tempo di risoluzione e disponibilità. Termini chiave, cosa vuol dire 99,9% e trappole. https://daniele-michelin.com/it/glossario/service-provider/ https://daniele-michelin.com/assets/og/kb/it-g-sp.png Cos'è un service provider (SP) nell'SSO? · Daniele Michelin Nell'SSO il service provider è l'applicazione che si fida dell'identity provider, per esempio Nextcloud con SAML. Entity ID, URL ACS ed errori comuni. https://daniele-michelin.com/it/glossario/single-sign-on/ https://daniele-michelin.com/assets/og/kb/it-g-sso.png Cos'è il single sign-on (SSO)? Spiegazione · Daniele Michelin Con l'SSO gli utenti accedono una volta all'identity provider e raggiungono più applicazioni. Protocolli coinvolti, vantaggi operativi e trappole comuni. https://daniele-michelin.com/it/glossario/smtp/ https://daniele-michelin.com/assets/og/kb/it-g-smtp.png Cos'è SMTP? L'invio delle email spiegato · Daniele Michelin SMTP è il protocollo con cui i mail server si consegnano le email. Come funziona una sessione, le porte 25, 587 e 465 e come leggere i codici di risposta. https://daniele-michelin.com/it/glossario/snapshot-vs-backup/ https://daniele-michelin.com/assets/og/kb/it-g-snapshot-backup.png Snapshot o backup? La differenza spiegata · Daniele Michelin Uno snapshot congela lo stato di un volume, un backup è una copia indipendente conservata altrove. Perché gli snapshot da soli non sono un backup. https://daniele-michelin.com/it/glossario/spf/ https://daniele-michelin.com/assets/og/kb/it-g-spf.png Cos'è SPF? Sender Policy Framework spiegato · Daniele Michelin SPF usa un record TXT per indicare quali server possono inviare posta per un dominio. Sintassi, il limite di 10 lookup DNS e gli errori più comuni. https://daniele-michelin.com/it/glossario/starttls/ https://daniele-michelin.com/assets/og/kb/it-g-starttls.png Cos'è STARTTLS? Passare a una connessione cifrata · Daniele Michelin STARTTLS porta una connessione SMTP, IMAP o POP3 in chiaro su TLS. Come funziona, differenza con il TLS implicito e i suoi punti deboli noti. https://daniele-michelin.com/it/glossario/subject-alternative-name/ https://daniele-michelin.com/assets/og/kb/it-g-san.png Cos'è un SAN? Subject Alternative Name · Daniele Michelin Il Subject Alternative Name elenca tutti gli hostname per cui vale un certificato TLS. Perché il Common Name non conta più e come controllare i SAN. https://daniele-michelin.com/it/glossario/submission-porta-587/ https://daniele-michelin.com/assets/og/kb/it-g-submission.png Cos'è la submission? Porta 587, 25 e 465 · Daniele Michelin La submission è il servizio SMTP usato da client e applicazioni per inviare posta. Differenze tra porta 587, 25 e 465 e perché serve l'autenticazione. https://daniele-michelin.com/it/glossario/tls/ https://daniele-michelin.com/assets/og/kb/it-g-tls.png Cos'è TLS? Transport Layer Security spiegato · Daniele Michelin TLS cifra connessioni come HTTPS, IMAPS e SMTP e dimostra l'identità del server con un certificato. L'handshake, le versioni e gli errori più comuni. https://daniele-michelin.com/it/glossario/ttl/ https://daniele-michelin.com/assets/og/kb/it-g-ttl.png Cos'è il TTL nel DNS? Time to live spiegato · Daniele Michelin Il TTL stabilisce per quanto i resolver tengono in cache un record DNS. Valori sensati, come abbassarlo prima di una migrazione ed equivoci comuni. https://daniele-michelin.com/it/glossario/unit-systemd/ https://daniele-michelin.com/assets/og/kb/it-g-systemd-unit.png Cos'è una unit systemd? I file unit spiegati · Daniele Michelin Una unit systemd descrive un servizio, timer o mount gestito da systemd. Struttura del file unit, override e come trovare gli errori di avvio. https://daniele-michelin.com/it/glossario/webdav/ https://daniele-michelin.com/assets/og/kb/it-g-webdav.png Cos'è WebDAV? Accesso ai file via HTTP · Daniele Michelin WebDAV estende HTTP con metodi per leggere, scrivere e gestire file su un server. Come lo usa Nextcloud, quali client lo supportano ed errori frequenti. https://daniele-michelin.com/it/porte/110/ https://daniele-michelin.com/assets/og/kb/it-p-110.png Porta 110: POP3 con STARTTLS · Daniele Michelin Porta 110 per POP3: scaricare la posta con STARTTLS, perché è meglio la porta 995 con TLS implicito e quando puoi chiudere del tutto la 110. https://daniele-michelin.com/it/porte/11211/ https://daniele-michelin.com/assets/og/kb/it-p-11211.png Porta 11211: Memcached solo in locale · Daniele Michelin Porta 11211 per Memcached: la cache dietro molte app PHP. Perché UDP 11211 è stata sfruttata per DDoS record e come mettere in sicurezza Memcached. https://daniele-michelin.com/it/porte/1194/ https://daniele-michelin.com/assets/og/kb/it-p-1194.png Porta 1194: OpenVPN su UDP · Daniele Michelin Porta 1194 per OpenVPN: di default UDP, con TCP o porta 443 come ripiego. Regole firewall, problemi di MTU e il confronto con WireGuard. https://daniele-michelin.com/it/porte/123/ https://daniele-michelin.com/assets/og/kb/it-p-123.png Porta 123: sincronizzazione NTP · Daniele Michelin Porta 123/UDP per NTP: perché l'ora esatta conta per TLS, Kerberos e 2FA, se la porta va aperta e come verificare la sincronizzazione su Linux. https://daniele-michelin.com/it/porte/143/ https://daniele-michelin.com/assets/og/kb/it-p-143.png Porta 143: IMAP con STARTTLS · Daniele Michelin Porta 143 per IMAP: accesso alla casella con STARTTLS, differenza con la porta 993 e perché devi bloccare i login in chiaro sulla porta 143. https://daniele-michelin.com/it/porte/20-21/ https://daniele-michelin.com/assets/og/kb/it-p-20-21.png Porta 20/21: FTP e i problemi col firewall · Daniele Michelin La porta 21 è il canale di controllo FTP, la 20 il canale dati in active mode. Perché FTP richiede porte passive e quando conviene passare a SFTP. https://daniele-michelin.com/it/porte/2049/ https://daniele-michelin.com/assets/og/kb/it-p-2049.png Porta 2049: condivisioni NFS in LAN · Daniele Michelin Porta 2049 per NFS: NFSv4 usa solo questa porta, NFSv3 richiede anche rpcbind e mountd. Regole firewall, problemi di permessi e sicurezza. https://daniele-michelin.com/it/porte/22/ https://daniele-michelin.com/assets/og/kb/it-p-22.png Porta 22: SSH e SFTP in sicurezza · Daniele Michelin Porta 22 per SSH e SFTP: cosa gira, come proteggere l'accesso con chiavi, Fail2ban e filtro IP, e come risolvere i classici errori di login. https://daniele-michelin.com/it/porte/25/ https://daniele-michelin.com/assets/og/kb/it-p-25.png Porta 25: SMTP tra server di posta · Daniele Michelin La porta 25 serve al trasporto della posta tra server (MX), non ai client. Perché i provider bloccano la 25 in uscita e come testare STARTTLS. https://daniele-michelin.com/it/porte/3306/ https://daniele-michelin.com/assets/og/kb/it-p-3306.png Porta 3306: MySQL e MariaDB · Daniele Michelin Porta 3306 per MySQL e MariaDB: perché il database non deve essere pubblico, bind-address, tunnel SSH e gli errori di connessione più comuni. https://daniele-michelin.com/it/porte/3389/ https://daniele-michelin.com/assets/og/kb/it-p-3389.png Porta 3389: RDP in sicurezza · Daniele Michelin Porta 3389 per Desktop remoto (RDP): perché non va mai esposta direttamente su Internet, NLA, VPN o RD Gateway e gli errori di connessione tipici. https://daniele-michelin.com/it/porte/3478/ https://daniele-michelin.com/assets/og/kb/it-p-3478.png Porta 3478: STUN/TURN per Nextcloud Talk · Daniele Michelin Porta 3478 per STUN/TURN con coturn: come funzionano le chiamate di Nextcloud Talk dietro NAT. Firewall, porte relay, external-ip ed errori. https://daniele-michelin.com/it/porte/389/ https://daniele-michelin.com/assets/og/kb/it-p-389.png Porta 389: LDAP e StartTLS · Daniele Michelin Porta 389 per LDAP e Active Directory: accesso alla directory con StartTLS, perché non va mai esposta su Internet ed errori di bind tipici. https://daniele-michelin.com/it/porte/4190/ https://daniele-michelin.com/assets/og/kb/it-p-4190.png Porta 4190: ManageSieve per i filtri mail · Daniele Michelin Porta 4190 per ManageSieve: gestisci filtri lato server e risposte automatiche con Sieve da Roundcube, Thunderbird e Nextcloud Mail. https://daniele-michelin.com/it/porte/443/ https://daniele-michelin.com/assets/og/kb/it-p-443.png Porta 443: HTTPS, TLS e HTTP/3 · Daniele Michelin Porta 443 per HTTPS: TCP per TLS, UDP per HTTP/3 (QUIC). Come verificare catena dei certificati e SNI e risolvere i classici errori TLS. https://daniele-michelin.com/it/porte/465/ https://daniele-michelin.com/assets/og/kb/it-p-465.png Porta 465: SMTPS con TLS implicito · Daniele Michelin Porta 465 per l'invio di posta con TLS implicito, di nuovo raccomandata dalla RFC 8314. Differenze con la porta 587 ed errori tipici dei client. https://daniele-michelin.com/it/porte/51820/ https://daniele-michelin.com/assets/og/kb/it-p-51820.png Porta 51820: VPN WireGuard · Daniele Michelin Porta 51820/UDP per WireGuard: il ListenPort abituale, perché le scansioni non la vedono e come risolvere problemi di handshake, NAT e MTU. https://daniele-michelin.com/it/porte/53/ https://daniele-michelin.com/assets/og/kb/it-p-53.png Porta 53: DNS su UDP e TCP · Daniele Michelin Porta 53 per il DNS: perché oltre a UDP serve anche TCP, quando può essere pubblica e come i resolver aperti vengono sfruttati per attacchi DDoS. https://daniele-michelin.com/it/porte/5432/ https://daniele-michelin.com/assets/og/kb/it-p-5432.png Porta 5432: PostgreSQL in sicurezza · Daniele Michelin Porta 5432 per PostgreSQL: listen_addresses, pg_hba.conf e perché il database non deve essere pubblico. Come risolvere gli errori di connessione. https://daniele-michelin.com/it/porte/587/ https://daniele-michelin.com/assets/og/kb/it-p-587.png Porta 587: SMTP submission con STARTTLS · Daniele Michelin Porta 587 per l'invio di posta dai client: submission con STARTTLS e login obbligatorio. Porta 587 o 465? Differenze ed errori più comuni. https://daniele-michelin.com/it/porte/636/ https://daniele-michelin.com/assets/og/kb/it-p-636.png Porta 636: LDAPS con TLS implicito · Daniele Michelin Porta 636 per LDAPS: LDAP su TLS implicito per Nextcloud, posta e Active Directory. Come risolvere i problemi di certificato e limitare l'accesso. https://daniele-michelin.com/it/porte/6379/ https://daniele-michelin.com/assets/og/kb/it-p-6379.png Porta 6379: Redis mai pubblico · Daniele Michelin Porta 6379 per Redis: perché le istanze Redis aperte vengono compromesse, protected-mode, password, socket Unix e Redis come cache di Nextcloud. https://daniele-michelin.com/it/porte/80/ https://daniele-michelin.com/assets/og/kb/it-p-80.png Porta 80: HTTP, redirect e ACME · Daniele Michelin Porta 80 per HTTP: perché tenerla aperta anche con HTTPS, come la usa la challenge HTTP-01 di Let's Encrypt e quali errori di redirect evitare. https://daniele-michelin.com/it/porte/8080/ https://daniele-michelin.com/assets/og/kb/it-p-8080.png Porta 8080: porta HTTP alternativa · Daniele Michelin Porta 8080 come porta HTTP alternativa per proxy, Tomcat, container Docker e backend. Perché non deve essere pubblica e la trappola di Docker. https://daniele-michelin.com/it/porte/8443/ https://daniele-michelin.com/assets/og/kb/it-p-8443.png Porta 8443: HTTPS alternativo e Plesk · Daniele Michelin Porta 8443 come porta HTTPS alternativa: pannello Plesk, Tomcat, UniFi e interfacce admin. Come limitare l'accesso e risolvere errori TLS. https://daniele-michelin.com/it/porte/853/ https://daniele-michelin.com/assets/og/kb/it-p-853.png Porta 853: DNS over TLS (DoT) · Daniele Michelin Porta 853 per DNS over TLS e DNS over QUIC: query DNS cifrate, DNS privato su Android, regole firewall e differenze rispetto a DNS over HTTPS. https://daniele-michelin.com/it/porte/9000/ https://daniele-michelin.com/assets/og/kb/it-p-9000.png Porta 9000: PHP-FPM e FastCGI · Daniele Michelin Porta 9000 per PHP-FPM: FastCGI tra nginx e PHP, perché una porta 9000 esposta permette l'esecuzione di codice e come risolvere gli errori 502. https://daniele-michelin.com/it/porte/9090/ https://daniele-michelin.com/assets/og/kb/it-p-9090.png Porta 9090: server Prometheus e Cockpit · Daniele Michelin Porta 9090 per il server Prometheus: interfaccia web e API senza login integrato. Anche Cockpit usa la 9090. Protezione e diagnosi dei target. https://daniele-michelin.com/it/porte/9100/ https://daniele-michelin.com/assets/og/kb/it-p-9100.png Porta 9100: Prometheus node_exporter · Daniele Michelin Porta 9100 per il node_exporter di Prometheus: metriche di sistema per il monitoraggio. Perché la porta va aperta solo al server Prometheus. https://daniele-michelin.com/it/porte/993/ https://daniele-michelin.com/assets/og/kb/it-p-993.png Porta 993: IMAPS con TLS implicito · Daniele Michelin Porta 993 per IMAPS: accesso alla casella con TLS implicito, l'impostazione raccomandata per i client di posta. Problemi di certificato e login. https://daniele-michelin.com/it/porte/995/ https://daniele-michelin.com/assets/og/kb/it-p-995.png Porta 995: POP3S con TLS implicito · Daniele Michelin Porta 995 per POP3S: scaricare la posta con TLS implicito. Quando POP3 ha ancora senso, come proteggere la porta e perché spariscono le mail. https://daniele-michelin.com/it/porte/ https://daniele-michelin.com/assets/og/kb/it-hub-ports.png Porte di rete per admin: elenco con spiegazioni · Daniele Michelin Le porte TCP/UDP principali per mail, web, DNS, database e VPN: cosa ci gira, se deve essere aperta e come verificarla. https://daniele-michelin.com/it/progetti/acestudio-mac/ https://daniele-michelin.com/assets/og/projects/acestudio-mac-it.png ACE Studio – App macOS per musica AI locale · Daniele Michelin ACE Studio è un'interfaccia SwiftUI per un'installazione locale di ACE-Step 1.5: si descrive una canzone, l'app scrive testo e stile, pilota il motore e… https://daniele-michelin.com/it/progetti/ai-receptionist/ https://daniele-michelin.com/assets/og/projects/ai-receptionist-it.png Local AI Receptionist – Receptionist AI telefonico, tutto in locale Un receptionist AI che risponde al telefono (numero Twilio) o dal browser, prende appuntamenti e parla italiano (con accento milanese) e tedesco. https://daniele-michelin.com/it/progetti/famiglia-os/ https://daniele-michelin.com/assets/og/projects/famiglia-os-it.png FamigliaOS – La casa digitale, self-hosted · Daniele Michelin FamigliaOS vuole riunire in un unico posto calendario, compiti, pianificazione dei pasti e altro per tutta la famiglia – come app self-hosted in un solo… https://daniele-michelin.com/it/progetti/jarvis/ https://daniele-michelin.com/assets/og/projects/jarvis-it.png J.A.R.V.I.S. – Assistente AI per macOS, 120+ strumenti J.A.R.V.I.S. è un assistente AI dall'aspetto cyberpunk per macOS: backend Python/FastAPI, frontend Vite/TypeScript, input di testo, voce e immagini. Tutti i… https://daniele-michelin.com/it/progetti/job-hunter/ https://daniele-michelin.com/assets/og/projects/job-hunter-it.png job-hunter – Assistente self-hosted per cercare lavoro job-hunter trova ogni mattina nuovi annunci, li valuta rispetto al proprio profilo e scrive con l'AI una breve lettera di presentazione in tedesco. https://daniele-michelin.com/it/progetti/llm-wiki/ https://daniele-michelin.com/assets/og/projects/llm-wiki-it.png LLM-Wiki – RAG sui propri documenti · Daniele Michelin LLM-Wiki è un sistema RAG per i propri documenti: si fanno domande a testo o a voce e si ottengono risposte supportate dalle fonti da cui provengono. https://daniele-michelin.com/it/progetti/zimage-turbo-pipeline/ https://daniele-michelin.com/assets/og/projects/zimage-turbo-pipeline-it.png zimage-turbo-pipeline – pipeline video AI automatica La pipeline recupera notizie recenti, fa scrivere a Gemini prompt per le immagini e testi, genera immagini, musica e voce narrante e con ffmpeg monta un… https://daniele-michelin.com/ports/110/ https://daniele-michelin.com/assets/og/kb/de-p-110.png Port 110: POP3 mit STARTTLS · Daniele Michelin Port 110 für POP3: Mails abholen mit STARTTLS, warum Port 995 mit implizitem TLS vorzuziehen ist und wann Sie Port 110 ganz schließen können. https://daniele-michelin.com/ports/11211/ https://daniele-michelin.com/assets/og/kb/de-p-11211.png Port 11211: Memcached nur lokal · Daniele Michelin Port 11211 für Memcached: der Cache hinter PHP-Apps. Warum UDP 11211 für Rekord-DDoS missbraucht wurde und wie Sie Memcached absichern. https://daniele-michelin.com/ports/1194/ https://daniele-michelin.com/assets/og/kb/de-p-1194.png Port 1194: OpenVPN über UDP · Daniele Michelin Port 1194 für OpenVPN: Standard ist UDP, TCP und Port 443 als Ausweichlösung. Firewall-Regeln, MTU-Probleme und der Vergleich mit WireGuard. https://daniele-michelin.com/ports/123/ https://daniele-michelin.com/assets/og/kb/de-p-123.png Port 123: NTP-Zeitsynchronisation · Daniele Michelin Port 123/UDP für NTP: warum exakte Zeit für TLS, Kerberos und 2FA zählt, ob der Port offen sein muss und wie Sie die Synchronisation prüfen. https://daniele-michelin.com/ports/143/ https://daniele-michelin.com/assets/og/kb/de-p-143.png Port 143: IMAP mit STARTTLS · Daniele Michelin Port 143 für IMAP: Postfachzugriff mit STARTTLS, Unterschied zu Port 993, und warum Sie Klartext-Logins auf Port 143 unterbinden sollten. https://daniele-michelin.com/ports/20-21/ https://daniele-michelin.com/assets/og/kb/de-p-20-21.png Port 20/21: FTP und seine Firewall-Tücken · Daniele Michelin Port 21 ist der FTP-Steuerkanal, Port 20 der Datenkanal im Active Mode. Warum FTP Passive-Ports braucht und wann SFTP die bessere Wahl ist. https://daniele-michelin.com/ports/2049/ https://daniele-michelin.com/assets/og/kb/de-p-2049.png Port 2049: NFS-Freigaben im LAN · Daniele Michelin Port 2049 für NFS: NFSv4 braucht nur diesen Port, NFSv3 zusätzlich rpcbind und mountd. Firewall-Regeln, Rechteprobleme und Sicherheit. https://daniele-michelin.com/ports/22/ https://daniele-michelin.com/assets/og/kb/de-p-22.png Port 22: SSH und SFTP absichern · Daniele Michelin Port 22 für SSH und SFTP: Was dort läuft, wie Sie den Zugang mit Schlüsseln, Fail2ban und IP-Filter härten und typische Login-Fehler lösen. https://daniele-michelin.com/ports/25/ https://daniele-michelin.com/assets/og/kb/de-p-25.png Port 25: SMTP zwischen Mailservern · Daniele Michelin Port 25 ist für den Mailtransport zwischen Servern (MX), nicht für Mailclients. Warum Provider Port 25 sperren und wie Sie STARTTLS testen. https://daniele-michelin.com/ports/3306/ https://daniele-michelin.com/assets/og/kb/de-p-3306.png Port 3306: MySQL und MariaDB · Daniele Michelin Port 3306 für MySQL und MariaDB: warum die Datenbank nicht öffentlich sein sollte, bind-address, SSH-Tunnel und typische Verbindungsfehler. https://daniele-michelin.com/ports/3389/ https://daniele-michelin.com/assets/og/kb/de-p-3389.png Port 3389: RDP sicher betreiben · Daniele Michelin Port 3389 für Remote Desktop (RDP): warum er nie direkt im Internet stehen sollte, NLA, VPN oder RD Gateway und typische Verbindungsfehler. https://daniele-michelin.com/ports/3478/ https://daniele-michelin.com/assets/og/kb/de-p-3478.png Port 3478: STUN/TURN für Nextcloud Talk · Daniele Michelin Port 3478 für STUN/TURN mit coturn: so funktionieren Nextcloud Talk Anrufe hinter NAT. Firewall, Relay-Ports, external-ip und typische Fehler. https://daniele-michelin.com/ports/389/ https://daniele-michelin.com/assets/og/kb/de-p-389.png Port 389: LDAP und StartTLS · Daniele Michelin Port 389 für LDAP und Active Directory: Verzeichniszugriff mit StartTLS, warum der Port nie ins Internet gehört und typische Bind-Fehler. https://daniele-michelin.com/ports/4190/ https://daniele-michelin.com/assets/og/kb/de-p-4190.png Port 4190: ManageSieve für Mailfilter · Daniele Michelin Port 4190 für ManageSieve: serverseitige Mailfilter und Abwesenheitsnotizen per Sieve verwalten, für Roundcube, Thunderbird und Nextcloud Mail. https://daniele-michelin.com/ports/443/ https://daniele-michelin.com/assets/og/kb/de-p-443.png Port 443: HTTPS, TLS und HTTP/3 · Daniele Michelin Port 443 für HTTPS: TCP für TLS, UDP für HTTP/3 (QUIC). So prüfen Sie Zertifikatskette und SNI und beheben typische TLS-Fehler am Webserver. https://daniele-michelin.com/ports/465/ https://daniele-michelin.com/assets/og/kb/de-p-465.png Port 465: SMTPS mit implizitem TLS · Daniele Michelin Port 465 für den Mailversand mit implizitem TLS: seit RFC 8314 wieder Standard. Unterschied zu Port 587 und typische Einstellungsfehler. https://daniele-michelin.com/ports/51820/ https://daniele-michelin.com/assets/og/kb/de-p-51820.png Port 51820: WireGuard-VPN einrichten · Daniele Michelin Port 51820/UDP für WireGuard: der übliche ListenPort, warum Portscans nichts zeigen, und wie Sie Handshake-, NAT- und MTU-Probleme lösen. https://daniele-michelin.com/ports/53/ https://daniele-michelin.com/assets/og/kb/de-p-53.png Port 53: DNS über UDP und TCP · Daniele Michelin Port 53 für DNS: warum neben UDP auch TCP offen sein muss, wann der Port öffentlich sein darf und wie offene Resolver missbraucht werden. https://daniele-michelin.com/ports/5432/ https://daniele-michelin.com/assets/og/kb/de-p-5432.png Port 5432: PostgreSQL absichern · Daniele Michelin Port 5432 für PostgreSQL: listen_addresses, pg_hba.conf und warum die Datenbank nicht öffentlich sein sollte. Typische Verbindungsfehler lösen. https://daniele-michelin.com/ports/587/ https://daniele-michelin.com/assets/og/kb/de-p-587.png Port 587: SMTP-Submission mit STARTTLS · Daniele Michelin Port 587 für den Mailversand aus Clients: Submission mit STARTTLS und Pflicht-Login. Port 587 oder 465? Unterschiede und typische Fehler. https://daniele-michelin.com/ports/636/ https://daniele-michelin.com/assets/og/kb/de-p-636.png Port 636: LDAPS mit implizitem TLS · Daniele Michelin Port 636 für LDAPS: LDAP mit implizitem TLS für Nextcloud, Mail und AD. Zertifikatsprobleme lösen und den Zugriff korrekt einschränken. https://daniele-michelin.com/ports/6379/ https://daniele-michelin.com/assets/og/kb/de-p-6379.png Port 6379: Redis nie öffentlich · Daniele Michelin Port 6379 für Redis: warum offene Redis-Instanzen gekapert werden, protected-mode, Passwort, Unix-Socket und Redis als Nextcloud-Cache. https://daniele-michelin.com/ports/80/ https://daniele-michelin.com/assets/og/kb/de-p-80.png Port 80: HTTP, Redirect und ACME · Daniele Michelin Port 80 für HTTP: warum er trotz HTTPS offen bleiben sollte, wie Let's Encrypt HTTP-01 ihn nutzt und welche Redirect-Fehler typisch sind. https://daniele-michelin.com/ports/8080/ https://daniele-michelin.com/assets/og/kb/de-p-8080.png Port 8080: alternativer HTTP-Port · Daniele Michelin Port 8080 als alternativer HTTP-Port für Proxys, Tomcat, Docker-Container und Backends. Warum er nicht öffentlich sein sollte und die Docker-Falle. https://daniele-michelin.com/ports/8443/ https://daniele-michelin.com/assets/og/kb/de-p-8443.png Port 8443: alternatives HTTPS und Plesk · Daniele Michelin Port 8443 als alternativer HTTPS-Port: Plesk-Panel, Tomcat, UniFi und Admin-Oberflächen. Wie Sie den Zugriff einschränken und Fehler lösen. https://daniele-michelin.com/ports/853/ https://daniele-michelin.com/assets/og/kb/de-p-853.png Port 853: verschlüsseltes DNS mit DoT · Daniele Michelin Port 853 für DNS over TLS und DNS over QUIC: verschlüsselte DNS-Anfragen, Android Private DNS, Firewall-Regeln und Unterschiede zu DoH. https://daniele-michelin.com/ports/9000/ https://daniele-michelin.com/assets/og/kb/de-p-9000.png Port 9000: PHP-FPM und FastCGI · Daniele Michelin Port 9000 für PHP-FPM: FastCGI zwischen nginx und PHP, warum ein offener Port 9000 Codeausführung erlaubt und wie Sie 502-Fehler beheben. https://daniele-michelin.com/ports/9090/ https://daniele-michelin.com/assets/og/kb/de-p-9090.png Port 9090: Prometheus-Server und Cockpit · Daniele Michelin Port 9090 für den Prometheus-Server: Web-UI und API ohne eingebaute Anmeldung. Auch Cockpit nutzt 9090. Absicherung und Fehlersuche. https://daniele-michelin.com/ports/9100/ https://daniele-michelin.com/assets/og/kb/de-p-9100.png Port 9100: node_exporter für Prometheus · Daniele Michelin Port 9100 für den Prometheus node_exporter: Systemmetriken für Monitoring. Warum der Port nur für den Prometheus-Server offen sein sollte. https://daniele-michelin.com/ports/993/ https://daniele-michelin.com/assets/og/kb/de-p-993.png Port 993: IMAPS mit implizitem TLS · Daniele Michelin Port 993 für IMAPS: Postfachzugriff mit implizitem TLS, die empfohlene Einstellung für Mailclients. Zertifikats- und Login-Probleme lösen. https://daniele-michelin.com/ports/995/ https://daniele-michelin.com/assets/og/kb/de-p-995.png Port 995: POP3S mit implizitem TLS · Daniele Michelin Port 995 für POP3S: Mails mit implizitem TLS abholen. Wann POP3 noch sinnvoll ist, wie Sie den Port absichern und warum Mails verschwinden. https://daniele-michelin.com/ports/ https://daniele-michelin.com/assets/og/kb/de-hub-ports.png Netzwerk-Ports für Admins: Liste mit Erklärung · Daniele Michelin Die wichtigsten TCP/UDP-Ports für Mail, Web, DNS, Datenbanken und VPN: was darauf läuft, ob er offen sein sollte und wie man ihn prüft. https://daniele-michelin.com/projekte/acestudio-mac/ https://daniele-michelin.com/assets/og/projects/acestudio-mac-de.png ACE Studio – Native macOS-App für lokale KI-Musik ACE Studio ist eine SwiftUI-Oberfläche für eine lokale ACE-Step-1.5-Installation: Man beschreibt einen Song, die App schreibt Text und Stil, steuert die… https://daniele-michelin.com/projekte/ai-receptionist/ https://daniele-michelin.com/assets/og/projects/ai-receptionist-de.png Local AI Receptionist – KI-Telefon-Receptionist, komplett lokal Ein KI-Receptionist, der ans Telefon geht (Twilio-Nummer) oder im Browser antwortet, Termine vereinbart und Italienisch (mit Mailänder Akzent) und Deutsch… https://daniele-michelin.com/projekte/famiglia-os/ https://daniele-michelin.com/assets/og/projects/famiglia-os-de.png FamigliaOS – Das digitale Zuhause, self-hosted FamigliaOS soll Kalender, Aufgaben, Essensplanung und mehr für die ganze Familie an einem Ort bündeln – als selbst gehostete App in einem einzigen Container. https://daniele-michelin.com/projekte/jarvis/ https://daniele-michelin.com/assets/og/projects/jarvis-de.png J.A.R.V.I.S. – KI-Assistent für macOS mit 120+ Tools J.A.R.V.I.S. ist ein KI-Assistent im Cyberpunk-Look für macOS: Python/FastAPI-Backend, Vite/TypeScript-Frontend, Eingabe per Text, Sprache und Bild. Alle… https://daniele-michelin.com/projekte/job-hunter/ https://daniele-michelin.com/assets/og/projects/job-hunter-de.png job-hunter – Self-hosted Jobsuche-Assistent · Daniele Michelin job-hunter sucht jeden Morgen neue Stellen, bewertet sie anhand des eigenen Profils und schreibt mit KI ein kurzes deutsches Anschreiben. https://daniele-michelin.com/projekte/llm-wiki/ https://daniele-michelin.com/assets/og/projects/llm-wiki-de.png LLM-Wiki – RAG-System für eigene Dokumente · Daniele Michelin LLM-Wiki ist ein RAG-System für eigene Dokumente: Man stellt Fragen per Text oder Sprache und bekommt Antworten, die jeweils mit den verwendeten Quellen… https://daniele-michelin.com/projekte/zimage-turbo-pipeline/ https://daniele-michelin.com/assets/og/projects/zimage-turbo-pipeline-de.png zimage-turbo-pipeline – automatische KI-Video-Pipeline Die Pipeline holt aktuelle Nachrichten, lässt Gemini Bild-Prompts und Texte schreiben, erzeugt Bilder, Musik und Sprecherstimme und setzt daraus mit ffmpeg… https://daniele-michelin.com/spickzettel/dig-befehle/ https://daniele-michelin.com/assets/og/kb/de-c-dig.png dig Befehle – DNS Cheat Sheet für die Praxis · Daniele Michelin dig Befehle für DNS-Diagnose: A, MX, TXT, CAA, +short, +trace, Reverse Lookup, DNSSEC, SPF/DKIM/DMARC prüfen und autoritative Nameserver abfragen. https://daniele-michelin.com/spickzettel/docker-befehle/ https://daniele-michelin.com/assets/og/kb/de-c-docker.png Docker Befehle – Cheat Sheet für Admins · Daniele Michelin Die wichtigsten Docker Befehle: Images, Container, Logs, exec, Volumes, Netzwerke, Compose, aufräumen mit prune und Ressourcen-Limits. https://daniele-michelin.com/spickzettel/git-befehle/ https://daniele-michelin.com/assets/og/kb/de-c-git.png Git Befehle – Cheat Sheet für Alltag & Rettung · Daniele Michelin Die wichtigsten Git Befehle: Status, Log, Stash, Rebase, Reflog-Rettung, Undo-Varianten, Remotes und Bisect für den Alltag. https://daniele-michelin.com/spickzettel/ https://daniele-michelin.com/assets/og/kb/de-hub-cheats.png Spickzettel für Admins: nginx, Docker, Git, systemd u. a. Durchsuchbare Befehlsübersichten für Nextcloud occ, dig, journalctl, openssl, nginx, systemctl, Docker und Git — mit Kopier-Knopf und Hinweisen auf riskante Befehle. https://daniele-michelin.com/spickzettel/journalctl-befehle/ https://daniele-michelin.com/assets/og/kb/de-c-journalctl.png journalctl Befehle – Cheat Sheet für Linux · Daniele Michelin journalctl Befehle für die Fehlersuche: Logs nach Unit, Boot, Zeit und Priorität filtern, live folgen, JSON-Ausgabe und Journal-Größe begrenzen. https://daniele-michelin.com/spickzettel/nextcloud-occ-befehle/ https://daniele-michelin.com/assets/og/kb/de-c-occ.png Nextcloud occ Befehle – Cheat Sheet für Admins · Daniele Michelin Die wichtigsten Nextcloud occ Befehle für Admins: Wartungsmodus, files:scan, Benutzer, Apps, Datenbank-Indizes, Cron, Papierkorb und 2FA. https://daniele-michelin.com/spickzettel/nginx-befehle/ https://daniele-michelin.com/assets/og/kb/de-c-nginx.png nginx Befehle – Cheat Sheet für Admins · Daniele Michelin Die wichtigsten nginx Befehle für Admins: Konfig testen, Reload, Logs, Redirects, proxy_pass, Rate Limiting, gzip und Fehlersuche im Betrieb. https://daniele-michelin.com/spickzettel/openssl-befehle/ https://daniele-michelin.com/assets/og/kb/de-c-openssl.png OpenSSL Befehle – Cheat Sheet für TLS & Zertifikate · Daniele Michelin OpenSSL Befehle für TLS-Diagnose: Zertifikatskette und Ablauf prüfen, CSR erstellen, Key/Zertifikat abgleichen, PEM/DER/PFX umwandeln, STARTTLS. https://daniele-michelin.com/spickzettel/systemctl-befehle/ https://daniele-michelin.com/assets/og/kb/de-c-systemctl.png systemctl Befehle – systemd Cheat Sheet · Daniele Michelin Die wichtigsten systemctl Befehle: Status, start, restart, enable, Timer, Drop-in-Overrides, systemd-analyze und Targets für Admins. https://daniele-michelin.com/vergleich/http-01-vs-dns-01/ https://daniele-michelin.com/assets/og/kb/de-v-http-01-vs-dns-01.png Let's Encrypt: HTTP-01 vs. DNS-01 · Daniele Michelin HTTP-01 oder DNS-01 Challenge für Let's Encrypt? Wildcards, interne Hosts, Port 80, DNS-API-Zugang und typische Fehler bei der Validierung im Vergleich. https://daniele-michelin.com/vergleich/ https://daniele-michelin.com/assets/og/kb/de-hub-compare.png Technik-Vergleiche für Admins: SAML, Nextcloud, DNS · Daniele Michelin Ehrliche Vergleiche aus dem Betrieb: SAML oder OIDC, Nextcloud oder Seafile, HTTP-01 oder DNS-01, cron oder systemd-Timer — wann welche Lösung passt. https://daniele-michelin.com/vergleich/nextcloud-aio-vs-manuelle-installation/ https://daniele-michelin.com/assets/og/kb/de-v-nextcloud-aio-vs-manual.png Nextcloud AIO vs. manuelle Installation · Daniele Michelin Nextcloud All-in-One oder klassisch mit Webserver, PHP-FPM und Datenbank? Aufwand, Kontrolle, Updates, Backup und Fehlersuche ehrlich verglichen. https://daniele-michelin.com/vergleich/nextcloud-s3-vs-nfs/ https://daniele-michelin.com/assets/og/kb/de-v-s3-vs-nfs-nextcloud.png Nextcloud: S3 vs. NFS als Primärspeicher · Daniele Michelin S3-Objektspeicher oder NFS bzw. Block Storage als Nextcloud-Primärspeicher? Datenformat, Skalierung, Backup, Migration und Fallstricke aus dem Betrieb. https://daniele-michelin.com/vergleich/nextcloud-vs-seafile/ https://daniele-michelin.com/assets/og/kb/de-v-nextcloud-vs-seafile.png Nextcloud vs. Seafile: Vergleich · Daniele Michelin Nextcloud oder Seafile selbst hosten? Speicherformat, Sync, Funktionsumfang, Updates und Backup im Vergleich – nüchtern aus der Sicht des Betriebs. https://daniele-michelin.com/vergleich/nginx-vs-apache-php-fpm/ https://daniele-michelin.com/assets/og/kb/de-v-nginx-vs-apache-php.png nginx vs. Apache für PHP-Apps · Daniele Michelin nginx oder Apache vor PHP-FPM? .htaccess, Konfiguration, Upload-Limits, Timeouts und Fehlersuche für Nextcloud, WordPress und andere PHP-Apps. https://daniele-michelin.com/vergleich/saml-vs-oidc/ https://daniele-michelin.com/assets/og/kb/de-v-saml-vs-oidc.png SAML vs. OIDC: Was passt wann? · Daniele Michelin SAML oder OpenID Connect für Single Sign-on? Unterschiede bei Protokoll, Clients, Zertifikaten und Fehlersuche, aus dem Betrieb mit Nextcloud und Keycloak. https://daniele-michelin.com/vergleich/spf-dkim-dmarc-unterschied/ https://daniele-michelin.com/assets/og/kb/de-v-spf-dkim-dmarc.png SPF vs. DKIM vs. DMARC: Vergleichstabelle · Daniele Michelin Was SPF, DKIM und DMARC jeweils prüfen, wo sie versagen und warum Sie alle drei brauchen. Mit Alignment, Weiterleitungen und typischen Fehlern. https://daniele-michelin.com/vergleich/systemd-timer-vs-cron/ https://daniele-michelin.com/assets/og/kb/de-v-systemd-timer-vs-cron.png systemd-Timer vs. Cron: Vergleich · Daniele Michelin systemd-Timer oder Cron für geplante Aufgaben? Logging, verpasste Läufe, Überlappung, Umgebung und Aufwand im Vergleich, mit Beispielen aus dem Alltag.