~/blog / topic / linux
Linux troubleshooting: services, logs, disk, SSH
Short, verifiable paths through typical Linux problems: services, logs, disk space, access and network. With commands I use in support myself.
A school report card for your website: security headers, e-mail protection and certificate, graded like at school
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.
We graded the security headers of 57 big websites: only 21 ship an effective CSP
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.
HTTP security headers in ten minutes: a safe starter set for nginx and how to test it
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.
Nextcloud doesn't show copied files: file system, database and 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.
Incident note: No space left on device despite free space
No space left on device, but df shows free space? Usually the inodes are exhausted or deleted files are still open. Diagnose with df -i and lsof +L1.
One week after PHP2Shell: attacked in the wild, and now a Linux kernel flaw on top
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.
Root cause analysis in support: why the cause rarely sits where the symptom shows
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.
Nextcloud: Collabora's built-in CODE server is being exploited. Check it today
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.
Three critical NGINX flaws: less dramatic than PHP2Shell, but patch them quickly anyway
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.
PHP emergency patch (PHP2Shell): how to check and patch your 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.
Topics: Nextcloud DNS, mail & certificates AI, LLMs & RAG Security & patches