Port 9090: Prometheus server and Cockpit

Port 9090 is the default port of the Prometheus server and, on RHEL/Fedora, of the Cockpit web console.

Port: 9090
Protocol: TCP
Service: Prometheus / Cockpit
Exposure: Public: no, internal or behind a proxy

daniele@mikweb: ~/ports — less 9090.md

Port 9090 serves the Prometheus web UI and HTTP API. On RHEL, Fedora and Debian systems with Cockpit, the web console cockpit.socket also uses 9090 – check what's listening before installing.

Not public. Without web.config.file Prometheus has neither login nor TLS; anyone can read all metrics and run queries via the API. Put it behind a reverse proxy with authentication, or keep it internal or VPN-only.

Typical: targets shown as DOWN with context deadline exceeded – usually a firewall on the target host blocks the exporter port (e.g. 9100).

Check

curl -s http://localhost:9090/-/healthy