Error Fix Guides

Common Linux server, Docker, UFW, Nginx, and cron errors — with exact copy-paste fix commands for your stack. No generic advice.

Docker UFW Bypass

Docker traffic bypassing UFW firewall rules via iptables. Containers expose ports to the internet despite UFW deny rules.

Nginx 502 Bad Gateway

Nginx cannot reach the upstream application server. Common causes: app crashed, wrong port, socket path mismatch.

Cron Job Not Running

Scheduled cron jobs silently failing. Causes include missing PATH, wrong user permissions, environment variable issues.

UFW Inactive — Ports Still Open

UFW is disabled but ports remain accessible. iptables rules from Docker or manual rules persist after UFW is stopped.

Permission Denied: Docker Socket

User cannot run Docker commands. /var/run/docker.sock permission denied — user not in docker group.