#operations

Docker port is already allocated: Finding and Freeing the Taken Port

docker run fails with port is already allocated or bind: address already in use? The host-side port you mapped is taken — by another container's docker-proxy or a host process. How to tell the two apart, the compose project-name collision scenario, and why 127.0.0.1 and a specific IP binding can coexist.

Docker no space left on device: the Complete Cleanup Ladder, Safe to Aggressive

Docker build or run failing with no space left on device? Dangling images, stopped containers, build cache, and unbounded container logs — see exactly who eats the disk with docker system df. The prune ladder from container prune to system prune -a, the --volumes danger zone, and the log-rotation config that stops it coming back.

Cannot connect to the Docker daemon — 5 Reasons and How to Diagnose Each

docker ps fails with Cannot connect to the Docker daemon at unix:///var/run/docker.sock? Covers the Linux service not running, Docker Desktop not started, WSL2 integration reset, daemon.json syntax errors killing the daemon, wrong docker context, and missing rootless DOCKER_HOST — with journalctl diagnostics.