docker-debugginglisted

# Docker Debugging Find out what the container actually ran, in what environment, and why it stopped. ## Purpose **Use this when:** - A container exits immediately, or restarts repeatedly. - A file that exists in the build is missing at runtime. - The container cannot reach the network, or cannot be reached. - Permission denied on a mounted volume. - It works on one machine and not another. **Do not use this when:** - The container runs under Kubernetes and the symptom is scheduling or probes — use `kubernetes-troubleshooting`. - The question is image quality, size or security — use `container-image-review`. **What this skill assumes:** Docker or a compatible runtime on the host. Commands are shown for `docker`; `podman` and `nerdctl` accept the same arguments for everything used here. ## Operating Procedure 1. **Get the exit code and the reason.** `docker ps -a` and `docker inspect` give both. 2. **Read the logs, including from the exited container.** A stopped container keeps its logs until it is removed. 3. **Establish what actually ran.** The effective entrypoint and command are frequently not what the Dockerfile appears to say. 4. **Compare build-time and run-time.** Most "missing file" reports are a multi-stage build that did not copy it, or a volume mounted over it. 5. **Check the boundaries**: network, mounts, users, and architecture. 6. **Reproduce interactively** with an overridden entrypoint — the fastest way to inspect a broken image. 7. **F