What is docker ps -a in Docker?
docker ps -a (or docker ps --all) lists ALL containers on the system — both running and stopped. Without the -a flag, docker ps only shows currently running containers. It is one of the most frequently used Docker commands for inspecting container state, finding container IDs, and debugging.
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Up X hours/minutes — container is currently running
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Exited (0) — container stopped successfully (exit code 0 = success)
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Exited (1) — container stopped with error (non-zero = failure)
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Exited (137) — container was killed (SIGKILL — often OOM or docker kill)
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Created — container created but never started
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Paused — container is paused (docker pause was called)
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Restarting — container is in restart loop
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Removing — container is being removed
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Dead — container is in a broken state, needs force removal
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docker ps — shows ONLY running containers (STATUS: Up)
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docker ps -a — shows ALL containers regardless of state
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docker ps -q — shows only IDs of running containers
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docker ps -aq — shows only IDs of ALL containers
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docker ps -l — shows the most recently created container
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docker ps -n 5 — shows last 5 created containers
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docker ps -as — shows running containers with disk size info
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docker ps shows only running containers — always use -a to see everything
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The STATUS column is the most important — it tells you exactly why a container stopped
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Exit code 0 = clean stop, non-zero = error — use docker logs to investigate
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Use -q flag to get just IDs — essential for scripting bulk operations
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Use --filter to narrow down containers by status, name, image, or label
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Use --format for clean readable output or JSON for programmatic processing
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docker ps -aq is the foundation of most container cleanup scripts