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Docker Exec Cheat Sheet

Run commands inside running containers for debugging, inspection, and quick maintenance tasks.

What this cheat sheet is for

This docker exec reference helps you complete common developer tasks quickly and avoid repeated trial-and-error when working under deadlines.

  • When you need a reliable command or pattern during debugging and incident response.
  • When you are implementing a feature and want a known-good syntax example immediately.
  • When onboarding teammates and documenting repeatable workflows for daily use.
  • When reviewing pull requests and verifying that command usage follows best practices.
  • Open a shell in a running app container.
  • Run database migrations inside container context.
  • Inspect filesystem and environment values during incidents.

Interactive shell access

Open bash shell

docker exec -it app bash

Example:

docker exec -it app sh

Run as root user

docker exec -u 0 -it app sh

Example:

docker exec --user www-data app id

Run one-off commands

Check env and process list

docker exec app env

Example:

docker exec app ps aux

Run app command

docker exec app npm run migrate

Example:

docker exec db psql -U postgres -c "SELECT now();"

Copy + verify workflow

Inspect file contents

docker exec app cat /etc/hosts

Example:

docker exec app ls -lah /app

Combine with logs

docker logs app --tail 100

Example:

docker exec app curl -s localhost:3000/health

Common mistakes / Pitfalls

  • docker exec works only on running containers, not stopped ones.
  • Using bash fails on minimal images; use sh when bash is missing.
  • Manual changes inside containers are ephemeral and disappear on rebuild/restart.

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Last updated: February 2026