Docker

Debugging Techniques

• Use docker logs <container> and docker logs --follow for real-time output.
• Use docker exec -it <container> sh to inspect a running container.
• Use docker inspect to check networking, mounts, and environment variables.
• For build failures, use docker build --no-cache to rule out stale layers.
• Use docker stats and docker top for resource monitoring.

Compose Patterns

• Use named volumes for persistent data. Never bind-mount production databases.
• Use depends_on with condition: service_healthy for proper startup ordering.
• Use environment variable files (.env) for configuration, but never commit secrets to version control.
• Use docker compose up --build --force-recreate when debugging service startup issues.

Pitfalls to Avoid

• Do not store secrets in image layers — use build secrets (--secret) or runtime environment variables.
• Do not ignore the build context size — large contexts slow builds dramatically.
• Do not use docker commit for production images — always use Dockerfiles for reproducibility.