Docker Series Part 5: Debugging, Logs, and Best Practices

Table of Contents

Docker Series Part 5: Debugging, Logs, and Best Practices

Now that you have a solid workflow with Docker Compose, volumes, and environment variables, let’s look at how to debug your containers, view logs, and follow some best practices for smoother development.

Viewing Logs

To see the output from your containers, use:

docker compose logs

Or for a specific service:

docker compose logs web

Add -f to follow logs in real time:

docker compose logs -f

Debugging Containers

Sometimes you need to get inside a running container to inspect files or run commands. Use:

docker compose exec web sh

This opens a shell inside the web service container.

Common Issues & Solutions

  • Port conflicts: Make sure the ports you expose aren’t already in use on your host.
  • File permissions: When using volumes, permissions may differ between host and container. Adjust with chown or Dockerfile USER instructions if needed.
  • Dependency issues: Always rebuild your image (docker compose build) if you change dependencies.

Best Practices

  • Use .dockerignore to avoid copying unnecessary files into your image.
  • Keep images small by using slim or alpine base images.
  • Pin dependency versions in requirements.txt for reproducible builds.
  • Use environment variables for configuration, not hardcoded values.
  • Clean up unused containers and images regularly with:
    docker system prune

Recap

  • Use docker compose logs and exec for troubleshooting.
  • Follow best practices for efficient, maintainable Docker projects.

This wraps up the basics of Docker for development! Explore more advanced topics like CI/CD integration, multi-stage builds, and security as you grow.