docker

Docker Skill

OS-level virtualization to deliver software in packages called containers.

Ecosystem Graph

graph LR
  docker["Docker"]
  docker -- "deploys to" --> kubernetes
  docker -- "integrates with" --> github-actions

Quick Start

Docker packages your application and its dependencies into an immutable image, ensuring 'it works on my machine' scales to production.

docker build -t my-app .
docker run -p 8080:8080 my-app

Production Patterns

Multi-Stage Builds

Never ship build tools (like compilers or dev dependencies) in your final production image. Use a build stage to compile your code, then copy only the compiled artifacts into a distroless or alpine base image for the final stage.

Architecture & Scaling

Image Caching

Docker builds images in layers. Order your Dockerfile from least frequently changed (OS dependencies, package managers) to most frequently changed (source code). This ensures Docker caches the heavy steps and dramatically speeds up CI pipelines.

Error Recovery

Use a process manager like PM2 or tini as PID 1 inside your container to properly handle OS signals (SIGTERM/SIGINT) and reap zombie processes, allowing graceful shutdowns.

Security Notes

Never run your container as the root user. Explicitly create and switch to a non-root USER at the end of your Dockerfile. Scan your images using tools like Trivy or Docker Scout to catch CVEs before deployment.

Relationships

Works Well With: github-actions

Deploys To: kubernetes

References

• Docker Docs

Why use this skill

Use this when your agent works with docker — structured patterns beat pasted docs and prevent common hallucinations.

AI pitfalls

• Referencing CLI flags or config keys that do not exist
• Using outdated major versions of tools
• Skipping lockfile or version pinning in examples

Production checklist

• Secrets in environment variables, not source code
• Error handling and logging in place
• Rate limits and timeouts configured