Docker & Containerization

When to use this skill

• Creating Dockerfile or docker-compose.yml.
• Optimizing image size.
• Debugging container networking.

1. Dockerfile Best Practices

• Multi-Stage: Use multi-stage builds to keep production images small (e.g., build in node:20, run in node:20-alpine).
• Ordering: Place frequent changes (code copying) AFTER infrequent changes (npm install) to leverage layer caching.
• User: Don't run as root. User USER node or create a non-root user.

2. Docker Compose

• Services: Define services clearly (app, db, redis).
• Volumes: Use named volumes for persistence (postgres_data:/var/lib/postgresql/data).
• Env: Use .env file for environment variables.