# Docker

> Docker and containerization best practices including multi-stage builds, security, and Docker Compose.

- Skill: `diegosouzapw/docker` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add diegosouzapw/docker`
- Raw SKILL.md: https://api.skillmd.com/api/skills/diegosouzapw/docker/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: diegosouzapw (https://skillmd.com/u/diegosouzapw)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/diegosouzapw/docker

---


# Docker Best Practices

## Dockerfile
- Use specific base image tags (not :latest)
- Use multi-stage builds for smaller images
- Minimize layers (combine RUN commands)
- Copy package.json first for caching
- Run as non-root user
- Use .dockerignore

## Example Multi-stage Build
```dockerfile
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM node:20-alpine AS runner
WORKDIR /app
RUN addgroup -g 1001 nodejs
RUN adduser -S nodejs -u 1001
COPY --from=builder /app/dist ./dist
USER nodejs
CMD ["node", "dist/index.js"]
```

## Docker Compose
- Use version 3.8+
- Define healthchecks
- Use named volumes for persistence
- Configure restart policies
- Use environment files

## Security
- Scan images for vulnerabilities
- Don't run as root
- Use secrets for sensitive data
- Keep base images updated
- Use distroless/alpine images

## Performance
- Use BuildKit
- Leverage layer caching
- Use .dockerignore
- Minimize image size