Agent skill
docker
Container optimization, multi-stage builds, Docker Compose, and Docker best practices. Use when writing Dockerfiles, setting up containers, or optimizing image size.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/other/docker-dgkngk-super-kit
SKILL.md
Docker Skill
Overview
Container optimization, multi-stage builds, and Docker best practices.
Multi-Stage Build
# Stage 1: Build
FROM node:20-alpine AS builder
WORKDIR /app
# Install dependencies first (cache layer)
COPY package*.json ./
RUN npm ci
# Build application
COPY . .
RUN npm run build
# Stage 2: Production
FROM node:20-alpine AS production
WORKDIR /app
# Create non-root user
RUN addgroup -g 1001 -S nodejs && \
adduser -S nextjs -u 1001
# Copy only production dependencies
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/package.json ./
# Run as non-root
USER nextjs
# Health check
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
CMD wget --no-verbose --tries=1 --spider http://localhost:3000/health || exit 1
EXPOSE 3000
CMD ["node", "dist/server.js"]
Docker Compose
version: '3.8'
services:
app:
build:
context: .
target: production
ports:
- "3000:3000"
environment:
- NODE_ENV=production
- DATABASE_URL=postgres://db:5432/myapp
depends_on:
db:
condition: service_healthy
restart: unless-stopped
db:
image: postgres:16-alpine
volumes:
- postgres_data:/var/lib/postgresql/data
environment:
POSTGRES_DB: myapp
POSTGRES_USER: user
POSTGRES_PASSWORD_FILE: /run/secrets/db_password
secrets:
- db_password
healthcheck:
test: ["CMD-SHELL", "pg_isready -U user -d myapp"]
interval: 5s
timeout: 5s
retries: 5
redis:
image: redis:7-alpine
volumes:
- redis_data:/data
command: redis-server --appendonly yes
volumes:
postgres_data:
redis_data:
secrets:
db_password:
file: ./secrets/db_password.txt
Best Practices
Image Size Optimization
# Use alpine base
FROM node:20-alpine
# Install only production deps
RUN npm ci --only=production
# Remove unnecessary files
RUN rm -rf /var/cache/apk/*
.dockerignore
node_modules
.git
.gitignore
*.md
.env*
coverage
.nyc_output
dist
Security
- Run as non-root user
- Use secrets for sensitive data
- Scan images:
docker scout cves myimage - Keep base images updated
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