Docker¶

# Container lifecycle
docker run -it ubuntu bash          # Run interactive container
docker run -d -p 80:80 nginx        # Run detached with port mapping
docker ps                           # List running containers
docker ps -a                        # List all containers (including stopped)
docker stop container_id            # Graceful stop (SIGTERM)
docker kill container_id            # Force stop (SIGKILL)
docker rm container_id              # Remove stopped container
docker logs -f container_id         # Follow container logs

# Image management
docker images                       # List local images
docker pull nginx:latest            # Download image
docker build -t myapp:1.0 .         # Build from Dockerfile
docker tag myapp:1.0 user/myapp:1.0 # Tag image
docker push user/myapp:1.0          # Push to registry
docker rmi image_id                 # Remove image
docker image prune                  # Remove unused images

# Inspection and debugging
docker exec -it container_id bash   # Execute command in running container
docker inspect container_id         # JSON details about container
docker logs container_id            # View container logs
docker stats                        # Real-time resource usage
docker top container_id             # Running processes in container

# Cleanup
docker system prune                 # Remove unused data (images, containers, networks)
docker system prune -a              # Remove ALL unused images (not just dangling)
docker volume prune                 # Remove unused volumes (careful!)

# Docker Compose (multi-container apps)
docker compose up -d                # Start services in background
docker compose down                 # Stop and remove containers
docker compose logs -f              # Follow logs from all services
docker compose ps                   # List running services
docker compose restart service_name # Restart specific service

# Dockerfile best practices (multi-stage build)
# Stage 1: Build
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production  # (1)!
COPY . .
RUN npm run build

# Stage 2: Production
FROM node:20-alpine
WORKDIR /app

# Create non-root user
RUN addgroup -g 1001 -S nodejs && \
    adduser -S nodejs -u 1001  # (2)!

# Copy artifacts from builder
COPY --from=builder --chown=nodejs:nodejs /app/dist ./dist
COPY --from=builder --chown=nodejs:nodejs /app/node_modules ./node_modules
COPY --from=builder --chown=nodejs:nodejs /app/package.json ./

# Switch to non-root user
USER nodejs  # (3)!

# Health check
HEALTHCHECK --interval=30s --timeout=3s \
  CMD node healthcheck.js || exit 1  # (4)!

EXPOSE 3000
CMD ["node", "dist/server.js"]

# docker-compose.yml (realistic production-ish setup)
version: '3.8'

services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      NODE_ENV: production
      DATABASE_URL: postgres://postgres:password@db:5432/myapp  # (1)!
    depends_on:
      db:
        condition: service_healthy  # (2)!
    restart: unless-stopped  # (3)!
    volumes:
      - ./logs:/app/logs  # Persist logs
    networks:
      - app-network
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]
      interval: 30s
      timeout: 10s
      retries: 3

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: myapp
      POSTGRES_PASSWORD: password  # (4)!
    volumes:
      - postgres-data:/var/lib/postgresql/data  # (5)!
    networks:
      - app-network
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 10s
      timeout: 5s
      retries: 5

  redis:
    image: redis:7-alpine
    command: redis-server --appendonly yes  # (6)!
    volumes:
      - redis-data:/data
    networks:
      - app-network

volumes:
  postgres-data:  # Named volume (persists data)
  redis-data:

networks:
  app-network:
    driver: bridge