Docker Complete Guide: Images, Containers, Volumes & Compose

# === IMAGES ===
docker pull nginx:latest           # Download image from Docker Hub
docker images                      # List local images
docker image inspect nginx         # Detailed image info
docker rmi nginx:latest            # Remove image
docker build -t myapp:1.0 .        # Build image from Dockerfile
docker tag myapp:1.0 myrepo/myapp:1.0  # Tag for pushing

# === CONTAINERS ===
docker run nginx                   # Run container (foreground)
docker run -d nginx                # Run detached (background)
docker run -d -p 8080:80 nginx     # Map port host:container
docker run -d --name my-nginx nginx  # Named container
docker run --rm nginx              # Auto-remove when stopped

docker ps                          # Running containers
docker ps -a                       # All containers (including stopped)
docker stop my-nginx               # Graceful stop
docker start my-nginx              # Start stopped container
docker restart my-nginx            # Restart
docker rm my-nginx                 # Remove container
docker rm -f my-nginx              # Force remove (even if running)

# === INTERACT WITH CONTAINER ===
docker exec -it my-nginx bash      # Open bash shell in container
docker exec -it my-nginx sh        # Use sh if bash not available
docker logs my-nginx               # View container logs
docker logs -f my-nginx            # Follow logs in real-time
docker inspect my-nginx            # Detailed container config/state
docker stats                       # Live resource usage stats
docker cp my-nginx:/etc/nginx.conf ./nginx.conf  # Copy file from container

# === CLEANUP ===
docker system prune                # Remove all unused data
docker system prune -a             # Remove all unused images too
docker volume prune                # Remove unused volumes

# Stage 1: Build
FROM node:20-alpine AS builder

# Set working directory
WORKDIR /app

# Copy dependency files first (cache optimization!)
COPY package*.json ./

# Install dependencies
RUN npm ci --only=production

# Copy application source
COPY . .

# Build the app
RUN npm run build

# ─────────────────────────────────────────────
# Stage 2: Production (smaller final image)
FROM node:20-alpine AS production

WORKDIR /app

# Create non-root user for security
RUN addgroup -S appgroup && adduser -S appuser -G appgroup

# Copy only production artifacts
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY package.json .

# Set correct ownership
RUN chown -R appuser:appgroup /app

# Switch to non-root user
USER appuser

# Expose port
EXPOSE 3000

# Health check
HEALTHCHECK --interval=30s --timeout=3s --start-period=10s \
  CMD node healthcheck.js || exit 1

# Start application
CMD ["node", "dist/server.js"]

# Named volumes (managed by Docker)
docker volume create mydata
docker run -v mydata:/var/lib/postgresql/data postgres

# Bind mounts (host path → container path)
docker run -v /host/path:/container/path nginx
docker run -v $(pwd)/nginx.conf:/etc/nginx/nginx.conf:ro nginx  # Read-only

# Anonymous volumes (avoid — hard to manage)
docker run -v /var/lib/mysql mysql

# Volume commands
docker volume ls                   # List volumes
docker volume inspect mydata       # Volume details
docker volume rm mydata            # Remove volume
docker volume prune                # Remove unused volumes

version: '3.8'

services:
  # Nginx reverse proxy
  nginx:
    image: nginx:alpine
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro
      - ./certbot/conf:/etc/letsencrypt
    depends_on:
      - app
    restart: unless-stopped

  # Node.js application
  app:
    build:
      context: .
      dockerfile: Dockerfile
      target: production
    environment:
      - NODE_ENV=production
      - DATABASE_URL=postgresql://user:pass@postgres:5432/mydb
      - REDIS_URL=redis://redis:6379
    depends_on:
      postgres:
        condition: service_healthy
      redis:
        condition: service_started
    restart: unless-stopped

  # PostgreSQL database
  postgres:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: mydb
    volumes:
      - postgres_data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U user -d mydb"]
      interval: 10s
      timeout: 5s
      retries: 5

  # Redis cache
  redis:
    image: redis:7-alpine
    command: redis-server --appendonly yes
    volumes:
      - redis_data:/data

volumes:
  postgres_data:
  redis_data:

networks:
  default:
    name: myapp-network

docker-compose up -d               # Start all services (detached)
docker-compose up --build          # Rebuild images before starting
docker-compose down                # Stop and remove containers
docker-compose down -v             # Also remove volumes
docker-compose logs -f app         # Follow logs for app service
docker-compose exec app sh         # Shell into app container
docker-compose ps                  # Status of all services
docker-compose restart nginx       # Restart specific service
docker-compose scale app=3         # Scale app to 3 instances