Docker

# Run a container
docker run <image>
docker run -d <image>           # Detached mode
docker run -p 8080:80 <image>   # Port mapping
docker run --name myapp <image> # Named container
docker run -it <image> bash     # Interactive shell

# Manage containers
docker ps                  # List running
docker ps -a               # List all
docker stop <container>    # Stop
docker start <container>   # Start
docker rm <container>      # Remove
docker logs <container>    # View logs

# Pull an image
docker pull <image>:<tag>

# Build from Dockerfile
docker build -t myapp:latest .
docker build -f Dockerfile.prod -t myapp:prod .

# List and remove images
docker images
docker rmi <image>
docker image prune     # Remove unused

# Multi-stage build — keeps final image small
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Runtime stage — only what ships to production
FROM node:20-alpine AS runtime
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
EXPOSE 3000
CMD ["node", "dist/server.js"]

services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      DATABASE_URL: postgres://db:5432/app
    depends_on:
      db:
        condition: service_healthy

  db:
    image: postgres:16-alpine
    volumes:
      - pgdata:/var/lib/postgresql/data
    environment:
      POSTGRES_DB: app
      POSTGRES_PASSWORD: secret
    healthcheck:
      test: ["CMD", "pg_isready", "-U", "postgres"]
      interval: 5s
      retries: 5

volumes:
  pgdata:

# Networks
docker network create mynet
docker network ls
docker run --network mynet <image>

# Volumes
docker volume create mydata
docker volume ls
docker run -v mydata:/app/data <image>
docker run -v $(pwd):/app <image>  # Bind mount

# Inspect container details
docker inspect <id>
docker inspect <id> --format '{{.State.Status}}'

# Live resource stats
docker stats

# Exec into running container
docker exec -it <id> sh
docker exec <id> cat /app/config.json

# Copy files to/from container
docker cp <id>:/app/logs ./logs
docker cp ./config.json <id>:/app/

# View image layer sizes
docker history myapp:latest

# Check disk usage
docker system df

# Remove stopped containers + dangling images + unused networks
docker system prune

# Also remove all unused images (not just dangling)
docker system prune -a

# Targeted cleanup
docker container prune   # Stopped containers
docker image prune -a    # Unused images
docker volume prune      # Unused volumes