Introduction
# Docker Essentials
Essential Docker commands for container and image management.
## Container Lifecycle
### Running containers ```bash # Run container from image docker run nginx
# Run in background (detached) docker run -d nginx
# Run with name docker run --name my-nginx -d nginx
# Run with port mapping docker run -p 8080:80 -d nginx
# Run with environment variables docker run -e MY_VAR=value -d app
# Run with volume mount docker run -v /host/path:/container/path -d app
# Run with auto-remove on exit docker run --rm alpine echo "Hello"
# Interactive terminal docker run -it ubuntu bash ```
### Managing containers ```bash # List running containers docker ps
# List all containers (including stopped) docker ps -a
# Stop container docker stop container_name
# Start stopped container docker start container_name
# Restart container docker restart container_name
# Remove container docker rm container_name
# Force remove running container docker rm -f container_name
# Remove all stopped containers docker container prune ```
## Container Inspection & Debugging
### Viewing logs ```bash # Show logs docker logs container_name
# Follow logs (like tail -f) docker logs -f container_name
# Last 100 lines docker logs --tail 100 container_name
# Logs with timestamps docker logs -t container_name ```
### Executing commands ```bash # Execute command in running container docker exec container_name ls -la
# Interactive shell docker exec -it container_name bash
# Execute as specific user docker exec -u root -it container_name bash
# Execute with environment variable docker exec -e VAR=value container_name env ```
### Inspection ```bash # Inspect container details docker inspect container_name
# Get specific field (JSON path) docker inspect -f '{{.NetworkSettings.IPAddress}}' container_name
# View container stats docker stats
# View specific container stats docker stats container_name
# View processes in container docker top container_name ```
## Image Management
### Building images ```bash # Build from Dockerfile docker build -t myapp:1.0 .
# Build with custom Dockerfile docker build -f Dockerfile.dev -t myapp:dev .
# Build with build args docker build --build-arg VERSION=1.0 -t myapp .
# Build without cache docker build --no-cache -t myapp . ```
### Managing images ```bash # List images docker images
# Pull image from registry docker pull nginx:latest
# Tag image docker tag myapp:1.0 myapp:latest
# Push to registry docker push myrepo/myapp:1.0
# Remove image docker rmi image_name
# Remove unused images docker image prune
# Remove all unused images docker image prune -a ```
## Docker Compose
### Basic operations ```bash # Start services docker-compose up
# Start in background docker-compose up -d
# Stop services docker-compose down
# Stop and remove volumes docker-compose down -v
# View logs docker-compose logs
# Follow logs for specific service docker-compose logs -f web
# Scale service docker-compose up -d --scale web=3 ```
### Service management ```bash # List services docker-compose ps
# Execute command in service docker-compose exec web bash
# Restart service docker-compose restart web
# Rebuild service docker-compose build web
# Rebuild and restart docker-compose up -d --build ```
## Networking
```bash # List networks docker network ls
# Create network docker network create mynetwork
# Connect container to network docker network connect mynetwork container_name
# Disconnect from network docker network disconnect mynetwork container_name
# Inspect network docker network inspect mynetwork
# Remove network docker network rm mynetwork ```
## Volumes
```bash # List volumes docker volume ls
# Create volume docker volume create myvolume
# Inspect volume docker volume inspect myvolume
# Remove volume docker volume rm myvolume
# Remove unused volumes docker volume prune
# Run with volume docker run -v myvolume:/data -d app ```
## System Management
```bash # View disk usage docker system df
# Clean up everything unused docker system prune
# Clean up including unused images docker system prune -a
# Clean up including volumes docker system prune --volumes
# Show Docker info docker info
# Show Docker version docker version ```
## Common Workflows
**Development container:** ```bash docker run -it --rm \ -v $(pwd):/app \ -w /app \ -p 3000:3000 \ node:18 \ npm run dev ```
**Database container:** ```bash docker run -d \ --name postgres \ -e POSTGRES_PASSWORD=secret \ -e POSTGRES_DB=mydb \ -v postgres-data:/var/lib/postgresql/data \ -p 5432:5432 \ postgres:15 ```
**Quick debugging:** ```bash # Shell into running container docker exec -it container_name sh
# Copy file from container docker cp container_name:/path/to/file ./local/path
# Copy file to container docker cp ./local/file container_name:/path/in/container ```
**Multi-stage build:** ```dockerfile # Dockerfile FROM node:18 AS builder WORKDIR /app COPY package*.json ./ RUN npm install COPY . . RUN npm run build
FROM nginx:alpine COPY --from=builder /app/dist /usr/share/nginx/html ```
## Useful Flags
**`docker run` flags:** - `-d`: Detached mode (background) - `-it`: Interactive terminal - `-p`: Port mapping (host:container) - `-v`: Volume mount - `-e`: Environment variable - `--name`: Container name - `--rm`: Auto-remove on exit - `--network`: Connect to network
**`docker exec` flags:** - `-it`: Interactive terminal - `-u`: User - `-w`: Working directory
## Tips
- Use `.dockerignore` to exclude files from build context - Combine `RUN` commands in Dockerfile to reduce layers - Use multi-stage builds to reduce image size - Always tag your images with versions - Use `--rm` for one-off containers - Use `docker-compose` for multi-container apps - Clean up regularly with `docker system prune`
## Documentation
Official docs: https://docs.docker.com/ Dockerfile reference: https://docs.docker.com/engine/reference/builder/ Compose file reference: https://docs.docker.com/compose/compose-file/