Docker

Containerization platform for developing, shipping, and running applications.

Basic Commands

COMMAND	DESCRIPTION
docker run <image>	Run a container from an image
docker ps	List running containers
docker ps -a	List all containers (including stopped)
docker stop <container>	Stop a running container
docker start <container>	Start a stopped container
docker restart <container>	Restart a container
docker rm <container>	Remove a container
docker rmi <image>	Remove an image

Images

COMMAND	DESCRIPTION
docker pull <image>	Pull an image from a registry
docker images	List locally available images
docker build -t <name> .	Build an image from Dockerfile
docker tag <image> <new-tag>	Tag an image
docker push <image>	Push an image to registry
docker inspect <image>	Show image details
docker history <image>	Show image history

Container Management

COMMAND	DESCRIPTION
docker exec -it <container> /bin/bash	Execute command in container
docker logs <container>	Show container logs
docker logs -f <container>	Follow log output
docker port <container>	Show port mappings
docker stats	Show live container stats
docker cp <src> <dest>	Copy files between host/container
docker diff <container>	Show container filesystem changes

Network & Volumes

COMMAND	DESCRIPTION
docker network ls	List networks
docker network create <name>	Create a network
docker network connect <net> <container>	Connect container to network
docker volume ls	List volumes
docker volume create <name>	Create a volume
docker volume rm <volume>	Remove a volume

Docker Compose

COMMAND	DESCRIPTION
docker compose up	Create and start services
docker compose up -d	Start services in background
docker compose down	Stop and remove services
docker compose ps	List services
docker compose logs	View service logs
docker compose exec <service> <cmd>	Execute command in service
docker compose build	Rebuild services
docker compose pull	Pull service images

Cleanup

COMMAND	DESCRIPTION
docker system prune	Remove unused data
docker system prune -a	Remove all unused data
docker container prune	Remove stopped containers
docker image prune -a	Remove unused images
docker volume prune	Remove unused volumes

Advanced Usage

Run with Options

# Run in background with port mapping
docker run -d -p 8080:80 --name myapp nginx

# Mount volume
docker run -v /host/path:/container/path nginx

# Set environment variables
docker run -e KEY=value nginx

# Auto-restart on failure
docker run --restart=on-failure:5 nginx

Resource Limits

# Limit memory
docker run -m 512m nginx

# Limit CPU (0.5 = 50% of 1 core)
docker run --cpus=0.5 nginx

# Set memory reservation
docker run --memory-reservation=256m nginx

Debugging

# View container details
docker inspect <container>

# Check container process
docker top <container>

# View live resource usage
docker stats

# Export container filesystem
docker export <container> > backup.tar

Security

COMMAND	DESCRIPTION
docker scan <image>	Scan image for vulnerabilities
docker run --read-only	Run with read-only filesystem
docker run --user nobody	Run as non-root user
docker run --cap-drop=ALL	Drop all Linux capabilities

Best Practices

• Use specific image versions, not latest
• Use .dockerignore to exclude unnecessary files
• Combine RUN commands to reduce layers
• Use multi-stage builds for smaller images
• Scan images for security vulnerabilities
• Don't run containers as root user
• Set resource limits for production containers

TIP

Use docker compose for multi-container applications and Docker Swarm for orchestration at scale.