Basics

Running Containers

docker run nginx              # run image
docker run -d nginx           # detached (background)
docker run -p 8080:80 nginx   # map port
docker run --name web nginx   # named container
docker run -it ubuntu bash    # interactive shell

Essential Commands

docker ps	List running containers
docker ps -a	List all containers (including stopped)
docker images	List local images
docker pull nginx	Download image from registry
docker info	System-wide information

Container Management

Lifecycle

docker start <id>	Start a stopped container
docker stop <id>	Graceful stop (SIGTERM)
docker kill <id>	Force stop (SIGKILL)
docker restart <id>	Restart container
docker rm <id>	Remove stopped container
docker rm -f <id>	Force remove (even if running)

Inspection & Debugging

docker logs <id>	View container logs
docker logs -f <id>	Follow logs (live)
docker exec -it <id> bash	Shell into running container
docker inspect <id>	Detailed container metadata (JSON)
docker top <id>	Running processes in container
docker stats	Live resource usage

Copying Files

docker cp file.txt :/app/    # host → container
docker cp :/app/log.txt ./   # container → host

Images

Building & Tagging

docker build -t myapp .          # build from Dockerfile
docker build -t myapp:v2 .       # with tag
docker tag myapp user/myapp:v2   # retag image

Publishing

docker login
docker push user/myapp:v2
docker pull user/myapp:v2

Image Management

docker images	List all local images
docker rmi <image>	Remove image
docker image prune	Remove dangling images
docker system prune	Remove all unused data
docker history <image>	Show image layer history

Dockerfile

Common Instructions

FROM node:20	Base image
WORKDIR /app	Set working directory
COPY . .	Copy files into image
RUN npm install	Run command during build
CMD ["node", "app.js"]	Default command at runtime
EXPOSE 3000	Document listening port
ENV NODE_ENV=production	Set environment variable
ARG VERSION=latest	Build-time variable
ENTRYPOINT ["python"]	Fixed executable (CMD = args)

Example Dockerfile

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --production
COPY . .
EXPOSE 3000
CMD ["node", "server.js"]

Volumes

Persistent Storage

docker volume create mydata
docker run -v mydata:/app/data nginx
docker run -v $(pwd):/app nginx  # bind mount

Volume Commands

docker volume ls	List volumes
docker volume inspect <v>	Volume details
docker volume rm <v>	Remove volume
docker volume prune	Remove unused volumes

Networks

Network Basics

docker network create mynet
docker run --network mynet --name api nginx
docker run --network mynet --name db postgres

Network Commands

docker network ls	List networks
docker network inspect <n>	Network details
docker network connect <n> <c>	Attach container to network
docker network rm <n>	Remove network

Containers on the same network can reach each other by name

Docker Compose

Example compose.yaml

services:
  web:
    build: .
    ports: ["3000:3000"]
    depends_on: [db]
  db:
    image: postgres:16
    environment:
      POSTGRES_PASSWORD: secret
    volumes: [pgdata:/var/lib/postgresql/data]
volumes:
  pgdata:

Compose Commands

docker compose up	Start all services
docker compose up -d	Start in background
docker compose down	Stop and remove containers
docker compose down -v	Also remove volumes
docker compose build	Rebuild images
docker compose logs -f	Follow all service logs
docker compose ps	List running services
docker compose exec web bash	Shell into a service

Useful Patterns

Cleanup Commands

docker system prune -a          # remove all unused
docker container prune           # remove stopped
docker image prune -a            # remove unused images

Quick Recipes

Temp container	`docker run --rm -it alpine sh`
Port check	`docker port`
Env vars	`docker run -e KEY=val image`
Env file	`docker run --env-file .env image`
Restart policy	`docker run --restart unless-stopped image`
Resource limit	`docker run --memory 512m --cpus 1 image`

DOCKER QUICK REFERENCE

DOCKER QUICK REFERENCE (continued)