Docker Cheat Sheet: Every Command You Actually Need

Quick Answer: docker run -d --name myapp -p 8080:80 nginx starts an nginx container in the background on port 8080. docker ps lists running containers. docker logs myapp shows logs. docker exec -it myapp bash opens a shell inside the container. docker stop myapp stops it.

Container Lifecycle

Run a Container

# Basic run (foreground)
docker run nginx

# Detached (background) with name and port mapping
docker run -d --name web -p 8080:80 nginx

# Run and auto-remove when stopped
docker run --rm -it ubuntu bash

# Run with environment variables
docker run -d --name db -e MYSQL_ROOT_PASSWORD=secret -p 3306:3306 mysql:8

# Run with volume mount
docker run -d --name web -v /host/path:/container/path nginx

# Run with resource limits
docker run -d --name app --memory=512m --cpus=1.5 myapp

Manage Containers

# List running containers
docker ps

# List ALL containers (including stopped)
docker ps -a

# Stop a container
docker stop web

# Start a stopped container
docker start web

# Restart
docker restart web

# Kill (force stop)
docker kill web

# Remove a stopped container
docker rm web

# Remove a running container (force)
docker rm -f web

# Stop and remove ALL containers
docker stop $(docker ps -q) && docker rm $(docker ps -aq)

Inspect and Debug

# View logs
docker logs web
docker logs -f web              # Follow (tail)
docker logs --tail 100 web      # Last 100 lines
docker logs --since 1h web      # Last hour

# Execute command inside running container
docker exec -it web bash        # Interactive shell
docker exec web cat /etc/hosts  # Run single command

# Container details
docker inspect web
docker inspect --format='{{.NetworkSettings.IPAddress}}' web

# Resource usage (live)
docker stats
docker stats web

# See running processes inside container
docker top web

# Copy files to/from container
docker cp localfile.txt web:/path/in/container/
docker cp web:/path/in/container/file.txt ./local/

Images

# List images
docker images

# Pull an image
docker pull nginx:latest
docker pull nginx:1.25-alpine   # Specific version

# Build from Dockerfile
docker build -t myapp .
docker build -t myapp:v2 -f Dockerfile.prod .

# Tag an image
docker tag myapp myregistry.com/myapp:v2

# Push to registry
docker push myregistry.com/myapp:v2

# Remove an image
docker rmi nginx

# Remove all unused images
docker image prune -a

# Image history (see layers)
docker history myapp

# Save/load images (for transfer without registry)
docker save myapp > myapp.tar
docker load < myapp.tar

Volumes

# Create a named volume
docker volume create mydata

# List volumes
docker volume ls

# Inspect a volume
docker volume inspect mydata

# Use a volume in a container
docker run -d -v mydata:/var/lib/mysql mysql:8

# Bind mount (host directory)
docker run -d -v $(pwd)/data:/app/data myapp

# Remove a volume
docker volume rm mydata

# Remove ALL unused volumes
docker volume prune

Networks

# List networks
docker network ls

# Create a network
docker network create mynet

# Run container on a network
docker run -d --name web --network mynet nginx

# Connect running container to network
docker network connect mynet web

# Disconnect
docker network disconnect mynet web

# Inspect network (see connected containers)
docker network inspect mynet

# Containers on the same network can reach each other by name:
# From 'web' container: curl http://api:3000 (if 'api' is on same network)

Docker Compose

Basic compose.yml

services:
  web:
    image: nginx:alpine
    ports:
      - "8080:80"
    volumes:
      - ./html:/usr/share/nginx/html
    depends_on:
      - api

  api:
    build: ./api
    environment:
      - DATABASE_URL=postgres://db:5432/myapp
    depends_on:
      - db

  db:
    image: postgres:16-alpine
    environment:
      - POSTGRES_PASSWORD=secret
    volumes:
      - pgdata:/var/lib/postgresql/data

volumes:
  pgdata:

Compose Commands

# Start all services (detached)
docker compose up -d

# Stop all services
docker compose down

# Stop and remove volumes too
docker compose down -v

# Rebuild and start
docker compose up -d --build

# View logs
docker compose logs -f
docker compose logs api         # Single service

# Scale a service
docker compose up -d --scale api=3

# Execute command in a service
docker compose exec api bash

# List services
docker compose ps

Dockerfile Reference

# Start from a base image
FROM node:20-alpine

# Set working directory
WORKDIR /app

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

# Install dependencies
RUN npm ci --omit=dev

# Copy app source
COPY . .

# Expose port (documentation)
EXPOSE 3000

# Set environment variable
ENV NODE_ENV=production

# Health check
HEALTHCHECK --interval=30s --timeout=3s \
  CMD curl -f http://localhost:3000/health || exit 1

# Run the app
CMD ["node", "server.js"]

Multi-stage Build (smaller images)

# Build stage
FROM node:20 AS builder
WORKDIR /app
COPY . .
RUN npm ci && npm run build

# Production stage
FROM node:20-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
CMD ["node", "dist/server.js"]

Cleanup

# Remove all stopped containers
docker container prune

# Remove all unused images
docker image prune -a

# Remove all unused volumes
docker volume prune

# Remove all unused networks
docker network prune

# Nuclear option: remove EVERYTHING unused
docker system prune -a --volumes

# Check disk usage
docker system df

Common Patterns

Run a one-off command

# Run a script and remove container after
docker run --rm -v $(pwd):/work -w /work python:3.12 python script.py

Quick database for development

# PostgreSQL
docker run -d --name pg -e POSTGRES_PASSWORD=dev -p 5432:5432 postgres:16-alpine

# MySQL
docker run -d --name mysql -e MYSQL_ROOT_PASSWORD=dev -p 3306:3306 mysql:8

# Redis
docker run -d --name redis -p 6379:6379 redis:alpine

# MongoDB
docker run -d --name mongo -p 27017:27017 mongo:7

Troubleshooting

# Container won't start? Check logs:
docker logs mycontainer

# Container exits immediately? Run interactively:
docker run -it myimage bash

# Can't connect to container port?
docker port mycontainer          # Check port mapping
docker inspect mycontainer | grep IPAddress

# Out of disk space?
docker system df                 # Check usage
docker system prune -a           # Clean up

See Also

• systemd Guide
• Server Hardening Guide
• Nginx vs Apache
• Cron Job Examples