Docker Command Cheatsheet | Quick Reference

📦 Docker Basics

💡 What is Docker?

Docker packages applications and their dependencies into containers - lightweight, portable units that run consistently across different environments. Think of containers as self-contained boxes that have everything an application needs to run.

Key Concepts

🧩 Core Components

Image: A blueprint/template for containers (like a recipe)
Container: A running instance of an image (like a meal made from the recipe)
Volume: Persistent storage that survives container restarts
Network: How containers communicate with each other and the outside world
Docker Compose: Tool for defining multi-container applications

Basic Commands

Check Docker Version

Verify Docker is installed and see version info

docker --version
docker version
docker info

Test Docker Installation

Run a test container to verify everything works

docker run hello-world

Pull an Image

Download an image from Docker Hub

docker pull ubuntu:22.04
docker pull nginx:latest

Run a Container

Create and start a container from an image

# Basic run
docker run nginx

# Run with custom name
docker run --name my-nginx nginx

# Run in background (detached mode)
docker run -d nginx

# Run with port mapping
docker run -d -p 8080:80 nginx

# Run with environment variables
docker run -d -e "MY_VAR=value" nginx

🎼 Docker Compose

💡 What is Docker Compose?

Docker Compose lets you define and run multi-container applications using a YAML file. Instead of managing each container separately, you describe your entire application stack in docker-compose.yaml and control everything with simple commands.

Essential Compose Commands

Start Services (Detached)

Start all services defined in docker-compose.yaml in the background

docker compose up -d

Start Services (Foreground)

Start services and see logs in real-time (Ctrl+C to stop)

docker compose up

Stop Services

Stop running containers but keep them for restart

docker compose stop

Start Stopped Services

Restart previously stopped services

docker compose start

Restart Services

Stop and start services in one command

docker compose restart

# Restart specific service
docker compose restart backend

Stop and Remove Containers

Stop services and remove containers (volumes remain intact)

docker compose down

Stop and Remove Everything (INCLUDING DATA!)

⚠️ Nuclear option - removes containers AND volumes (all data lost)

docker compose down -v

🚨 Critical Warning

docker compose down -v deletes ALL data stored in volumes. Only use this when you want a complete reset or are removing an application permanently.

View Service Status

See which containers are running

docker compose ps

View Logs

See output from all services

# All logs
docker compose logs

# Follow logs (real-time)
docker compose logs -f

# Last 100 lines
docker compose logs --tail=100

# Specific service
docker compose logs backend

# Follow specific service
docker compose logs -f backend

Pull Latest Images

Download updated versions of images

docker compose pull

Build Images

Build custom images defined in docker-compose.yaml

# Build all images
docker compose build

# Build without cache
docker compose build --no-cache

# Build specific service
docker compose build backend

Execute Command in Service

Run a command inside a running container

# Get shell access
docker compose exec backend bash

# Run single command
docker compose exec backend ls -la

# Run as different user
docker compose exec -u postgres postgres psql

Compose File Validation

Validate Configuration

Check if docker-compose.yaml is valid

docker compose config

🔄 Container Lifecycle Management

Starting & Stopping

Start Container

docker start <container_name_or_id>

Stop Container

Gracefully stop (sends SIGTERM, waits, then SIGKILL)

docker stop <container_name_or_id>

# Stop with timeout (seconds)
docker stop -t 30 <container_name_or_id>

Restart Container

docker restart <container_name_or_id>

Kill Container

Force stop immediately (sends SIGKILL)

docker kill <container_name_or_id>

Remove Container

Delete stopped container

# Remove stopped container
docker rm <container_name_or_id>

# Force remove running container
docker rm -f <container_name_or_id>

# Remove with volumes
docker rm -v <container_name_or_id>

Listing & Inspection

List Running Containers

docker ps

List All Containers

Including stopped containers

docker ps -a

Inspect Container

Get detailed information about a container

docker inspect <container_name_or_id>

# Get specific field
docker inspect --format='{{.State.Status}}' <container>

View Container Logs

# All logs
docker logs <container_name_or_id>

# Follow logs (real-time)
docker logs -f <container_name_or_id>

# Last 100 lines
docker logs --tail 100 <container_name_or_id>

# With timestamps
docker logs -t <container_name_or_id>

Execute Command in Running Container

# Interactive shell
docker exec -it <container_name> bash

# Or sh if bash not available
docker exec -it <container_name> sh

# Run single command
docker exec <container_name> ls -la /app

# As different user
docker exec -u postgres <container_name> psql

Copy Files To/From Container

# Copy from container to host
docker cp <container>:/path/to/file /local/path

# Copy from host to container
docker cp /local/file <container>:/path/to/destination

📊 Monitoring & Performance

View Resource Usage

Real-time stats for all running containers

docker stats

# Specific container
docker stats <container_name>

# No streaming (one-time)
docker stats --no-stream

View Running Processes

See processes inside container

docker top <container_name>

View Port Mappings

docker port <container_name>

System-Wide Information

# Disk usage
docker system df

# Detailed disk usage
docker system df -v

# System information
docker info

Monitor Events

Real-time events from Docker daemon

docker events

# Filter by type
docker events --filter 'type=container'

# Filter by event
docker events --filter 'event=start'

💾 Volumes & Data Management

💡 What are Volumes?

Volumes are Docker's way of persisting data beyond container lifecycles. When you delete a container, volumes remain intact unless explicitly removed. This is how your data survives updates and restarts.

List Volumes

docker volume ls

Create Volume

docker volume create my_volume

Inspect Volume

See volume details including mount point

docker volume inspect my_volume

Remove Volume

⚠️ This deletes data permanently

docker volume rm my_volume

# Force remove
docker volume rm -f my_volume

Backup Volume

Create a tarball backup of volume data

docker run --rm \
  -v my_volume:/data \
  -v $(pwd):/backup \
  ubuntu tar czf /backup/backup.tar.gz /data

Restore Volume

Restore from backup tarball

docker run --rm \
  -v my_volume:/data \
  -v $(pwd):/backup \
  ubuntu tar xzf /backup/backup.tar.gz -C /

Volume Usage in Containers

Mount Volume to Container

# Named volume
docker run -d -v my_volume:/app/data nginx

# Bind mount (host directory)
docker run -d -v /host/path:/container/path nginx

# Read-only mount
docker run -d -v my_volume:/app/data:ro nginx

🌐 Networks

💡 Docker Networks

Networks allow containers to communicate with each other and the outside world. Docker creates isolated networks where containers can find each other by name.

List Networks

docker network ls

Create Network

# Bridge network (default type)
docker network create my_network

# Custom subnet
docker network create --subnet=172.20.0.0/16 my_network

Inspect Network

docker network inspect my_network

Connect Container to Network

docker network connect my_network <container_name>

Disconnect Container from Network

docker network disconnect my_network <container_name>

Remove Network

docker network rm my_network

📦 Image Management

List Images

docker images

# With digests
docker images --digests

# Show all (including intermediate)
docker images -a

Pull Image

# Latest version
docker pull nginx

# Specific version
docker pull nginx:1.25

# From different registry
docker pull ghcr.io/user/image:tag

Search Images

Search Docker Hub

docker search nginx

# Limit results
docker search --limit 10 nginx

Remove Image

docker rmi <image_name_or_id>

# Force remove
docker rmi -f <image_name_or_id>

# Remove multiple
docker rmi image1 image2 image3

Tag Image

Create alias for image

docker tag source_image:tag target_image:tag

# Example
docker tag nginx:latest myregistry.com/nginx:v1

Build Image from Dockerfile

# Build from current directory
docker build -t my-image:tag .

# Build without cache
docker build --no-cache -t my-image:tag .

# Build with build args
docker build --build-arg VERSION=1.0 -t my-image:tag .

Save & Load Images

Export/import images as tar files

# Save image to file
docker save -o my-image.tar my-image:tag

# Load image from file
docker load -i my-image.tar

View Image History

See image layers and how it was built

docker history <image_name>

🧹 Cleanup & Maintenance

⚠️ Before Cleanup

Always check what will be removed with docker system df first. Pruning operations are permanent!

Remove Stopped Containers

docker container prune

# Without confirmation prompt
docker container prune -f

Remove Unused Images

Removes dangling images (not tagged and not used)

docker image prune

# Remove ALL unused images
docker image prune -a

Remove Unused Volumes

⚠️ This deletes data in unused volumes!

docker volume prune

# Without confirmation
docker volume prune -f

Remove Unused Networks

docker network prune

Complete System Cleanup

Remove all unused containers, networks, images (both dangling and unreferenced)

# Safe cleanup (keeps volumes)
docker system prune

# Aggressive cleanup (includes volumes)
docker system prune -a --volumes

# Without confirmation
docker system prune -af

🚨 Nuclear Option

Complete Docker Reset:

# Stop all containers
docker stop $(docker ps -aq)

# Remove all containers
docker rm $(docker ps -aq)

# Remove all images
docker rmi $(docker images -q)

# Remove all volumes
docker volume rm $(docker volume ls -q)

# Remove all networks
docker network rm $(docker network ls -q)

This removes EVERYTHING. Only use if you want a complete fresh start!

🔧 Troubleshooting

Common Issues

⚠️ Port Already in Use

Error: Error starting userland proxy: listen tcp 0.0.0.0:9001: bind: address already in use

Solution:

# Find what's using the port
sudo lsof -i :9001
sudo netstat -tulpn | grep :9001

# Kill the process or change port in docker-compose.yaml

⚠️ Container Keeps Restarting

Check logs for errors:

docker logs --tail 100 <container_name>

⚠️ Out of Disk Space

# Check Docker disk usage
docker system df

# Clean up
docker system prune -a
docker volume prune

⚠️ Permission Denied

Error: Got permission denied while trying to connect to the Docker daemon socket

Solution:

# Add user to docker group
sudo usermod -aG docker $USER

# Log out and back in for changes to take effect
# Or start new shell
newgrp docker

⚠️ Network Issues

Container can't reach internet or other containers

# Restart Docker daemon
sudo systemctl restart docker

# Or recreate network
docker network rm <network_name>
docker network create <network_name>

🎯 Common Patterns

Complete Application Reset

Reset Application (Delete All Data)

cd ~/project
docker compose down -v  # Remove containers + volumes
docker compose pull     # Get latest images
docker compose up -d    # Start fresh

Update Application

Update to Latest Version (Keep Data)

cd ~/project
docker compose pull     # Download latest
docker compose up -d    # Recreate containers with new images

Backup and Restore

Backup Before Changes

# Stop services
docker compose stop

# Backup volumes
docker run --rm -v project_data:/data -v $(pwd):/backup \
  ubuntu tar czf /backup/backup-$(date +%Y%m%d).tar.gz /data

# Restart
docker compose start

Development vs Production

Multiple Compose Files

# Development
docker compose -f docker-compose.yaml -f docker-compose.dev.yaml up

# Production
docker compose -f docker-compose.yaml -f docker-compose.prod.yaml up -d

Debugging Running Container

Interactive Shell Access

# Get shell in running container
docker exec -it <container_name> bash

# Or sh if bash isn't available
docker exec -it <container_name> sh

# Run single command
docker exec <container_name> ls -la /app

✅ Best Practices

Project Organization

📂 Directory Structure

~/projects/
  ├── penpot/
  │   ├── docker-compose.yaml
  │   ├── .env
  │   └── README.md
  ├── nextcloud/
  │   ├── docker-compose.yaml
  │   └── data/
  └── ...

Docker Compose Best Practices

Always use named volumes instead of anonymous volumes
Use .env files for sensitive data (passwords, API keys)
Pin image versions - use postgres:15 not postgres:latest
Add restart policies - restart: unless-stopped
Use depends_on to manage service startup order
Document your setup in README.md
Use health checks to ensure services are actually running
Limit container resources (memory, CPU) in production

Maintenance Routine

Weekly Cleanup

# Remove unused images, containers, networks
docker system prune

# Remove unused volumes (be careful!)
docker volume prune

Check Updates

# Check for new images
docker compose pull

# View what would change
docker compose up --no-start

# Apply updates
docker compose up -d

Security Tips

🔒 Security Checklist

Never store passwords in docker-compose.yaml - use .env files
Add .env to .gitignore
Use official images from trusted sources
Keep images updated regularly
Don't run containers as root unless necessary
Limit container resources (memory, CPU) in production
Use read-only file systems where possible
Scan images for vulnerabilities with docker scan

When Things Go Wrong

🚨 Emergency Recovery

If everything is broken:

# 1. Stop everything
docker compose down

# 2. Check logs for errors
docker compose logs --tail=100

# 3. Try starting with verbose output
docker compose up

# 4. If still broken, nuclear option:
docker compose down -v
docker system prune -a
docker compose up -d

⚡ Quick Reference Card

Task	Command
Start services	`docker compose up -d`
Stop services	`docker compose stop`
Restart services	`docker compose restart`
View logs	`docker compose logs -f`
Update images	`docker compose pull && docker compose up -d`
Remove containers (keep data)	`docker compose down`
Complete reset	`docker compose down -v`
Check status	`docker compose ps`
Clean unused resources	`docker system prune`
Shell into container	`docker exec -it <name> bash`
View resource usage	`docker stats`
Copy files to container	`docker cp file <name>:/path`
List all containers	`docker ps -a`
List all images	`docker images`
List volumes	`docker volume ls`