Docker Cheat Sheet

Introduction

Docker is a platform that enables developers to automate the deployment of applications inside lightweight, portable containers. Containers are isolated environments that include everything needed to run an application, ensuring consistency across different environments. This cheat sheet provides a detailed guide to essential Docker commands and concepts.

Docker Basics

1. Installation

Linux:

sudo apt-get update sudo apt-get install docker-ce docker-ce-cli containerd.io

Windows/Mac: Download and install Docker Desktop from the official website.

2. Hello World

Run a simple container:

docker run hello-world

3. Containers

List running containers:

docker ps -a

List all containers (including stopped ones):

Stop a running container:

docker stop <container_id>

Remove a container:

docker rm <container_id>

4. Images

List local images:

docker images

Remove an image:

docker rmi <image_id>

5. Dockerfile

Create a Dockerfile:

FROM ubuntu
RUN apt-get update && apt-get install -y python
CMD ["python", "--version"]

Build an image:

docker build -t my-python-app .

Run a container from the built image:

docker run my-python-app

Advanced Docker Commands

6. Networking

List networks:

docker network ls

Create a custom network:

docker network create my-network

7. Volumes

List volumes:

docker volume ls

Create a named volume:

docker volume create my-volume

8. Compose

Create a docker-compose.yml file:

version: '3'
services:
  web:
    image: nginx
    ports:
      - "80:80"

Run services defined in the docker-compose.yml file:

docker-compose up

9. Environment Variables

Set environment variables while running a container:

docker run -e MY_VARIABLE=value my-image

10. Docker Swarm

Initialize a Swarm:

docker swarm init

Deploy a stack:

docker stack deploy -c docker-compose.yml my-stack

Best Practices

11. Tags and Versioning

Use specific image tags for versioning:

docker pull nginx:1.18

12. Cleanup

Remove all stopped containers:

docker container prune

Remove all unused images:

docker image prune -a

13. Security

Avoid running containers as root:

docker run --user nonrootuser my-image

Limit container resources:

docker run --memory=512m --cpu-shares=2 my-image

Troubleshooting

14. Logs

View container logs:

docker logs <container_id>

15. Exec

Execute a command in a running container:

docker exec -it <container_id> /bin/bash

16. Inspect

Get detailed information about a container or image:

docker inspect <container_or_image_id>

Conclusion

Docker simplifies the process of packaging and deploying applications, providing a consistent environment across different systems. This cheat sheet covers essential Docker commands, concepts, and best practices to help you effectively manage containers in your development and deployment workflows. Explore Dockers documentation for more in-depth information and advanced use cases.