Docker cheat sheet

What is Docker?

Docker is a tool used to deploy software across different platform without running into compatibility issues.

A Docker image is a lightweight, standalone, executable package of software that includes everything needed to run an application (code, libraries, settings, etc…). On a Linux system, Docker images are stored in /var/lib/docker.

A running instance of an image is called a container. A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another.

Cheat sheet

You can download a printable Linux command line cheat sheet here from Cheatography.

Another handy cheat sheet can be found here.

• Check Docker installation

docker version
docker run hello-world

• List docker images

docker images

• List dangling Docker images

docker images -f dangling=true

• Remove dangling images and build caches, all stopped containers and all networks not used by at least 1 container (useful to free some space).

docker system prune

• Remove docker image by ID

docker rmi -f IMAGE_ID

• Download a Docker image

docker pull IMAGE_NAME

• List running containers

docker ps
docker container ls

• List all containers

docker ps -a

• Stop a container

docker stop CONTAINER_ID

• Remove a container

docker rm CONTAINER_ID

• Stop all the containers

docker stop $(docker ps -a -q)

• Remove all the containers

docker rm $(docker ps -a -q)

• Run a docker image

docker run -it --rm IMAGE_ID

• Options of the run command:

-u $(id -u):$(id -g)       # assign a user and a group ID
--gpus all                 # allow GPU support
-it                        # run an interactive container inside a terminal
--rm                        # automatically remove the container after exiting
--name my_container        # give it a friendly name
-v ~/docker_ws:/notebooks  # share a directory between the host and the container
-p 8888:8888               # define port 8888 to connect to the container (for Jupyter notebooks)

• Open a new terminal in a running container

docker exec -it CONTAINER_ID bash

Create a new Docker image

There are 2 main methods.

Method 1 : Using a Dockerfile

1. Create a file called Dockerfile on your host machine.

    # getting base Ubuntu image
    FROM ubuntu
   
    # file author / maintainer
    LABEL maintainer="your_email_address"
   
    # update the repository sources list
    RUN apt-get update
   
    # print Hello World
    CMD ["echo", "Hello World"]
   

2. Build the image.

    docker build -t myimage:0.1 .
   

3. Run the image.

    docker run myimage:0.1
   

Method 2 : Commit a Docker image from a running container

Modify a running container and run this in another terminal.

docker commit CONTAINER_ID my_new_image