Getting Started With Docker

Prerequisites

  1. Install Docker on your laptop:

To check if the installation was successful, open up your favorite Terminal (Mac,Linux) or the Docker Terminal (Windows) and try running

$ docker version
Client: Docker Engine - Community
 Version:           20.10.12
 API version:       1.41
 Go version:        go1.16.12
 Git commit:        e91ed57
 Built:             Mon Dec 13 11:45:41 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.12
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.16.12
  Git commit:       459d0df
  Built:            Mon Dec 13 11:44:05 2021
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.4.12
  GitCommit:        7b11cfaabd73bb80907dd23182b9347b4245eb5d
 runc:
  Version:          1.0.2
  GitCommit:        v1.0.2-0-g52b36a2
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

Note

If you do not have Docker installed on your laptop, you could also use https://labs.play-with-docker.com/

  1. Create a Docker Hub account

Having a Docker Hub account makes it easier to share your containers with other researchers. Use the Docker CLI to login to Docker Hub to be able to push images to your repository:

$ docker login
(Enter username/password)
  1. Create a TACC Account

We will use the TACC account later in this workshop to log in to Frontera and run our containers on an HPC system with Singularity (Apptainer).

EXERCISE

While everyone gets set up, take a few minutes to run docker --help and a few examples of docker <verb> --help to make sure you can find and read the help text.

Working with Images from Docker Hub

To introduce ourselves to some of the most essential Docker commands, we will go through the process of listing images that are currently available on our local machines, and we will pull a ‘hello-world’ image from Docker Hub. Then we will run the ‘hello-world’ image to see what happens.

List images on your local machine with the docker images command. This peaks into the Docker daemon, which is shared by all users on this system, to see which images are available, when they were created, and how large they are:

$ docker images
REPOSITORY           TAG                 IMAGE ID       CREATED        SIZE
ubuntu               18.04               6ad7e71ba7d    2 days ago     63.2MB

Note

If this is your first time using Docker, you may not have any images stored on your local machine.

Pull an image from Docker hub with the docker pull command. This looks through the Docker Hub registry and downloads the ‘latest’ version of that image:

$ docker pull hello-world
Using default tag: latest
latest: Pulling from library/hello-world
2db29710123e: Pull complete
Digest: sha256:10d7d58d5ebd2a652f4d93fdd86da8f265f5318c6a73cc5b6a9798ff6d2b2e67
Status: Downloaded newer image for hello-world:latest
docker.io/library/hello-world:latest

Run the image we just pulled with the docker run command. In this case, running the container will execute a simple shell script inside the container that has been configured as the ‘default command’ when the image was built:

$ docker run hello-world

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

Verify that the image you just pulled is now available on your local machine:

$ docker images
REPOSITORY           TAG                 IMAGE ID       CREATED        SIZE
ubuntu               18.04               6ad7e71ba7d    2 days ago     63.2MB
hello-world          latest              feb5d9fea6a5   7 months ago   13.3kB

Check to see if any containers are still running using docker ps:

$ docker ps
CONTAINER ID   IMAGE     COMMAND   CREATED   STATUS    PORTS     NAMES

EXERCISE

The command docker ps shows only currently running containers. Pull up the help text for that command and figure out how to show all containers, not just currently running containers.

EXERCISE

Closely inspect metadata for your downloaded image(s) using the docker inspect command:

$ docker inspect hello-world
[
    {
        "Id": "sha256:feb5d9fea6a5e9606aa995e879d862b825965ba48de054caab5ef356dc6b3412",
        "RepoTags": [
            "hello-world:latest"
...

Docker Core Commands

Command Usage
docker login Authenticate to Docker Hub using username and password
docker images List images on the local machine
docker ps List containers on the local machine
docker pull Download an image from Docker Hub
docker run Run an instance of an image (a container)
docker inspect Provide detailed information on Docker objects
docker rmi Delete an image
docker rm Delete a container
docker stop Stop a container
docker build Build a docker image from a Dockerfile in the current working directory
docker tag Add a new tag to an image
docker push Upload an image to Docker Hub

Additional Resources

The command line tools are very well documented:

$ docker --help
shows all docker options and summaries

$ docker COMMAND --help
shows options and summaries for a particular command