Installing Docker

Overview

Teaching: 10 min
Exercises: 15 min

Questions

• What equipment do I need?

• How do I install Docker?

• How do I test my installation?

• What are the main Docker concepts and commands I need to know?

Objectives

• Install Docker on your machine

• Understand the most basic concepts about images and containers

Installing Docker is relatively straightforward, particularly because of the excellent documentation they provide. Still you want to set aside some time to do it properly and test it out.

Installing

Go to the offical Docker site and their installation instructions to install Docker for your operating system.

Windows WSL2

In the episodes of this lesson that follow, we assume that Windows users have WSL2 activated with a Linux bash shell (e.g. Ubuntu) and Docker Desktop installed. All commands indicated with “bash” are expected to be typed in this Linux shell. Note that WSL2 can take around an hour to install.

If you are new to Linux bash shell, you should first follow the tutorial on shell environment. Make sure that you are familiar with the directory structure and that you know how to create and remove directories and how to create files and save them to a specific directory. Make also sure that you have an editor with which you are confortable. A common choice is VS Code, but you can use any other editor.

Testing

As you walk through their documentation, you will eventually come to a point where you will run a very simple test, usually involving their hello-world container.

You can find their documentation for this step here.

Testing their code can be summed up by the ability to run (without generating any errors) the following commands.

docker --version

docker run hello-world

Images and Containers

As it was mentioned above, there is ample documentation provided by Docker official sites. However, there are a couple of concepts that are crucial for the sake of using the container technology with CMS open data: container images and containers.

One can think of the container image as the main ingredients for preparing a dish, and the final dish as the container itself. You can prepare many dishes (containers) based on the same ingredients (container image). Images can exist without containers, whereas a container needs to run an image to exist. Therefore, containers are dependent on images and use them to construct a run-time environment and run an application.

The final dish, for us, is a container that can be thought of as an isolated machine (running on the host machine) with mostly its own operating system and the adequate software and run-time environment to process CMS open data.

Docker provides the ability to create, build and/or modify images, which can then be used to create containers. We will not use this aspect of the technology because, as you will see later, we will use an already-built and ready-to-use image in order to create our needed container.

Commands Cheatsheet

There are many Docker commands that can be executed for different tasks. However, the most useful for our purposes are the following. We will show some usage examples for some of these commands later. Feel free to explore other commands.

• Download image:

  docker pull <image>
  

• List images:

  docker image ls
  

• Remove images

  docker image rm <image>
  

  or

  docker rmi <image>
  

• List containers

  docker container ls -a
  

  or

  docker ps -a
  

  The -a option shows all containers (default shows just those running)

• Remove containers

  docker container rm <container>
  

  or

  docker rm <container>
  

• Create and start a container based on a specific image

  docker run [options] <image>
  

  This command will be used later to create our CMS open data container.

  The option -v for mounting a directory from the local computer to the container will also be used so that you can edit files on your normal editor and used them in the container:

  docker -v <directory-on-your-local-computer>:<directory-in-the-container> <image>
  

• Stop a running container

  docker stop <container>
  

• Attach a running (but detached) container

  docker attach <container>
  

• Start and attach a container that was stopped

  docker start -i <container>
  

• Copy files in or out of a container_run

  docker cp <container>:<path> <local path>
  docker cp <local path> <container>:<path>
  

Key Points

• For up-to-date details for installing Docker, the official documentation is the best bet.

• Make sure you were able to download and run Docker’s hello-world example.

• The concepts of image and container, plus the knowledge of certain Dockers commands, is all that is needed to start using CMS open data