Building Docker images

In this section, we will see how to build Docker images using two different methods: the docker commit command and a Dockerfile automated build.

docker commit

Let's start with an example and prepare an image with the Git and JDK toolkits. We will use Ubuntu 20.04 as a base image. There is no need to create it; most base images are available in the Docker Hub registry. Proceed as follows:

1. Run a container from ubuntu:20.04 and connect it to its command line, like this:

   $ docker run -i -t ubuntu:20.04 /bin/bash

We've pulled the ubuntu:20.04 image, run it as a container, and then called the /bin/bash command in an interactive way (-i flag). You should see the Terminal of the container. Since containers are stateful and writable, we can do anything we want in its Terminal.

2. Install the Git toolkit, as follows:

   root@dee2cb192c6c:/# apt-get update
   root@dee2cb192c6c...