The first stage in our continuous deployment pipeline will contain quite a few steps. We'll need to check out the code, to run unit tests and any other static analysis, to build a Docker image, and to push it to the registry. If we define CI as a set of automated steps followed with manual operations and validations, we can say that the steps we are about to execute can be qualified as CI.
The only thing we truly need to make all those steps work is Docker client with the access to Docker server. One of the containers of the cd Pod already contains it. If you take another look at the definition, you'll see that we are mounting Docker socket so that the Docker client inside the container can issue commands to Docker server running on the host. Otherwise, we would be running Docker-in-Docker, and that is not a very good...