GitLab has native support for private docker registries: https://docs.gitlab.com/ce/user/project/container_registry.html
In order to test the availability of the private docker registry hosted by GitLab, type the following command in a shell and enter your GitLab credentials:
docker login gitlab.playground.test:4567
This login will be used directly in the pipelines that build and push images to the private docker registry. Each project can build it's own image and push it to a private docker registry.
This private docker registry can have several uses, first of all can be used as the docker images source for deploying and distributing our applications. Another possible use of the private docker registry will be shown in the next section.