We will see how to store the compose files of a Docker Swarm in git, together with encrypted authentication data to retrieve images from private repositories. We will access a private registry hosted by Gitlab. Authentication to the registry is done with a deploy token, which gives you a username and password giving access only to the relevant registry. Docker authentication Authentication to a docker registry is done with the command docker login -u $login --password $password (or alternatively with --password-stdin to avoid putting the password on the command line).