When installing from source, make sure you have reviewed the latest installation guides for your platform for the GitLab branch you want (for example, 12-0). The instructions in this book will ultimately be out of date. Furthermore, if you run into an issue, you can try to find an answer on the GitLab forum: https://forum.gitlab.com/c/troubleshooting. If the problem turns out to be a bug or unwanted behavior by GitLab, you can open an issue at https://gitlab.com/gitlab-org/gitlab-ce/issues. The following sections will feature the exact installation instructions for a Debian version.