Enable relative URL in GitLab
Follow the steps below to enable relative URL in GitLab:
(Optional) If you run short on resources, you can temporarily free up some memory by shutting down Unicorn and Sidekiq with the following command:
sudo gitlab-ctl stop unicorn
sudo gitlab-ctl stop sidekiq
Set the external_url in /etc/gitlab/gitlab.rb:
external_url "https://example.com/gitlab"
In this example, the relative URL under which GitLab will be served will be /gitlab. Change it to your liking.
Reconfigure GitLab for the changes to take effect:
sudo gitlab-ctl reconfigure
Restart the services so that Unicorn and Sidekiq picks up the changes
sudo gitlab-ctl restart
Reference
https://docs.gitlab.com/ee/install/relative_url.html
https://docs.gitlab.com/omnibus/settings/configuration.html