Problem scenario
By default GitLab runs on port 8080. You want to run something else on the server with GitLab. How do you change the port that GitLab uses?
Solution
1. Edit the /etc/gitlab/gitlab.rb file.
Find the stanzas with for the "external_url".
Change it from this: http://x.x.x.x/
to this: http://x.x.x.x:555
(where x.x.x.x is either the external IP address or FQDN of the gitlab server and 555 is the desired non-standard port number that you want GitLab to listen on).
2. Then run this command: sudo gitlab-ctl reconfigure