Gitlab on port 8080

Most likely you have another service listening on 8080, I think the omnibus install have some service hooking 8080 - just use 8081 instead.

Edit: I just did a quick search and found that it's the unicorn server that is listening to 8080 with the original omnibus installer.

Note: You will only need to change the external_url in gitlab.rb, no other config file should have to be edited for this.

Edit#2: As @emeraldjava stated there is an option in the configuration file for using another unicorn port: #unicorn['port'] = '8080'

I solved this for Gitlab Omnibus (Community Edition, version 10.1.4) by first setting these in /etc/gitlab/gitlab.rb:

unicorn['port'] = 8081
gitlab_workhorse['auth_backend'] = "http://localhost:8081"

Then running:

sudo gitlab-ctl reconfigure
sudo gitlab-ctl restart

Additionally, if you are running GitLab behind an SSL reverse proxy, you may need to restart that service to get past the cached 502 error page.