It was a while ago but the upgrade was from 9 to 11. The first problem was the error message didn't give me a simple command to go step wise through the upgrade like:
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Please upgrade to the next GitLab version before trying to upgrade to the latest. The command for upgrading to a previous version is as follows:
sudo apt-get install gitlab-ce=10.8.7-ce.0 -V
See the url below for available releases:
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Going from 10 to 11 was even more difficult because the gitlab.rb file format changed and I was missing required information that was not apparent from the error messages after running "gitlab-ctl reconfigure" (I think the error was Chef related but my memory is hazy, below are the GitLab issues that finally provided a hint). This wouldn't be so bad if my GitLab 10 instance was working but after going from 9 to 10, all I got was a blank page so at this point I had no choice but to go all the way.
After finally replacing the gitlab.rb file with the template and adding back info from the old file, I was able to finally run reconfigure and update as needed. Of course, I was soon alerted by coworkers that their commits were suddenly being blocked for failing a commit pipeline. Overall it was not a fun experience and I'd rather not upgrade GL unless I have to but I also don't want to skip versions if I have to repeat the hellish upgrade process by manually babying the upgrade.
Issues referenced:
https://gitlab.com/gitlab-org/omnibus-gitlab/issues/3610
https://gitlab.com/gitlab-org/gitlab-ce/issues/46219
https://gitlab.com/gitlab-org/omnibus-gitlab/issues/2153