If you are using the Omnibus package on Ubuntu, don't upgrade! It just broke my instance. and can't find out what's wrong. Great features... It was a big mistake to trust GitLab, I already predicted they will have problems.
No, I'm not joking. I've had the omnibus package break my Gitlab as well and the bugs survived even full reconfigures and restarts. Rebooting the server fixed it even though it makes no sense.