The procedure is to switch the packages around over the top of the data.

You can’t restore a Community Edition backup into an EE install, or vice versa.

# sudo gitlab-backup restore BACKUP=1638647416_2021_12_04_14.5.1
Unpacking backup ... done
GitLab version mismatch:
  Your current GitLab version (14.5.1-ee) differs from the GitLab version in the backup!
  Please switch to the following version and try again:
  version: 14.5.1

If, like me, you thought you’d try restoring into a nice new EE install, and you encounter this error, you might then read the docs.

On RHEL and variants, at any rate, you can’t install CE directly over the top, you have to uninstall EE first.

# yum install gitlab-ce-14.5.1-ce.0.el7.x86_64.rpm
Loaded plugins: fastestmirror, langpacks
Examining gitlab-ce-14.5.1-ce.0.el7.x86_64.rpm: gitlab-ce-14.5.1-ce.0.el7.x86_64
Cannot install package gitlab-ce-14.5.1-ce.0.el7.x86_64. It is obsoleted by installed package gitlab-ee-14.5.1-ee.0.el7.x86_64
Error: Nothing to do

I guess it’d only be needed for the server running the install, where Rails is.  My other server – running Redis, PostgreSQL and Gitaly was left as EE.  The restore worked ok.

Turns out .. it’s the same the other way around as well.

# yum install gitlab-ee-14.5.1-ee.0.el7.x86_64.rpm
Loaded plugins: fastestmirror, langpacks
Examining gitlab-ee-14.5.1-ee.0.el7.x86_64.rpm: gitlab-ee-14.5.1-ee.0.el7.x86_64
Cannot install package gitlab-ee-14.5.1-ee.0.el7.x86_64. It is obsoleted by installed package gitlab-ce-14.5.1-ce.0.el7.x86_64