Problem
On the domain controller the UMC does not show “Users” module to administer users:
Solution
Make sure your master domaincontroller is setup properly and force the role again with the following commands:
root@ucs:~# dpkg --configure -a
root@ucs:~# univention-install -f
root@ucs:~# univention-install univention-role-server-common univention-server-master --reinstall
root@ucs:~# univention-run-join-scripts