The univention-system-check reports errors about univention-s4-connector:
Critical:Check join status
“univention-check-join-status” returned a problem with the domain join.
Warning: ‘univention-s4-connector’ is not configured.
Error: Not all install files configured: 1 missing
See Manual: Analysis of listener/notifier problems or run the join-scripts via “Domain join” module.
The S4-connector synchronizes data between the OpenLDAP and Samba services. In order to prevent double syncing the s4-connector is only allowed to run as a single instance in the UCS domain. This is usually the master server but can be any server where Samba is running.
The univention-system-check does not prove the existence of the s4-connector in the domain and complains about the not configured s4-connector.
This error can be ignored as the s4-connector runs fine on an other server.
The error is reliable if it appears on a host where s4-connector is usually running.
(kudos to @Moritz_Bunkus)
The system check scripts are tools developed for use by Univention support team for quickly gathering an overview of the state of a system. As such it works more or less independent of the UCS version it is run on — unlike the UMC module “system diagnosis” which is highly version dependent. Both tools contain a different set of checks.