To create a witness server, set up a normal PostgreSQL instance on a server in the same physical location as the cluster's primary server.
This instance should *not* be on the same physical host as the primary server, as otherwise if the primary server fails due to hardware issues, the witness server will be lost too.
Note: repmgr 3.3 and earlier provided a repmgr create witness command, which would automatically create a PostgreSQL instance. However this often resulted in an unsatisfactory, hard-to-customise instance.
The witness server should be configured in the same way as a normal repmgr node; see section Configuration.
Register the witness server with repmgr witness register. This will create the repmgr extension on the witness server, and make a copy of the repmgr metadata.
Note: As the witness server is not part of the replication cluster, further changes to the repmgr metadata will be synchronised by repmgrd.
Once the witness server has been configured, repmgrd should be started; for more details see Using a witness server with repmgrd.
To unregister a witness server, use repmgr witness unregister.