In normal operation, repmgrd monitors the state of the PostgreSQL node it is running on, and will take appropriate action if problems are detected, e.g. (if so configured) promote the node to primary, if the existing primary has been determined as failed.
However, repmgrd is unable to distinguish between planned outages (such as performing a switchover or installing PostgreSQL maintenance released), and an actual server outage. In versions prior to repmgr 4.2 it was necessary to stop repmgrd on all nodes (or at least on all nodes where repmgrd is configured for automatic failover) to prevent repmgrd from making unintentional changes to the replication cluster.
From repmgr 4.2, repmgrd can now be "paused", i.e. instructed not to take any action such as performing a failover. This can be done from any node in the cluster, removing the need to stop/restart each repmgrd individually.
Note: For major PostgreSQL upgrades, e.g. from PostgreSQL 10 to PostgreSQL 11, repmgrd should be shut down completely and only started up once the repmgr packages for the new PostgreSQL major version have been installed.