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9.7. Configuring Startup Order for Resource Dependencies not Managed by Pacemaker (Red Hat Enterprise Linux 7.4 and later)

It is possible for a cluster to include resources with dependencies that are not themselves managed by the cluster. In this case, you must ensure that those dependencies are started before Pacemaker is started and stopped after Pacemaker is stopped.
As of Red Hat Enterprise Linux 7.4, you can configure your startup order to account for this situation by means of the systemd resource-agents-deps target. You can create a systemd drop-in unit for this target and Pacemaker will order itself appropriately relative to this target.
For example, if a cluster includes a resource that depends on the external service foo that is not managed by the cluster, you can create the drop-in unit /etc/systemd/system/resource-agents-deps.target.d/foo.conf that contains the following:
[Unit]
Requires=foo.service
After=foo.service
After creating a drop-in unit, run the systemctl daemon-reload command.
A cluster dependency specified in this way can be something other than a service. For example, you may have a dependency on mounting a file system at /srv, in which case you would create a systemd file srv.mount for it according to the systemd documentation, then create a drop-in unit as described here with srv.mount in the .conf file instead of foo.service to make sure that Pacemaker starts after the disk is mounted.