Upon startup, it will identify the logical volume by loading the JSON file in /etc/ceph/osd/{id}-{uuid}.json corresponding to the instance name of the systemd unit.

After identifying the correct volume it will then proceed to mount it by using the OSD destination conventions, that is:

/var/lib/ceph/osd/{cluster name}-{osd id}

For our example OSD with an id of 0, that means the identified device will be mounted at:


Once that process is complete, a call will be made to start the OSD:

systemctl start ceph-osd@0

The systemd portion of this process is handled by the ceph-volume simple trigger sub-command, which is only in charge of parsing metadata coming from systemd and startup, and then dispatching to ceph-volume simple activate which would proceed with activation.