cat /usr/lib/systemd/system/ceph-mon@.service
[Unit]
Description=CephFS MON %i
Requires=network.target
After=network.target

[Service]
Type=simple
Restart=always
RestartSec=2s
ExecStart=/usr/bin/ceph-mon -f -i %i

[Install]
WantedBy=multi-user.target