I just updated one of my servers and it failed to reboot.
The reason is that I had:
Requires=node_exporter.service
in the default target and the update had installed a change to
the name of the node exporter service. It is not called
prometheus-node-exporter.service
Having been bitten I'm changing to use:
Wants=prometheus-node-exporter.service
Just incase it changes again.
Barry