Ich überwache mein NAS mit checkmk. Aber ab und zu sehe ich dann einen systemd Fehler.
root@rockpro64:/etc/systemd/system# systemctl --failed
UNIT LOAD ACTIVE SUB DESCRIPTION
● check_mk@24142-192.168.3.207:6556-192.168.3.213:59118.service loaded failed failed Check_MK (192.168.3.213:59118)
LOAD = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB = The low-level unit activation state, values depend on unit type.
1 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.
Ich habe noch keine Ahnung warum das passiert, aber ich weiß wie er wieder startet 
systemctl start check_mk@24142-192.168.3.207:6556-192.168.3.213:59118.service
Kontrolle
root@rockpro64:/etc/systemd/system# systemctl --failed
0 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.
Alles wieder gut
FrankM