Monitor does not shutdown ups if MODE in /etc/nut/nut.conf is not set

[BlackZork]

After upgrade from 2.8.2 to 2.8.4 nut stopped to shutdown my UPS on nut initiated OS shutdown.

After debugging it turns out I did not change MODE=none in nut.conf after this change: cccbd87

Consider adding a warning at least in nut-monitor service, or exit nut-monitor with error code if MODE is not set.

[jimklimov]

I think this is already covered in #3233 - that the daemons would not start if MODE does not have a known-unsuitable value (so with other values, including absent/empty, they would start). It would be part of NUT v2.8.5 release eventually (hopefully soon).

[jimklimov]

Updated the FAQ with a note on this nuance.