Short version: is it possible with systemd to have the machine halt,
wait for a few minutes and then reboot?
Many UPS-es do not support cutting power at all, or ignore the command
to cut the power in certain situations. There was a workaround for that:
instead of powering the machines off, they had to halt, then wait a
reasonable amount of time (during which the UPS should turn off), and
then reboot - in case power came back and the UPS did not power-cycle
Now that systemd manages the shutdown procedure, I don't know if it's
possible to achieve the same behaviour (and thus make NUT work with
systemd). But since it's systemd, maybe we can make this even better!
There were some concerns that it's not a good idea to simply "halt the
system"; what we should do is flush all the drives' cache and unload
their heads, which can only be done *properly* from the kernel. (See
this old Debian bug:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=358696 ) So maybe with
systemd, we can actually not simply "halt" the system, but make all the
necessary preparations in order to ensure that cutting power is safe?
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