[Nut-upsuser] Proxmox as secondary gets power interrupted during VM shutdown

[Shaun Currier]

Hello,

First of all, I'd like to compliment NUT on having great documentation and
hardware support!

My issue:
I am running Proxmox 6.3-3 with NUT 2.7.4-8 which was installed via apt
package.  It is connected as a secondary through a TrueNAS NUT primary that
is directly attached to an Eaton 5P750 UPS via USB.

My configuration is mostly default settings, but HOSTSYNC is set to 120.

When I trigger a shutdown event on the primary with `upsmon -c fsd`, I can
see that Proxmox correctly receives the FSD signal and starts shutting
down.  It takes a long time (~50 seconds) to shut down the guest VM's
hosted on Proxmox, though, and the process is interrupted by the power
being "cut."  Really, since I'm only manually triggering the FSD and this
isn't a real power outage, the power cut is merely assumed when the primary
fully shuts down.

Why is this happening?  Shouldn't NUT somehow know that VM's on Proxmox are
still shutting down, and not disconnect from the primary until it's very
close to the end of the shutdown process?

Is it possible that the NUT package on Proxmox does not have dependencies
to other services set correctly, i.e. the NUT service/unit should depend on
the VM shutdown unit, but it doesn't?

As a side note in case it's related, NUT's user authentication does not
seem to be enforced in my system.  I can change the password to something
erroneous for the Proxmox's NUT upsmon user, but it can still access the
NUT primary, which is unexpected.  I expect it to get denied access, but
it's not.

Thanks for any help you can provide!
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