Nut upsdev - Sep 2024 - Weekend Puzzle: computer posing as an UPS

Cheers all,

  I am experimenting with a Raspberry Pi, and it is fed from my PC
(Debian-ish Linux) that is in turn protected by an UPS - so runs NUT.

  As far as the Pi is concerned, the bigger computer is its wall power
source (provides the USB socket) and being a smart machine with NUT
running, it could pose as an UPS itself. That is, if the big computer is
going to shut down (including probably rebooting, as I expect the
motherboard to power-cycle its USB ports), it should issue FSD on some
bare-bone driver *AND* wait for clients (like upsmon running on the Pi) to
disconnect before proceeding with its own power-off/reboot.

  Did anyone already solve something like this with a custom driver or
smart use of dummy-ups vs. systemd, etc.? Probably not a hard puzzle, but
still a fun one - and if someone has already navigated the hidden troubles
and can share - so much the better :)

Jim Klimov
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Jim Klimov via Nut-upsuser <nut-upsuser at alioth-lists.debian.net>
writes:
>   I am experimenting with a Raspberry Pi, and it is fed from my PC
> (Debian-ish Linux) that is in turn protected by an UPS - so runs NUT.
>
>   As far as the Pi is concerned, the bigger computer is its wall power
> source (provides the USB socket) and being a smart machine with NUT
> running, it could pose as an UPS itself. That is, if the big computer is
> going to shut down (including probably rebooting, as I expect the
> motherboard to power-cycle its USB ports), it should issue FSD on some
> bare-bone driver *AND* wait for clients (like upsmon running on the Pi) to
> disconnect before proceeding with its own power-off/reboot.
Wow, I never would have guessed that this is a workable approach
(running the Pi this way not the nut part).   Do you have ports that are
more than 500 mA, and does the Pi (pi0?) really work with 5V 500 mA?