[Nut-upsuser] Getting the UPS to cut power to the PC at the right time

[Arjen de Korte]

[...]

> I think this is probably a problem that is specific to USB connections
> only, as the serial communications would likely not be effected by
> the operations carried out in the shutdown processing? Not sure about
> that though.
>
> My solution was to hijack each of the sections in the 'halt' script
> that were unmounting file systems (and/or mounting them as read only),
> and skipping these operations for the "/proc" and "/proc/bus/usb"
> file systems if the "/etc/killpower" file exists. Basically leaving
> "/proc" and "/proc/bus/usb" mounted read/write.

There is no need to unmount /proc or anything below it, since this is
stored in (volatile) memory. As there is no risk of trashing this
filesystem on shutdown, it would be safe to leave it mounted as it is with
or without a /etc/killpower flag.

> If this is typical of a USB installation, I wonder if others might
> benefit from a README or FAQ entry explaining the above?

It is probably typical for CentOS and as such it would probably be helpful
to write a FAQ entry for it. Better yet, convince CentOS that they don't
need to unmount /proc, so that it doesn't need fixing (and a FAQ entry) in
the first place.

Best regards, Arjen
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