[Nut-upsuser] UPS shutdown - always the thing to do?

Arjen de Korte nut+users at de-korte.org
Tue Nov 20 08:31:59 UTC 2007

> Now looking at the FAQ again, it offers the same snippet of code as the
> Install doc, but implies that it isn't needed just in case the bios - as
> mine does - has an "always power on when power's restored" option.
> If that implication is right, then does that mean that soon after the UPS
> gives the signal to the PC that the PC should consider shutting down, that
> the UPS will cut the power anyway - assuring a power cycle to restart the
> PC? If so, that could leave a small window between the PC's going off and
> the UPS cutting the power (when not commanded to do so prematurely with
> that
> "shutdown" command) in which power restoration wouldn't trigger the PC
> rebooting - unless the UPS is smart enough to power cycle on power
> restoration just in the case that it was past the point of advising PC
> shutdowns already. If that's so, then I should stop worrying and get back
> to
> packing for vacation.

The best answer we can offer here, is to just try it out on your specific
kind of hardware. The proof of the pudding is in the eating.

> (I'm not, btw, really expecting you know this level of detail - just
> figuring
> someone on this list probably does. The docs seem to not quite cover
> this.)

The documentation does cover this. See 'docs/shutdown.txt' which describes
exactly the problem you're picturing (under 'Power races') and also shows
a way how to test if you're vulnerable to this kind of problem (under
'Testing power races').

Best regards, Arjen
Eindhoven - The Netherlands
Key fingerprint - 66 4E 03 2C 9D B5 CB 9B  7A FE 7E C1 EE 88 BC 57

More information about the Nut-upsuser mailing list