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

Arjen de Korte nut+users at de-korte.org
Tue Nov 20 12:47:05 UTC 2007

>> 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.
> Of course. The shortcoming being that running the UPS down that far would
> take a few hours - at which point I start thinking asking around might be
> more efficient use of time, just in case somebody knows, since really
> proving the pudding might take multiple cycles of full discharge-recharge,
> plus it's production equipment hanging on it I don't want to keep shutting
> down.

It is not needed to run the batteries to empty. In order to try this out,
you can 'fake' an OB+LB situation by issuing the 'upsmon -c fsd' command
(this is also documented in 'docs/shutdown.txt' and the manual page for
upsmon). Once with the mains present (to test a power race) and once
without (to make sure the UPS doesn't restart on battery). If both of
these are passed, it is still a good idea to run the UPS on battery until
it signals OB+LB by itself. Sometimes the remaining time on battery is too
short for an orderly shutdown of your systems and you certainly don't want
to be surprised by that when you're not around.


> To another reply - it's the "cyberpower" driver that works with the
> 1500AVR.
> (The more modern driver skews the values badly. I requested the right
> conversions from the manufacturer, but the rep who responded regretted
> that he couldn't get the tech staff to reveal those.)

We already have (more or less) the conversion values that are needed.
Problem is that we don't know when to apply these, as some devices seem to
need them, while others don't. You could help us here by posting the full
output of 'upsc' for your UPS.

> Am I right that on average, presuming a professional-level UPS (this
> sucker at least is a rack-mount with a few hours of battery in it), and
> with PCs with bioses which will can be set to boot on any fresh power
> application, that I'm better off without sending "shutdown" to the UPS?

Not at all. In that case, you'd be vulnerable to power races (see the
aforementioned document). This has really nothing to do with the BIOS in
the PC, but rather with the fact that once we initiate a shutdown sequence
in NUT, there is no way back anymore. As soon as the shutdown sequence is
started, the only way to resume normal operation is to reboot the machine.
This is what the shutdown command will do.

Best regards, Arjen

More information about the Nut-upsuser mailing list