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

Mark E. Hansen meh at Winfirst.Com
Mon Nov 19 21:07:59 UTC 2007

On 11/19/07 12:46, Whit Blauvelt wrote:
> Hi,
> In an instance where the system is in a sometimes-unattended facility, are
> there different implications to shutting down the UPS from a script, as
> compared to not doing so? My goal is to have systems recover ASAP when the
> power comes back. My UPS is a Cyberpower 1500AVR. The two servers connected
> to it boot fine when power is restored to them. But I'm ignorant on how the
> UPS itself will behave. If shut down, do UPS's as a rule turn on when power
> comes back? Or does that depend on the model? 
> Is there an argument for not shutting the UPS down, just in case power comes
> back before it's run out of battery even to sustain even its own state?
> Thanks,
> Whit

I'm not a UPS expert (or NUT for that matter), but just went through all this
with my CyberPower AVR1200 connected to a Linux machine.

First, I assume that you have the NUT package configured such that when the
line power fails, the UPS will cause the PC to shutdown. If you allow the
PC to shut all the way down, then it likely won't boot back up when the line
power returns.

What you need to do is to tell the UPS to kill the power to the PC just before
the machine completes the shutdown sequence. This way, your machine's shutdown
scripts will be able to do everything they need to do, like kill all the
applications, sync the drives, etc., and then tell the UPS to kill the power
to the PC.

Because the PC's shutdown script tells the UPS to kill the power to the PC, the
PC's BIOS thinks the PC was "up" when it's power failed. Then, once line power is
returned to the UPS, it will restore power to the PC, and the PC will boot up as

Unfortunately in my case (CentOS 4.5) I had to do a fair amount of twiddling
with my machine's shutdown script (/etc/init.d/halt) to get it to do this. It
certainly didn't work "out of the box".

Let me know if you have any questions, as I may not have understood your

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