[Nut-upsuser] ordered shutdown

[Arjen de Korte]

Citeren Marco Chiappero <marco op absence.it>:

>> It's funny that you mention MGE PSP here, since except for the
>> shutdown timer (reason explained in the FAQ), NUT already provides
>> *all* functionality it has (including shutdown based on charge and
>> runtime). What you may be missing is the fact that this requires
>> setting values on the UPS through the 'upsrw' command to control the
>> level when the UPS will decide the battery is low.
> As far as I remember in PSP there are two different regulations, battery
> charge level that triggers system shutdown and battery charge level that
> set the "low battery" state. I suppose it uses the first one that
> occurs. If I'm not wrong.

You're wrong. :-)

In MGE PSP you can set the equivalent what we call in NUT  
'battery.charge.low' and 'battery.charge.restart'. The first will  
determine the level that triggers the 'battery low' warning (and  
system shutdown), but the second does something completely different.

You don't want to restart your systems if there isn't sufficient  
battery charge left to cleanly shut them down. Imaging that the power  
returns, but fails after one or two minutes again (maybe the fuse that  
was replaced, blew again). In that time, the server will probably have  
restarted, but the UPS batteries will still be almost empty and there  
may not be enough time to shutdown cleanly. This is where the  
'battery.charge.restart' level comes into play. It will make the UPS  
not power up the outputs again until the battery has been recharged to  
a certain level again (which of course should be enough to do a full  
restart/power down cycle). In that case, no matter how often the mains  
fails, there will always be enough juice in the battery to shut your  
systems down cleanly.

See also what is written about this at the bottom of  
'docs/shutdown.txt'. Generally speaking, the 'battery.charge.restart'  
level should be *higher* than 'battery.charge.low' (if you understood  
the problem, you'll know why).

Best regards, Arjen
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