I’ve attached a UPS to my server through USB. and sure enough up came a tab in Power Management Preferences for the UPS – great.
There are power low options as follows:
“When UPS power is low”
“When UPS power is critically low”
The UPS sends a message to the computer when a threshold you set in the UPS is reached, in my case 25% of battery left.
The obvious guess is that this warning from the UPS is the “When UPS power is low” however, I don’t know. It’s just a guess.
Looking further at the data I can get from the UPS the battery data is as follows:
The obvious relationships here are:
“When UPS power is low” -> battery.charge.warning
“When UPS power is critically low” -> battery.charge.low
However, again, that’s just a guess from what would make sense.
So my first question is, is there a way to know this information, and is there a place were these critical points are set, or are they all from the UPS. I’m guess there are some settings somewhere because not all UPSs are going to be able to supply this information. Some may only supply a battery level or some just a warning message so there must be some configuration for this somewhere.
My 2nd question is a probably a little harder to know the answer to. After getting this to work I wanted the added functionality of nut so I installed it and got it working and it uses the On UPS Power panel as far as I can tell.
Through all the nut documentation it talks about powering down on once the battery level reaches the critical point (I assume that is “When UPS power is critically low”). I don’t see anywhere however where it mentions handling “When UPS power is low” so now the question comes up, will it have any effect at all with nut installed, i.e. what will happen?
Of course I can just “pull the plug” and start finding this stuff out but Linux is all about having the information and “knowing” (assuming all works as it should) I am asking to find out where this information would be – and become smarter for it