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My server that runs apcupsd is the largest load on my UPS, and whenever the power goes out I want to have the server shutdown and leave the UPS to run until the UPS shuts itself down on low battery voltage. (Note that this will not harm any of the affected devices powered by the UPS.)

However, I'm not sure which directive is best to set this with.

The closest I can figure is that setting SLEEP to some really huge number would leave the UPS running until it is forced to shut down, but I'm unclear if this will achieve the desired results of simply running the UPS until it shuts down because of the low battery, or will the UPS attempt to run in an unsafe condition (e.g. output voltage too low)?

The apcupsd version is 3.14.10 (from the Ubuntu 12.04 main repository).

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The UPS output should be regulated, and its either going to be at the specified/configured voltage, or at 0. It shouldn't run at a lower voltage (other than 0), no matter how low the batteries get. If the UPS runs out of power before the sleep time expires... it just turns off.

Note that deeper discharges will mean more frequent battery replacements.

Anyway, I personally use NUT, but looking at the apcupsd manual, it appears you just want to remove the apccontrol killpower from your shutdown scripts (or the --kill-on-powerfail option from the daemon command line).

Note that killpower is there for a reason; in particular:

  1. Power goes out
  2. Battery gets low
  3. Server starts shutting down
  4. Power comes back

In this case, power will never drop, so the server will be left shut down. With killpower, you get the extra step of the UPS cycling off the output (yes, its supposed to, even with line power) so the server will boot back up.

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