For some variety I occassionally install FreeBSD. However, I couldn’t find any UPS control software that fit my needs. So I studied the sources of various Linux centric UPS daemons such as genpowerd and powerd. TinyUPS Daemon is what I call the result of my efforts.

An Uninterruptible Power Supply is required. Any UPS supporting dumb signalling should work but it has only been tested with an APC Back-UPS and the cable shown.

* UPS Side                           Serial Port Side
* 9 Pin Male                         9 Pin Female
* Shutdown UPS 1 <---------------> 3 TX  (high = kill power)
* Line Fail    2 <---------------> 1 DCD (high = power fail)
* Ground       4 <---------------> 5 GND
* Low Battery  5 <----+----------> 6 DSR (low = low battery)
*                     `---|  |---> 4 DTR (cable power)

The project is hosted on GitHub.

Install by cloning the git repo

git clone

Install by downloading the latest tarball at tinyupsd tarball