High Quality Content by WIKIPEDIA articles! Apcupsd (the name stands for APC UPS Daemon) is an application that runs on Linux, UNIX, Mac OS X and some Windows machines (using Cygwin). It allows the computer to interact with (almost all recent) APC Uninterruptible power supplies (UPS). Apcupsd also works with some OEM APC power supplies (e.g., Hewlett-Packard`s).