NUT lets your Linux box shut down cleanly before the UPS battery dies
Configure a UPS on Linux with NUT
A step-by-step guide to setting up Network UPS Tools (NUT) on a single Linux machine. It covers installing the package, detecting the UPS with nut-scanner, configuring the driver, upsd, and upsmon, and testing that the system will shut down gracefully when the battery runs low. Includes troubleshooting for common permission and connection errors.
Without software monitoring the UPS, your system will still crash hard when the battery runs out.