Smart Power Monitoring with Network UPS Tools

“NUT Basics
The premiere UPS monitoring tool on Linux is Network UPS Tools
(NUT), a free software tool that supports hundreds of UPS models
from a wide range of vendors. NUT can monitor UPSes connected via
serial cable or USB, and is designed for networked operation to
control multiple servers and workstations.

“Since the vast majority of UPSes include only one USB or serial
connection, NUT can be configured to run in “slave” mode, listening
on a TCP port for a shutdown notice from the directly-connected
computer. That way, you can connect your primary server to the UPS
with the cable in “master” mode, but ensure that other devices —
such as a workstation, firewall, or NAS box — receive the message
that power is out and shut down cleanly. You can even configure NUT
to shut down the slave devices immediately, preserving more battery
power for the master, in case power is restored.

“NUT consists of three main pieces: the drivers that interface
with the actual UPS hardware, decoding its status and reports to
determine whether power is present and how much battery charge
remains, the upsmon client that monitors UPS status and responds to
power events by logging, sending notification messages, and
shutting down the system when needed, and the upsd daemon that
passes information between upsmon and the various drivers.”

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