NUT installs a current list sorted by manufacturer to /usr/share/nut/driver.list consult the list and note the name of the driver required for your UPS. To configure your system, first check the model names and numbers of the UPSes you wish to monitor. As of the moment, the online documentation has not caught up to the changes since the last release (2.2), but the documentation and configuration help included in the packages is enough to go by. The newest release is version 2.4, from January of 2009. You can download NUT source code and binaries from the project’s Web site, but most Linux distributions include it through their package management systems. This separation of duties is what allows NUT to work in a networked environment a slave machine can run only upsmon and listen for power outage events from the master, and the master can connect to multiple hardware UPSes, as is the case for servers with redundant power supplies. 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. You can even configure NUT to shut down the slave devices immediately, preserving more battery power for the master, in case power is restored. 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. 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. NUT can monitor UPSes connected via serial cable or USB, and is designed for networked operation to control multiple servers and workstations. 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. For added protection, you can run a power-monitoring utility that will read status information from the UPS and perform a clean shutdown of the connected machine (or machines), preserving data and stopping processes in the proper state. But although simply connecting your PC or server to a UPS will protect you from intermittent power outages and give you the chance to shut the system down at the keyboard, an unattended power outage could still cause problems. An uninterruptible power supply (UPS) is a must-have in server environments, and for many desktop users as well.

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