Features

Monitors many UPS, PDU, ATS, PSU and SCD models from more than 170 manufacturers with a unified interface (Hardware Compatibility List).

Various communication types and many protocols are supported with the same common interface:

Cross-platform — different flavors of Unix can be managed together with a common set of tools, even crossing architectures.

This software has been reported to run on Linux distributions, the BSDs, Apple’s OS X, commercial Solaris and open-source illumos distros, IRIX, HP/UX, Tru64 Unix, and AIX.

Windows users may be able to build it directly with MSYS2, MinGW or Cygwin. There is also a port of the client-side monitoring to Windows called WinNUT.

Your system will probably run it too. You just need a good C compiler and possibly some more packages to gain access to the serial ports. Other features, such as USB / SNMP / whatever, will also need extra software installed.

Three layers: drivers, server, clients.

Drivers run on the same host as the server, and clients communicate with the server over the network.

This means clients can monitor any UPS anywhere as long as there is a network path between them.

upsmon can handle high-end servers which receive power from multiple UPSes simultaneously.

upsmon won’t initiate a shutdown until the total power situation across all source UPSes becomes critical (on battery and low battery).

You can lose a UPS completely as long as you still have at least the minimum number of sources available. The minimum value is configurable.

Manager functions are granted with per-user granularity. The admin can have full powers, while the admin’s helper can only do specific non-destructive tasks such as a battery test (beware that with a worn-out battery whose replacement is a few years overdue, a "capacity/remaining runtime" test can still be destructive by powering off the load abruptly — and also such a test can cause hosts to hide into graceful shutdowns when the battery state does get critical as part of the test).

The drivers, server, and monitoring client (upsmon) can all run as separate user IDs if this is desired for privilege separation.

Only one tiny part of one program has root powers. upsmon starts as root and forks an unprivileged process which does the actual monitoring over the network. They remain connected over a pipe. When a shutdown is necessary, a single character is sent to the privileged process. It then calls the predefined shutdown command. In any other case, the privileged process exits. This was inspired by the auth mechanism in Solar Designer’s excellent popa3d.

The drivers and network server may be run in a chroot jail for further security benefits. This is supported directly since version 1.4 and beyond with the chroot= configuration directive.

IP-based access control relies on the local firewall and TCP Wrapper.

SSL is available as a build option ("--with-ssl"). It encrypts sessions with upsd and can also be used to authenticate servers.

Comes stock with CGI-based web interface tools for UPS monitoring and management, including graphical status displays.

Custom status web pages may be generated with the CGI programs, since they use templates to create the pages. This allows you to have status pages which fit the look and feel of the rest of your site.

That’s free beer and free speech. Licensed under the GNU General Public License version 2 or later.

Know your systems — all source code is available for inspection, so there are no mysteries or secrets in your critical monitoring tools.

Writable variables may be edited on higher end equipment for local customization

Status monitoring can generate notifications (email/pager/SMS/…) on alert conditions

Alert notices may be dampened to only trigger after a condition persists. This avoids the usual pager meltdown when something happens and no delay is used.

Maintenance actions such as battery runtime calibration are available where supported by the UPS hardware.

Power statistics can be logged in custom formats for later retrieval and analysis

All drivers are started and stopped with one common program. Starting one is as easy as starting ten: upsdrvctl start.

For operating systems with a supported service management framework, you can manage the NUT drivers wrapped into independent service instances using the upsdrvsvcctl instead, and gain the benefits of automated restart as well as possibility to define further dependencies between your OS components.

Shutdowns and other procedures may be tested without stressing actual UPS hardware by simulating status values with the dummy-ups pseudo-driver. Anything that can happen in a driver can be replicated with dummy-ups.