This simple project describes building a low-powered embedded Linux system to find and shut down idling Linux and Windows PCs left on by careless, energy-wasting users. Suitable for deployment on a Linksys WRT54G or NSLU2, it leverages the open source Argus network monitoring tool, along with custom perl scripts.

The project was put together by Nathan Harrington, and published on IBM's DeveloperWorks website. It uses the server portion of the open source Argus network monitor (not to be confused with the argus monitor) to tally up packets from each system. Calling an argus client (racluster, in this example), a perl script reads the tallies at intervals, and compares the level of activity against a set threshold established in advance for each machine. When the threshold is exceeded, the perl script contacts the idling machine and shuts it down. The perl-based “listener” script running on the client side uses challenge and response, with Blowfish encryption, to authenticate the request before calling shutdown.

For large networks, a device with multiple Ethernet connections would work best, Harrington said. Left as an exercise to the reader are code additions to shut down systems that are only fetching mail every 15 minutes, and muted systems endlessly downloading media streams. Harrington offers no suggestion for handling complaints from users who lose unsaved work, however. The full story, complete with code downloads, can be found here.

 
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