Petter Reinholdtsen

Saving power with Debian Edu / Skolelinux using shutdown-at-night
5th February 2012

Since the Lenny version of Debian Edu / Skolelinux, a feature to save power have been included. It is as simple as it is practical: Shut down unused clients at night, and turn them on again in the morning. This is done using the shutdown-at-night Debian package.

To enable this feature on a client, the machine need to be added to the netgroup shutdown-at-night-hosts. For Debian Edu, this is done in LDAP, and once this is in place, the machine in question will check every hour from 16:00 until 06:00 to see if the machine is unused, and shut it down if it is. If the hardware in question is supported by the nvram-wakeup package, the BIOS is told to turn the machine back on around 07:00 +- 10 minutes. If this isn't working, one can configure wake-on-lan to try to turn on the client. The wake-on-lan option is only documented and not enabled by default in Debian Edu.

It is important to not turn all machines on at once, as this can blow a fuse if several computers are connected to the same fuse like the common setup for a classroom. The nvram-wakeup method only work for machines with a functioning hardware/BIOS clock. I've seen old machines where the BIOS battery were dead and the hardware clock were starting from 0 (or was it 1990?) every boot. If you have one of those, you have to turn on the computer manually.

The shutdown-at-night package is completely self contained, and can also be used outside the Debian Edu environment. For those without a central LDAP server with netgroups, one can instead touch the file /etc/shutdown-at-night/shutdown-at-night to enable it. Perhaps you too can use it to save some power?

Tags: debian edu, english.

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