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+Title: Saving power with Debian Edu / Skolelinux using shutdown-at-night
+Tags: english, debian edu
+Date: 2012-02-05 09:40
+
+<p>Since the Lenny version of
+<a href="http://www.skolelinux.org/">Debian Edu / Skolelinux</a>, 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
+<a href="http://packages.qa.debian.org/s/shutdown-at-night.html">shutdown-at-night</a> Debian package.</p>
+
+<p>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
+<a href="http://packages.qa.debian.org/n/nvram-wakeup.html">nvram-wakeup</a>
+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.</p>
+
+<p>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.</p>.
+
+<p>The shutdown-at-night package is completely self contained, and can
+be used also outside the Debian Edu environment.  For those without a
+central LDAP server with netgroups, one can instead touch the file
+<tt>/etc/shutdown-at-night/shutdown-at-night</tt> to enable it.
+Perhaps you can use it to save some power too?</p>