C[omp]ute

From: andrew cooke <andrew@...>

Date: Tue, 22 Sep 2009 19:49:40 -0400

I have a small, low powered computer (VIA C7 chip) that runs as a
firewall.  My work machine only runs when I'm working (this makes the
office quieter and cuts our electric bill by 25%).  But sometimes it's
nice to use my work machine even when I'm elsewhere.  Until now, I had
to leave it running, but I just worked out how to start it via the
network.

The technology is called Wake On Lan (WOL), and it was fairly easy to
get working.

First, I had to enable it on my motherboard.  This is an Asus P5Q and
the option to enable is under "Power", then "APM Configuration" - it's
the line "Power on By PCI Devices" and the help text mentions PME,
which is another name for WOL.

That's all that's needed on the motherboard (this will, when working,
start from "power off" - you don't need to use suspend), but the
option must also be enabled from within Linux.  This needs to be set
on each boot and is then saved when next powered down.

Interactively, the configuration can be done with "ethtool" using the
"wol g" argument, but it makes more sense to automate this.

Because this is a desktop machine I use the "traditional" ifup
scripts, rather than network manager.  These scripts are configured in
/network/ifcfg-ethX.cfg (where X is typically 0 or 1) - change the
ETHTOOL_OPTIONS so it is equal to 'wol g'.  That automates the calling
of ethtool.

It's also worth nothing the mac address (from "ifconfig") at this
point, because that is needed to wake the computer.

Once the configuration is done, and computer powered off, all that is
needed is to run the "wol" command from another computer on the same
network, using the MAC address.  In my case I use the low-powered
server and the command is:
  wol -h 10.255.255.255 00:01:02:03:04:05
(but with the correct MAC address at the end).  The "-h
10.255.255.255" makes sure that the message is sent to the right
network (because that computer is a firewall it has two network cards)
- most people won't need that.

(For some reason the computer needs to "sit" for a moment (less than a
minute) after power off before this works, so be patient).

The driver for the network card is etl1, but that's pretty much
irrelevant (it needs to work with ethtool correctly).

For more info see:
http://woelfisch.livejournal.com/94245.html
http://ubuntuforums.org/showthread.php?t=234588

Andrew