View Source: WakeOnLanNotes - Waikato Linux Users Group

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Prerequisites for WakeOnLan:

* A motherboard aware of resume on ring events
* A [NIC] with WakeOnLan support
* Possibly a cable connecting the [NIC] to the [WOL] header on your motherboard (unless it's an onboard [NIC])

You will need to enable WakeOnLan in the machine's [BIOS], and you will need to know the [NIC]'s [MAC] address.

From another machine you can then use [ether-wake | http://www.scyld.com/wakeonlan.html] to send the special [Ethernet] frame:

<pre>
$ ether-wake ''$[MAC]ADDRESS''
</pre>

If you add an entry mapping [MAC] addresses to hostnames to <tt>/etc/ethers</tt>, you will also be able to simply say

<pre>
$ ether-wake <hostname>
</pre>

Pre-compiled packages of <tt>ether-wake</tt> exist for most LinuxDistribution~s. In [Debian], it's called <tt>etherwake</tt>, but the version available in [Woody] doesn't seem to support <tt>/etc/ethers</tt>.

Some [Linux] [NIC] drivers seem to disable the WakeOnLan function of the network card. If you can use WakeOnLan after booting into Windows, but not at all after booting into Linux, your driver is probably one of them. [ethtool | http://gkernel.sf.net/] allows you to change this. An initial query of an interface's properties will look something like this:

<verbatim>
$ ethtool eth0
Settings for eth0:
       Supports Wake-on: g
       Wake-on: d
       Link detected: yes
</verbatim>

Here, MagicPacket (type g) WakeOnLan support is available but disabled (Wake-on: d). You can change this with a swift

<verbatim>
$ ethtool -s eth0 wol g
</verbatim>

This time, a query to confirm the result should produce something like this output:

<verbatim>
$ ethtool eth0
Settings for eth0:
       Supports Wake-on: g
       Wake-on: g
       Link detected: yes
</verbatim>

Note that you'll need to change the setting anew on every boot, so stick the command in <tt>rc.local</tt> or whichever boot script is applicable.

If you encounter further problems check the parameters passed to the halt command in your shutdown script (/etc/init.d/shutdown.sh on gentoo).
The -i parameter tells halt to down all the network interfaces just before shutdown which will prevent wol from working.

----

! Which open ports do you need to open for ether-wake?

First of all, you normally use ether-wake to trigger a wake-on-lan event on a powered off computer. It is unlikely to have a firewall running at this point!.

ether-wake works by sending a special ethernet frame. Read the notes at MagicPacket for more information about this.  Because this is an ethernet frame, and not actually an IP packet, it is not routable. The answer to the above question is "You can't".

There are other types of wake-on-lan triggers however, and I believe the only requirement is that it follows the format specified in the MagicPacket notes. these may or may not IP packets, and whether you need to open firewalls up to them or not will depend entirely on the local configuration.
4 pages link to WakeOnLanNotes:
Last edited on Wednesday, September 14, 2005 11:23:20 am by "ToniMarsh"
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