====== Wake-on-LAN ======

Wake-on-LAN (or WOL) is a standard by which a machine can be powered on remotely via a network connection. This is done by sending a so-called //magic packet// to the network card of the remote machine. When properly configured, the remote machine will then boot. 

<note> Most recent desktop computers support this, but it will likely be switched off by default. On very old machines, you may need to run a special cable from the network card to the motherboard.</note>

===== Configure the BIOS =====
The Wake-on-LAN option must be enabled in the BIOS. Unfortunately these settings are not standardized. Check the motherboard documentation. Browse the BIOS menu. The option may not be called Wake-on-LAN, but something like 'Power On By PCI Device'. This varies greatly from board to board and some experimentation may be needed. 

===== Configure the network card =====
Assuming the first network port is connected, use ''ethtool'' to check the card settings:
<code>
# ethtool eth0 | grep -i wake-on
    Supports Wake-on: pg
	Wake-on: d
</code>
The //supports// line shows all options that are supported on the card. The option to look for is **g**, which means wake on magic packet. If the g option is not present, you are out of luck. 

The //Wake-on// line shows the current options in use. If this shows **d**, it means wake-on is currently disabled. 

To enable wake-on, use 
<code>
# ethtool -s eth0 wol g
</code>

This will most likely not survive a reboot, so to switch this option on again at the next boot, add the command to ''/etc/rc.d/rc.local'':
<file - rc.local>
echo "Setting Wake-on-LAN to Enabled"
/usr/sbin/ethtool -s eth0 wol g 
</file>

Finally, we need to note the MAC address of the network card we just prepared: 
<code>
# ip addr show eth0 | grep -i ether 
    link/ether 20:cf:30:1f:e3:a4 brd ff:ff:ff:ff:ff:ff
</code>

===== Waking up the machine =====
Now we need a special command on a different machine to send a magic packet. The ''wol'' command is available from [[http://slackbuilds.org|slackbuilds.org]]. This can be called by a regular user. At a minimum it needs the MAC address of the remote machine; for example: 
<code>
$ wol 20:cf:30:1f:e3:a4
</code>

On a multihomed host, like a router, use the //host// option to specify the hostname or ip address of the remote host. This will broadcast the magic packet on the correct subnet:
<code>
$ wol -i hostname 20:cf:30:1f:e3:a4
</code>




====== Sources ======
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  * Originally written by [[wiki:user:fdonkers | Frank Donkers]] 
<!-- * Contributions by [[wiki:user:yyy | User Y]] -->

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{{tag>howtos wol wake author_fdonkers}}