Preparing to go asleep
To make Linux not shut down the network interface upon halt, edit the file
/etc/init.d/halt, find the line with the
halt command and remove the parameter
-i if there. This parameter does
ifdown on all networking interfaces. As the manpage for halt states, this is unneccessary for newer kernels – also it disables WOL.
The second step is to make sure, your card supports WOL. To find out, issue the
sudo ethtool eth0 command. You should get something like this:
Settings for eth0: Supported ports: [ TP MII ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full Supports auto-negotiation: Yes Advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full Advertised auto-negotiation: Yes Speed: 10Mb/s Duplex: Half Port: MII PHYAD: 1 Transceiver: internal Auto-negotiation: on Supports Wake-on: g Wake-on: g Current message level: 0x00000007 (7) Link detected: no
The important lines are the
Supports Wake-on and
Wake-on ones. The “
g” means it is enabled for MagicPacket™. If not, you should manually call the command:
ethtool -s eth0 wol g
This should enable WOL for the card. If this works, you have to issue this command after every bootup as the state will be back to disabled then. You might want to create a startup script.
Waking remote PCs
The simple way is to use
wakeonlan which only supports MagicPacket™.
For a PC in a Class C network, use a call like this:
wakeonlan -i 192.168.1.255 de:ad:be:ef:ca:fe
This would send the packet to the 192.168.1.x subnet and the PC with the specified MAC address should wake up.
Note: Some nVidia chipsets require the MAC address to be specified in reverse order. In the example this would be