Wake-on-LAN is a useful feature on most network cards that allows you to remotely boot up a computer.

The ethtool utility (found in the ethtool RPM) can tell you if your network card supports Wake-on-LAN:

[root@example]# ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes:   10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes:  10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Full
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: umbg
Wake-on: d
Current message level: 0x00000007 (7)
Link detected: yes`

Look for the “Supports Wake-on” line. It should list one or more letters, including “g” (WoL using Magic Packet). In the example above, Wake-on-LAN is currently disabled (“d”).

The Wake-on-LAN setting does not persist. It needs to be configured every time the machine boots. On RHEL, this is usually done from /etc/init.d. Create a script called /etc/init.d/wol with the following content:

#!/bin/bash
#
# wol          Wake-on-LAN configuration script
#
# chkconfig: - 99 01
# description: Wake-on-LAN allows a machine to be started using a WoL network packet.
#              This script configured WoL on interfaces listed in $NIC.
# processname: -
# config: -
# pidfile: -
 
# Source function library.  
. /etc/rc.d/init.d/functions
 
# List of NICs to configure for WoL.  
# Note: on Xen hosts, use peth0 instead of eth0.  
NIC=”eth0″

if [ “$1” != “start” ]; then  
    exit 0  
fi
 
echo -n “Enabling Wake-on-LAN for:”  
for nic in ${NIC}; do  
    echo -n ” ${nic}”  
    [ -x /sbin/ethtool ] && /sbin/ethtool -s ${nic} wol g >/dev/null 2>&1
done

# Note: no error checking – ethtool does not return a useful exit code  
# EOF

Add the script to the startup sequence:

chkconfig --add wol
chkconfig wol on

The script will now be run on every reboot. You can check the result using ethtool eth0; it should now display “Wake-on: g“.

You should now be able to shutdown your computer, and wake it by sending a “WoL Magic Packet” from another computer. On Linux, use ether-wake (from the net-tools RPM) or wol (from the wol RPM) to send the Magic Packet:

/sbin/ether-wake -i eth0 00:04:23:C0:FF:EE

Voila!

Updated: