Wake-on-LAN (WOL) is an Ethernet networking standard that allows a server to be turned on by a network message. You need to send ‘magic packets’ to wake-on-lan enabled ethernet adapters and motherboards, in order to switch on the called systems. Make sure you connect the NIC (eth0 or eth1) with the motherboard, and enable the WOL function in the BIOS. This is a quick guide to enable WOL under RHEL / Fedora / CentOS / Debian / Ubuntu Linux.

Client Software

You need to use software to send WoL magic packets. You will find various tools for all modern oses, including MS-Windows, Apple OS X, Linux, and many smart phones.

Linux Install etherwake Under Debian / Ubuntu Linux

etherwake command can be used to send a Wake-On-LAN “Magic Packet” under Linux operating systems. Type the following command to install the same under Debian / Ubuntu Linux desktop:
$ sudo aptitude install etherwake
Sample outputs:

[sudo] password for vivek:
The following NEW packages will be installed:
  etherwake wakeonlan{a}
0 packages upgraded, 2 newly installed, 0 to remove and 11 not upgraded.
Need to get 20.9 kB of archives. After unpacking 98.3 kB will be used.
Do you want to continue? [Y/n/?] y
Get:1 http://mirror.anl.gov/debian/ squeeze/main etherwake amd64 1.09-3 [9,564 B]
Get:2 http://mirror.anl.gov/debian/ squeeze/main wakeonlan all 0.41-10 [11.4 kB]
Fetched 20.9 kB in 2s (10.3 kB/s)
Selecting previously deselected package etherwake.
(Reading database ... 195338 files and directories currently installed.)
Unpacking etherwake (from .../etherwake_1.09-3_amd64.deb) ...
Selecting previously deselected package wakeonlan.
Unpacking wakeonlan (from .../wakeonlan_0.41-10_all.deb) ...
Processing triggers for man-db ...
Setting up etherwake (1.09-3) ...
Setting up wakeonlan (0.41-10) ...

Note: Red Hat Linux and friends user should use net-tools package which is installed by default.

How Do I Send WOL Magic Packets Under Linux?

Type the following command:
# wakeonlan MAC-Address-Here
OR
# etherwake MAC-Address-Here
# etherwake -D MAC-Address-Here
RHEL / Centos / Fedora Linux user, try:
# ether-wake MAC-Address-Here
If your MAC address were xx:yy:zz:11:22:33, you would type:
# wakeonlan xx:yy:zz:11:22:33
OR
# etherwake xx:yy:zz:11:22:33
Where,

• xx:yy:zz:11:22:33 is remote servers mac address. You can obtained mac address using combination of ping and arp command – ‘ping -c 4 server3 && arp -n‘.

How Do I Verify That Remote Linux Server Supports Wake-on-LAN (WOL)?

First, reboot the remote server and go to BIOS > Power Management > “Wake On LAN”. Turn it on. Next, save and close the bios. After activating Wake On LAN in hardware (BIOS) it is also necessary to activate it using ethtool. The ethtool will configure eth0 to respond to the magic packet:
# ethtool -s eth0 wol g
Where,

1. -s eth0 : Your NIC. Feel free to replace eth0 with your actual network interface device name.
2. wol g : Sets Wake-on-LAN options using MagicPacket.

Type the following command to see current status of wol for eth0:
# ethtool eth0
Sample outputs:

Settings for eth0:
	Supported ports: [ ]
	Supported link modes:
	Supports auto-negotiation: No
	Advertised link modes:  Not reported
	Advertised auto-negotiation: No
	Speed: 100Mb/s
	Duplex: Full
	Port: MII
	PHYAD: 1
	Transceiver: internal
	Auto-negotiation: off
        Supports Wake-on: g
       Wake-on: g
	Link detected: yes

If you are using RHEL / SL / Fedora / CentOS Linux, edit /etc/sysconfig/network-scripts/ifcfg-eth0:
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
Add / modify the following line:

ETHTOOL_OPTS="wol g"

OR

ETHTOOL_OPTS="wol g autoneg off speed 100 duplex full "

Save and close the file. If you are using Debian / Ubuntu Linux, edit /etc/network/interfaces:
# vi /etc/network/interfaces
Append the following to eth0:

auto eth0
iface eth0 inet static
address 192.168.1.1
netmask 255.255.255.0
gateway 192.168.1.254
        post-up /sbin/ethtool -s eth0 wol g
        post-down /sbin/ethtool -s eth0 wol g

Recommend readings

• man pages – ethtool, ether-wake / etherwake, arp, wakeonlan
• Wake-on-LAN