17.7. WOL — Wake on LAN

SUSE LINUX Enterprise Server – Installation and Administration Chapter 17. Power Management / 17.7. WOL — Wake on LAN
	17.6. The YaST Power Management Module		Chapter 18. File Systems in Linux

WOL (wake on LAN) refers to the possibility of waking up a computer from standby mode over the network using special packages. This “magic packet” is received by the network card and ensures that the motherboard activates the power supply and boots the computer. The advantage of this method is that computers do not have to be switched on permanently (which saves energy), but they can be activated via WOL.

	Support for WOL
Wake on LAN only works with more recent motherboards that support this functionality in their BIOS. WOL-capable network cards mostly contain chips in the Intel i82557 (EEpro100B), i82558 (EEPro100+), or i82559 series. Further information about this is available from: http://support.intel.com/support/network/sb/cs-008459.htm. Unfortunately, a lot of hardware does not have this functionality, even though it is apparently WOL-capable. Unfortunately, there is no alternative but to try the relevant steps.

Support for WOL

Wake on LAN only works with more recent motherboards that support this functionality in their BIOS. WOL-capable network cards mostly contain chips in the Intel i82557 (EEpro100B), i82558 (EEPro100+), or i82559 series. Further information about this is available from: http://support.intel.com/support/network/sb/cs-008459.htm.

Unfortunately, a lot of hardware does not have this functionality, even though it is apparently WOL-capable. Unfortunately, there is no alternative but to try the relevant steps.

17.7.1. BIOS Configuration

Before using WOL, enable an option in BIOS that is frequently labeled OnBoard LAN or Boot from LAN. Depending on your BIOS, it can be found in the ‘OnBoard Device Configuration’, ‘Boot’, or ‘PowerSave’ menu. In case of doubt, consult the documentation for your motherboard.

Further check that your system has the latest BIOS and, if necessary, update it. Information about BIOS updates can be found on the home page of the relevant motherboard vendor.

	BIOS Updates
A BIOS update is tricky to implement. It is therefore imperative that you follow the instructions issued by your motherboard vendor, as otherwise your motherboard could become inoperable and your system could no longer start.

Older network cards (for example, 3COM) must be connected to the motherboard with a three-pin cable. On newer network cards, this procedure is no longer necessary.

17.7.2. Configuration with YaST

Start YaST as root user and select ‘Network Services’+‘WOL’. If there is a DHCP server running on your computer, the WOL module displays the existing computers on your network that you can include in your WOL list.

If a DHCP server is not running, enter the remote computers manually. Click Add and enter the host name and MAC (media access connector) address for the network card. The MAC address is unique for every network device and can be displayed with:

# ip link show eth0
2: eth0: <BROADCAST,MULTICAST,NOTRAILERS,UP> 
mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:80:c8:94:c3:e7 brd ff:ff:ff:ff:ff:ff

In Enter the MAC Address of the client:, enter the value contained in link/ether. Confirm with Save. The configuration with YaST is now complete.

17.7.3. Waking up Computers

If your computers are appropriately configured, wake them up in the WOL YaST module by clicking Wake up. The selected computer then starts.

Another option is to enter the command ether-wake from the netdiag package. With this command, a particular computer can be woken up by entering its MAC address as in ether-wake 00:80:C8:94:C3:E7. Obtain help for this command with --help or -u.

17.7.4. Further Information

Further information is available in the mini HOWTO for WOL at http://gsd.di.uminho.pt/jpo/software/wakeonlan/mini-howto/wol-mini-howto.html.