HOW-TO:Set up Wake-on-LAN for Ubuntu

If you are not one of the lucky ones with a built-in start-up controller (so that the remote can be used to start the computer) or if the computer is in the other room/floor, sometimes it's pretty annoying to go to the upstairs, for example, just to push a button. Wake-On-LAN is a network standard, which provides the ability to switch on remote computers through special network packets, called MagicPacket from sleeping, hibernating, or powered-off state. It only works with WOL compliant BIOS and NIC.

Before we start

First off, the motherboard should support the WOL (Wake On LAN) and it should be enabled in the BIOS. Different BIOS/motherboard do it differently; on ASUS (P5N7A-VM), it's under Power > APM Configuration and in there "Resume On PCIE Wake" and "Resume On LAN(MAC)" should be enabled.

Enabling WOL in the OS

Even though WOL works in network layer 2, OS support is still one of the important things to make it work. Even if you see the light on the Ethernet port is on after the halt/shutdown, the OS shuts off the Ethernet internally. One must tell Ethernet controller to WOL when boots up and tell "halt" script not to bring down controller during shut-down.

Install ethtool

I found "ethtool" is one of the easiest to use to enable WOL; install it first if it's not there yet.

sudo apt-get install ethtool

Set Wake-on-LAN options

Run the following command to enable it:

sudo ethtool -s eth0 wol g

• Note: Not all devices support this.

This can be verified running ethtool on ethX (where X is the name/number of the Ethernet device).

sudo ethtool eth0

You should see something like this ("g" indicates Wake on MagicPacket is enabled):

Settings for eth0:
	Supported ports: [ MII ]
	Supported link modes:   10baseT/Half 10baseT/Full 
	                        100baseT/Half 100baseT/Full 
	                        1000baseT/Full 
	.....
        .....
	Auto-negotiation: on
	Supports Wake-on: g
	Wake-on: g
	Link detected: yes

Get it enabled at system start-up

Debian/Ubuntu uses Sys-V like init system for executing commands during the system bootup and shutdown time. If you wish to add a new service to start when the machine boots the script should be added to the directory /etc/init.d/ and then the "/etc/rc{runlevel}.d/" symlinks cause the script to be executed.

The init.d script

Create a file, say "wake-on-lan" in the "/etc/init.d/" (just copy & paste the entire code in the terminal)

sudo cat << EOF >> /etc/init.d/wake-on-lan
#!/bin/bash
#
### BEGIN INIT INFO
# Provides:             wake-on-lan
# Required-Start:       \$local_fs
# Required-Stop:        \$local_fs
# Default-Start:        2 3 4 5
# Default-Stop:         0 6
# Short-Description:    Enable Wake-On-Lan 
### END INIT INFO
#
. /lib/lsb/init-functions

do_start() {
    ethtool -s eth0 wol g
    exit
} 

do_stop() {
    ethtool -s eth0 wol d
    exit
}

case "\$1" in
  start)
        do_start
        ;;
  restart|reload|force-reload)
        echo "Error: argument '$1' not supported" >&2
        exit 3
        ;;
  stop)
        do_stop
        ;;
  *)
        echo "Usage: $0 start|stop" >&2
        exit 3
        ;;
esac
EOF
sudo chmod 755 /etc/init.d/wake-on-lan

Automatic start-up at boot

"sysv-rc-conf" is run-level configuration for Sys-V like init script links. From the man page: sysv-rc-conf gives an easy to use interface for managing "/etc/rc{runlevel}.d/" symlinks. sysv-rc-conf is not installed by default and needs to be installed first.

sudo apt-get install sysv-rc-conf

and when done, we enable the wake-on-lan service for runlevel 2,3,4 & 5, using --level option

sudo sysv-rc-conf --level 2345 wake-on-lan on

If everything goes well, you should see the WOL is enabled for the above run-levels.

xbmc@htpc:~$ sysv-rc-conf --list | grep wake
wake-on-lan  2:on	3:on	4:on	5:on

That's all, the machine is now ready to be waken-up by WOL magic packet.

Extra info

Wake-on-LAN is platform-independent; any application that sends "magic packets" can wake up computers from shutdown state (as long mains power is not off) regardless of OS it boots into afterward. There are a number of tools available for Windows in the net. I use this script to create a magic-packet from Linux. The "node_lst" section (at the top of the script) should be modified to reflect actual MAC address of the machine in question. Put the script in the "/usr/local/bin" and change the permission to 775, so that it can be called from any where without specifying the actual path.

The script: wake-on-lan

sudo vi /usr/local/bin/wake-on-lan

Use any editor you are comfortable with to use and then copy & paste the script below.

exec /usr/bin/python -x "$0" "$@"
# -*- coding: ISO-8859-15 -*-
#
# wake-on-lan
# $Id: wake-on-lan.cin,v 1.0 2010/02/20 15:05:42 das Exp $
# S. Das, London

## --- Local nodes -------------------------- ##
## Modify this to put your own hostname/MAC 
## address pair here. The format is:
## "abc xx:xx:xx:xx:xx:xx", where "abc" could
## be any name you like and the "xx:xx..." is
## the MAC address of the machine the magic
## packet is going to be sent. 
  
node_lst = [
	'pcbk 00:18:8b:c9:29:73',
	'htpc 00:24:7c:a2:e4:d0'
]

## --- don't change anything below --------- ##

import os,sys,string,commands
import struct, socket
import re,random

retval = 0

X = '([a-zA-Z0-9]{2}[:|\-|.]?){5}[a-zA-Z0-9]{2}'
S = re.compile(r'\s+')

mmap = {}

## First argument 'None' in str.translate is new in 2.6. 
## Previously, it was a string of 256 characters.
if sys.version_info < (2, 6):
    f1_arg = ''.join(chr(i) for i in xrange(256))
else:
    f1_arg = None

def WakeOnLan(mac_address):
    
    ## Building the Wake-On-LAN "Magic Packet"...
    ## Pad the synchronization stream.
    data = ''.join(['FFFFFFFFFFFF', mac_address * 20])
    msg = '' 

    ## Split up the hex values and pack.
    for i in range(0, len(data), 2):
        msg = ''.join([msg, struct.pack('B', int(data[i: i + 2], 16))])

    ## ...and send it to the broadcast address using UDP
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
    s.sendto(msg, ('10.0.11.127', 9))
    s.close()

def sys_exit():
    sys.stdout.flush()
    sys.exit(1)

## check if hostname is provided
if len(sys.argv) != 2:
    print "Usage: %s <hostname>" % sys.argv[0]
    sys_exit()

for i in node_lst:
    # strip off everything from first "#" found
    i = i.split('#',1)[0]
    if not re.search(X, i):
	continue

    h = S.split(i,1)[0]             ## host name
    m = S.split(i,1)[-1]            ## MAC address
    mmap[h] = m.strip('\t|" "')


for j, k in mmap.iteritems():
    if sys.argv[1] == j:
	if not re.search(X.replace('zA-Z','fA-F'), k):
	    print "Invalid MAC address [",k,"]; nothing to do!!"
	    sys_exit()
	else:
	    WakeOnLan(k.translate(f1_arg,':.-'))
	    print "WOL request has been sent to %s [%s]" % (j,k)
	    break
else:
    print "Host [%s] doesn't exist!!" % sys.argv[1]
    sys_exit()

Replace the sample MAC address[es] with the original ones. The "hostname" part doesn't have to be the actual host-name though and could be any thing - it's just to substitute the hard-to-remember MAC address with something easier to write whilst running the script. Don't forget to change the file-mode to 755

sudo chmod 755 /usr/local/bin/wake-on-lan

Run the script like this: wake-on-lan <hostname>; and the output should be something like this:

[admin@b_server WOL]$ wake-on-lan htpc
WOL request has been sent to htpc [00:24:7c:a2:e4:d0]

If everything goes well as describe above, you should be seeing the machine in the other room is booting up.