A boot script run after the network cards are configured should do the trick. Ubuntu uses upstart. After reading about upstart jobs, ethtool, writing an upstart script, and searching the interwebs for a better solution, I came up with this from jevinskie (you'll want to put this in a file in /etc/init):

start on started network



script

    for interface in $(cut -d: -f1 /proc/net/dev | tail -n +3); do

        logger -t 'wakeonlan init script' enabling wake on lan for $interface

        ethtool -s $interface wol g

    done

end script

• Starts when the nics are initialised


• Grabs the nic names from /proc/net/dev


• Logs actions to syslog


• Acts on all nics found



• Requires ethtool, so make sure it's installed first:

  
  
  

  sudo apt-get install ethtool
  
  

If you want to imbue just one nic with the power of awakening, something like this is more appropriate:

start on started network



script

    interface=eth0

    logger -t 'wakeonlan init script' enabling wake on lan for $interface

    ethtool -s $interface wol g

end script