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HOW-TO:Set up Wake-On-Lan (Ubuntu)

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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 (WOL) is a network standard, which provides the ability to switch on remote computers through special network packets, called Magic Packet from sleeping, hibernating, or powered-off state. It only works with Wake-On-LAN compliant BIOS and NIC.

Contents

1 Before we start

First of all, the motherboard should support Wake-On-LAN and it should be enabled in the BIOS.

Different BIOSs and motherboards do this differently; for example on the ASUS P5N7A-VM, it's under Power > APM Configuration and in there Resume On PCIE Wake and Resume On LAN(MAC) should be enabled.

2 Enabling WOL in the OS

Even though Wake-On-LAN works in network layer 2, OS support is still one of the important things to make it work. Even if you see the Ethernet port LED 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.

2.1 Install ethtool

One of the easiest applications to use to enable Wake-On-LAN is ethtool. Install it with:

sudo apt-get install ethtool

2.2 Setup ethtool WOL options

Run the following command to enable it on ethX (where X is the Ethernet device number).

sudo ethtool -s eth0 wol g
  • Note: Not all devices support this.

The settings can be verified by running:

sudo ethtool eth0
 Settings for eth0:
 	Supported ports: [ MII ]
 	Supported link modes:   10baseT/Half 10baseT/Full 
 	...
         ...
 	Supports Wake-on: g
 	Wake-on: g
 	Link detected: yes
  • Note: "g" indicates wake on Magic Packet is enabled

2.3 Enable ethtool on Start-up

To have an application or service is running on startup, Ubuntu uses Upstart scripts which replace the old init scripts.

The following commands; create wakeonlan.conf with the upstart code to run wakeonlan (as per example above), set the file to exectuable, and start the service[1]:

sudo bash -c "cat > /etc/init/wakeonlan.conf" <<'EOF'
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
EOF

sudo chmod +x /etc/init/wakeonlan.conf

sudo service wakeonlan start

3 Waking with Magic Packet

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 the OS it boots into afterwards.

The following steps are for setting up a Wake-on-LAN application on Ubuntu but there are many applications available, including for Windows and Mac OS X, that accomplish the same task.

Install our Wake-on-LAN application, in this case powerwake, as it has IP and hostname options.

sudo apt-get install powerwake

The simplest usage of powerwake is to just supply the IP address or hostname of the machine you want to wake:

powerwake 192.168.1.1

powerwake xbmc-hostname.local
  • Note: To enable powerwake to cache the remote machine MAC address you may need to run it once with the remote machine awake.

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

4 Finishing Touches

4.1 Aliases

You can make it even easier to run the above application from the command line or other scripts. One way is to include aliases to it in your .bashrc file, found in your user's home directory. Open the file in your preferred text editor and scroll to the bottom of the file, then add one or more of the lines below, depending on what you need to do.

nano ~/.bashrc

# User Defined Aliases
alias htpcwol="powerwake xbmc-hostname.local"
alias htpcssh="powerwake xbmc-hostname.local; ssh user@xbmc-hostname.local"

Save and exit, then run the following to reload it (normally loaded automatically at startup):

source ~/.bashrc

You will now have two new commands (aliases) available for use from the command line; the first alias htpcwol simple wakes the host up remotely and the second one htpcssh also wakes it up but then creates an SSH session to the remote machine.

Aliases are a huge time saver if you use the command line for remote access often and there are many examples on the internet.[2]

4.2 Suspend or Hibernate from command line

To suspend the remote machine from within an SSH session set the suspend command to run several minutes in the future:[3]

echo 'pm-suspend' | sudo at now + 3 minutes

You can then disconnect safely from the SSH session and the remote machine will suspend at the set time.

4.3 Using the XBMC Remote Control

It took me some time to figure out why my XBMC did not wake up from shutdown. Commands to shutdown systems often work best when issuing them against MAC addresses. If you are using the XBMC Remote Control app on the iPad or iPhone, you must supply the MAC address (or: HWaddr) of your NIC in the setup. I can now shutdown and startup XBMC from the app.

To find out the HWaddr on XBMCbuntu use this command:

ifconfig | grep HWaddr

5 References

  1. http://askubuntu.com/questions/47918/how-can-i-enable-wake-on-lan-permanently
  2. http://www.howtogeek.com/73768/how-to-use-aliases-to-customize-ubuntu-commands/
  3. http://askubuntu.com/questions/35719/how-do-i-suspend-over-ssh
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