I recently began using my laptop at my desk with a USB keyboard and mouse, and I thought I would explain how to set up Ubuntu so that USB peripherals will wake up your computer from sleep mode. This is convenient if you have your laptop set up such that the lid is closed and inaccessible.

In Ubuntu, the way to set this up is to edit the file located at /proc/acpi/wakeup. To see the current contents of this file do this:

% cat /proc/acpi/wakeup
Device	S-state	  Status   Sysfs node
P0P2	  S4	 disabled  
P0P1	  S4	 disabled  pci:0000:00:1e.0
MC97	  S4	 disabled  
HDAC	  S4	 disabled  pci:0000:00:1b.0
P0P4	  S4	 disabled  pci:0000:00:1c.0
P0P5	  S4	 disabled  pci:0000:00:1c.1
P0P7	  S4	 disabled  
P0P8	  S4	 disabled  
P0P9	  S4	 disabled  
USB0	  S3	 disabled  pci:0000:00:1d.0
USB1	  S3	 disabled  pci:0000:00:1d.1
USB2	  S3	 disabled  pci:0000:00:1d.2
USB3	  S3	 disabled  pci:0000:00:1d.3
EUSB	  S3	 disabled  pci:0000:00:1d.7
P0P6	  S4	 disabled  pci:0000:00:1c.2
SLPB	  S4	*enabled

Once these are toggled on, your computer will wake up from sleep when USB peripherals are used. To toggle one of these on, as root, run:

echo "USB0" > /proc/acpi/wakeup

This will set up your computer to wake up from USB...for now. To make it work after your computer has been restarted, you will need to write a short init script named wake.sh with the following contents:

#!/bin/bash
echo "USB0" > /proc/acpi/wakeup

Source: http://ubuntuforums.org/showthread.php?t=711747