This is a function of the BIOS. There's a couple different power management standards, and Linux has some utilities that let you use these BIOS functions:
If you have ACPI,
this thread suggests:
Code:
echo 4 > /proc/acpi/sleep
If, like me, you don't have that, and you have APM, you can do:
The lowercase -s is "suspend" mode, the uppercase -S is "standby" mode. Standby mode doesn't work for me but suspend does (although, I have to press the power button to wake it up, it doesn't respond to keyboard/mouse events). Check out the apm man page for more info.
Hope that helps,
Jason