12.14. Power Key

The power key often has different functions, besides power on and off it may be used to wake up the machine from suspend mode. This is usually achieved by pressing the power button for just a few seconds only. If you press it longer (app. more than 5 seconds) it will power down fully.

With modern laptops supporting ACPI it's also possible to achieve power off, with ACPI via the /proc/apci/ interface.