Unfortunately, of all the computers I own, the intersection of machines that are low power and machines that are capable of supporting a SATA HDD is the null set. This project aims to make a mode for Linux that leaves the system in a state that's useful as a server, but consuming minimal power.

Things that must be kept on

• Network
• SATA
• ACPI

Things that can be turned off

• USB
• Graphics card
• CPU to low frequency

Moving between modes

Sleepwalk mode might be a custom-defined ACPI power level (I'm not sure this is possible), or it could be a custom runlevel. Since USB should be off in sleepwalk mode, you can't switch out of sleepwalk mode with a USB keyboard. The reasonable way would be using the power button.

Relying on the kernel

I wonder if it's possible to just go to a console runlevel, and let the kernel manage suspending everything.