Linux Power Management Notifications

Question

What approach (the simplest) that we can use to receive notifications about changes in the power state (for example, when a computer goes into sleep mode, sleep mode, etc.) on Linux-based systems?

I need this mainly to save some state before going to bed and, of course, restore the state after the computer wakes up.

Answer 1

You can get all of these events by simply configuring acpid to send them over the socket, for example.

There is an official specification document that describes all possible events and circumstances. Extensive reading though.