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If you want to put your machine into hibernation, and also require a password on coming back up, do this:

xscreensaver-command -lock && hibernate

You need the xscreensaver package installed.

And the hibernate command seemed to appear in 2012.

You may also want to put the lock command in a script, named 'lock', for easier typing:

#!/bin/bash
xscreensaver-command --lock