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