I’m using a Debian amd64 install with the default GNOME desktop. I’m aware that you can go into System | Preferences | Power Management, and choose to make the display go to sleep after a certain period of inactivity. However, I currently have that set to ‘Never’ because until I lock the screen, I don’t want the display to go to sleep. Once I lock the screen, though, I want it to go to sleep immediately unless/until it detects activity, or at least go to sleep after 1 minute or something. Is there a way I can configure it to do this only when I ‘Lock Screen’?
You could run a script:
#!/bin/bash gnome-screensaver-command --lock xset dpms force off
Bind this to a key sequence and whenever you lock your screen, the display will turn off.