gsettings set org.gnome.settings-daemon.plugins.power button-power shutdown
will change your the behaviour of the power button of your system from interactive (default) to immediate normal shutdown.
The command is gsettings set org.gnome.settings-daemon.plugins.power button-power <option>
Available options are:
- Blank: does nothing
- Suspend: makes your system suspend
- Shutdown: starts a normal issued shutdown procedure
- Hibernate: hibernates your system
- Nothing: does nothing
- Log out: log your user out
参考链接：http://askubuntu.com/questions/430776/how-can-i-modify-the-power-button-behaviour