Shutdown shortcut

• Start 'Keyboard':

gnome-control-center keyboard

• Go to the tab 'Shortcuts' and add a Custom Shortcut with '+'
• Pick a name, for example 'Shutdown'
• Configure the shutdown command (this command will ask confirmation first):

/usr/lib/indicator-session/gtk-logout-helper --shutdown

• Configure a key combination, for example 'Ctrl+Alt+Delete'