Change the behaviour of Alt Control Backspace to shutdown machine

Hi I am seting up a web kiosk, that uses a kiosk user to start a cut down web browser. The only shortcut keys that work are the Control + Alt + Back space which logs the user out and brings back the machine to a log in screen. Actually what I would like is for the machine to shut down instead of going back to the log in screen.
Any ideas?

The kiosk is started by automatically logging in the kiosk user, and having a xsession script in their home folder that starts firefox...

while true ; do
   /firefox/firefox -fullscreen

I dont fully understand what it is doing but it works!! Seems to start a System default session (its not gnome so i guess it may be twm), and when i hit alt contol back space it finishes that session and go's back to the log in screen. I would rather that users didnt get that screen and it would just shutdown.
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In X's config file  ( usually /etc/X11/XF86Config, /etc/X11/XF86Config-4 or /etc/X11/xorg.conf ).

Look for a section named ServerLayout, ie mine reads:

Section "ServerLayout"
        Identifier     "XFree86 Configured"
        Screen      0  "Screen0" 0 0
        InputDevice    "Mouse1" "CorePointer"
        InputDevice    "Keyboard0" "CoreKeyboard"

To this, add the line:
        Option "DontZap" "true"

(anywhere between the Section and EndSection lines.)

This will prevent X from dying on ctrl+alt+backspace .. I'm not however sure how to handle the next step, of having a client catch ctrl+alt+backspace and call a shutdown from it.

My advice, would be to enable DontZap so they're not returned to the login screen, then handle shutdown requests from /etc/inittab:

# What to do when CTRL-ALT-DEL is pressed.
ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now

.. appears to be the default.  Replacing -r with -h  will cause it to shutdown (to halt) rather than reboot.


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