How to activate CTRL-ALT-BACKSPACE

[hugocoolens]

What I miss on my rpi with xbian is response to ctrl-alt-backspace.
I tried to use dpkg-reconfigure keyboard-configuration but unfortunately
the usual option which lets you configure ctrl-alt-backspace is not presented. Does someone here now how to do it?
The reason I want it is for those times I did not take note of the ip-address and the rpi hangs, the only thing I can do then is remove the power but this can lead to file system corruption, ctrl-alt-back space could give me the choice to properly halt the system without damage.

thanks in advance
hugo