On Thu, 19 May 2016 14:19:50 +0200, Emninger wrote:
> [ . . . ]
>
>>> 2) Terminate X via Ctrl-Alt-Backspace

<snip>

> For me that's useful, especially since often the logout tools do not
> work like expected (in my limited experience).
>
> I notice, that key combination does not work by default in Devuan, so my
> question: Where and how can it be activated?

<snip>

Put the following in e.g. your ~/.xsessionrc :

setxkbmap -option terminate:ctrl_alt_bksp

HTH
Urban