This question already has an answer here:

I know that since 11.04 the keyboard short-cut of Ctrl+Alt+Backspace has been disabled by default. However at least as recently as 12.04 you were able to enable it via the Keyboard GUI:

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The Keyboard options in 14.04 are much more limited and there appears to be no way to re-enable this function:

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Is there any way to re-enable this function? All my searches of AU as well as a full internet search have provided no workable answers for 14.04.

merged by fossfreedom May 11 '14 at 21:58

This question was merged with How can I enable Ctrl+Alt+Backspace? because it is an exact duplicate of that question.