Note: This post documents a change that was introduced in Fedora 11 (F11). Special thanks to who-t for his help on this one 
Previously, pressing the key combination Ctrl+Alt+Backspace forced the X.org server (the open source implementation of X11) to instantly restart, returning the user to the login screen. This functionality is useful on unstable systems where the X server frequently hangs, however, if the shortcut is inadvertently invoked, the user will lose anything not saved to disk. In the version of X.org shipped in Fedora 11, the decision was made in upstream to make the Ctrl+Alt+Backspace shortcut disabled by default. To re-enable this option (on the Gnome Desktop):
1. Open the Keyboard Preferences dialog either by choosing System > Preferences > Keyboard from the Fedora Main Menu or by running the following command from a terminal:
gnome-keyboard-properties
2. In the Keyboard Preferences dialog, choose the Layouts tab (labeled 1 in the screenshot below) and press the Layout Options button (labeled 2 in the screenshot below) to bring up the Keyboard Layout Options dialog.
Keyboard Preferences dialog
3. In the Keyboard Layout Options dialog, unfold the tree item “Key sequence to kill the X server” (labeled 3 in the screenshot below), and mark the checkbox “Control + Alt + Backspace” (labeled 4 in the screenshot below)
Keyboard Layout Options dialog
Update: X input hacker, who-t (Peter Hutterer) on the differences between Ubuntu and Fedora on this change:
The Ubuntu “dontzap” command has no effect on Fedora.
There are two parts to zapping: one is the permission in the server (Option DontZap) and one is the trigger (the Terminate_Server XKB symbol). To zap, you have to invoke the trigger and you must be allowed to zap the server.
In Ubuntu, the server by default does not allow zapping, but the trigger is in the default keymaps. Thus, to enable zapping it needs to be enabled in the configuration file (and the server requires a restart).
In Fedora, the server by default allows zapping, but the trigger is not in the default keymaps. Thus, to enable zapping it needs to be enabled in the keymap. This can be done at runtime.
Doing the equivalent to “dontzap -disable” in Fedora explicitly enables an option that’s enabled by default anyway, so it has no effect.
June 10, 2009 at 11:31 pm |
I ran into this last night, it kinda surprised me that it didn’t work. Thanks for the heads up on how to reenable it.
June 11, 2009 at 3:46 am |
I don’t have F11, but ubuntu jaunty recently implemented the same thing. You can disable this by running `dontzap –disable` into the terminal. It’s most likely the same, but maybe not as I haven’t tried.
June 11, 2009 at 5:35 am |
@jay: NP, thanks for leaving a nice comment too
@JoshWIlliams: it sounds like the same change to X, but with different ways to re-enable it. Did you have to run “dontzap –disable” as sudo? In the F11 release notes, it says to add a “DontZap” line to xorg.conf, but this requires root (sudo) access, and re-enables the shortcut system-wide, while using the “Keyboard Preferences” turns it on for a single user.
June 15, 2009 at 10:49 am |
For clarification on ubuntu (and probably debian testing) you will need to fetch dontzap. Run:
sudo apt-get install dontzap
then run (as root):
sudo dontzap –disable
I believe this will be a system wide setting which is fine for me. I’ve never had anyone using my computer ever restart the x server by accident.
June 15, 2009 at 10:51 am
Edit: that’s actually supposed to read
sudo dontzap –disable
(with two hyphens)
June 11, 2009 at 9:14 am |
The Ubuntu “dontzap” command has no effect on Fedora.
There are two parts to zapping: one is the permission in the server (Option DontZap) and one is the trigger (the Terminate_Server XKB symbol). To zap, you have to invoke the trigger and you must be allowed to zap the server.
In Ubuntu, the server by default does not allow zapping, but the trigger is in the default keymaps. Thus, to enable zapping it needs to be enabled in the configuration file (and the server requires a restart).
In Fedora, the server by default allows zapping, but the trigger is not in the default keymaps. Thus, to enable zapping it needs to be enabled in the keymap. This can be done at runtime.
Doing the equivalent to “dontzap -disable” in Fedora explicitly enables an option that’s enabled by default anyway, so it has no effect.
June 12, 2009 at 1:25 pm |
I have done what you’ve recommended as well as editing the xorg.conf file….and each method works….kinda:
It does not actually let me simply disable the xserver, it just logs me out and forces me to log back into the GUI. Am I missing something? I’d like to really give Fedora 11 a full try but this frustration is driving me back to Ubuntu on the desktop. Thanks for your help and post!
June 15, 2009 at 5:47 pm |
Jason, if you want to be able to disable the xserver, you can change your default run level. This is done by editing /etc/inittab. There is a line which reads “id:5:initdefault:”
If you edit this file, and change the 5(X11) to 3(full multiuser mode), your computer will boot into text mode to start with. To start X, log in and run “startx”.
With this setup, and enabled ctl-alt-backspace you can flash back into text mode if you need to.
June 13, 2009 at 5:07 am |
Jason Ashton the ctrl-alt-bksp trigger has never disabled the x server only restarted it, so i don’t see why you think it will disable it? or that any of the options to re-enable the zapping will help disable the x server. if you want to run without the x server start in runlevel 3 or log in with x started then as root init 3
June 17, 2009 at 4:06 am |
Thank You!
June 28, 2009 at 4:24 pm |
Re: booting into text mode – guys using ubuntu will be astonished to find that the runlevel method does not work. Ubuntu has an amazingly convoluted way to boot into text mode.
Without question Fedora is far more sensible in this particular regard, although IMHO disabled control-alt-backspace by default is a BRAIN DEAD decision by the upstream guys.
September 8, 2009 at 7:46 am |
Agree with Fred – the decision upstream to disable control-alt-backspace by default was UNBELIEVABLY STUPID. In the history of the world, nobody EVER hit this key combination by mistake. It’s an IDIOTIC thing to worry about. The day X reaches perfection and never locks up is not on the horizon, and probably will not occur during the liftetime of anyone presently living.
Agree also with Fred that Ubuntu (probably Debian actually) makes it INSANELY difficult to switch between text mode operation and X operation. This ALONE is basically the deal breaker that prevents me switching.
phil is _partially_ right. He’s right that control-alt-backspace never disabled X, but he’s wrong that it restarts X. It KILLS X. It is the display manager that restarts X in the form of the login greeter whenever it detects that X has died.
September 19, 2009 at 11:32 am |
Thanks brother.. i am a kde user and found a similar procedure there.
go to “system settings >> regional & language >> keyboard layout >>”
enable keyboard layouts, then u can find the “Key sequence to kill the X server” under Advanced tab.
October 21, 2009 at 7:25 am |
And last but not least for the Xfce and LXDE users: run
in your autostart.
November 26, 2009 at 11:34 am |
Useful.. thanks a lot.