How to enable/disable Ctrl+Alt+Backspace in Ubuntu 9.10 (Karmic)

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Ctrl+Alt+Backspace (i.e. the shortcut which was used to restart the X server) has to be enabled in a different way with respect to previous releases of Ubuntu.

This is due to the fact that “DontZap” is no longer an option in the X server and has become an option in XKB instead.


* Get to the System->Preferences->Keyboard menu.

* Select the "Layouts" tab and click on the "Layout Options" button.

* Then select "Key sequence to kill the X server" and enable "Control + Alt + Backspace".

Using KDE

* Launch "systemsettings"

* Select "Regional & Language".

* Select "Keyboard Layout".

* Click on "Enable keyboard layouts" (in the Layout tab).

* Select the "Advanced" tab. Then select "Key sequence to kill the X server" and enable "Control + Alt + Backspace".

Using the command line

You can type the following command to enable Zapping immediately.

setxkbmap -option terminate:ctrl_alt_bksp

If you're happy with the new behaviour you can add that command to your ~/.xinitrc in order to make the change permanent.

Using HAL

You can add the following line in /usr/share/hal/fdi/policy/10osvendor/10-x11-input.fdi (inside the <match key="info.capabilities" contains="input.keys"> section):

<merge key="input.xkb.options" type="string">terminate:ctrl_alt_bksp</merge>

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15 Responses

  1. Danny says:

    The reason this was taken out was to use the traditional “Magic SysRq Keys” ( ), which operate at a kernel level instead of the xorg level. Now alt+SysRq+K does was ctrl+alt+backspace did. There are plenty of other SysRq keys that do lots of fancy things, so I suggest you check it out.

  2. Adrian says:

    Actually, the reason this was taken out was because some a**hole kept killing his X11 when using Emacs’s to delete the {}-enclosed structural block to the left of the cursor. I mean, come on! So let’s impact all users just because one application can’t change its key binding. My blood boils when I see this topic mentioned. 😛

  3. Steve says:

    My blood boils when I see people trying to negatively impact all other computer users just because they don’t personally mind when they accidentally kill everything with a common key combination.

    This key combination has always been a bad idea. Disable it and keep our computers user-friendly.

    Arrogant nerds like Adrian are smart enough to figure out how to re-enable it themselves if they refuse to learn the SysRq keys. I don’t understand why those people use Ubuntu in the first place.

  4. Keith says:

    I’ve created a Ubuntu Brainstorm suggestion to make it easier to find the option:

    Feel free to vote it up, or add other ideas 🙂

  5. Thank you very much for this article. /Me thinks removing the dont-zap function from Ubuntu is the dumbest decision ever made inside Ubuntu. After installing the dontzap package, all Ctrl, Alt and Backspace did was freezing the entire system.

    This is great and Keith’s suggestion is even better 😉

  6. piratebill says:


    Since when was ctrl+alt+backspace a common key combination? I cant think of a single reason a common user would use that combination.

  7. The reason I use ubuntu is because I want something that is easy *and* powerful, not *or*. 9.10 has seems to do lots of things in obscure ways. I mean, the hal fdi policy? Putting the option in the x config seems to have worked for 15 years … why is it broken now? Is this really progress or is it just moving stuff around?

  8. Nic Mansfield says:

    @ Steve —

    I’m sorry to hear that your blood was recently boiled.

    If you think that Ctrl+Alt+Backspace is a commonly used key-combo, you are insane. Unless you “commonly” restart your X, this key-combo is almost never used.

    Changing a well known / industry standard command to an incredibly awkward / difficult to remember key combination, for no apparent reason is totally stupid.

    I’m aware there’s a fix. The point is… making a change like this, that offers no improved functionality, is a waste of the developers time, as well as the users who have to relearn something that worked fine before it was changed.

    So, before you start acting “holier than thou” and spewing insults at us “arrogant nerds…” perhaps you should make sure you don’t sound like an ignorant fool.

  9. graeme says:

    Unfortunately moving the C-A-Bspace into USER config makes it available far too late .

    My KVM means the mouse does not work and the screen is the wrong resolution … I need to do C-A-Backspace to fix to BEFORE logging on.

  10. graeme says:

    To add insult … the alt-sysrec-K does NOT work

    On my redhat systems resrq is disabled by default (similar woolly thinking as to the C-A-backspace )

    On ONE my Ubuntu boxes it does work. The reason I’d not noticed is that on all the other boxes it does print-screen … as do all Alt-Sysreq combos … BTW same physical keyboard on both machines same physical keys hit.

    … so to be clear C-A-backspace has worked on all systems for past 20 years … it still works on most…Alt-Sysrq has not worked (by default) on any on my systems to date … and now ONLY works on one Ubuntu machine.

    I want C-A-backspace backe BEFORE logging on … or is there some windoze magic that affects users even before they log on?

  11. Foobar says:

    Great stuff.

    The X on my laptop which has an Intel GPU refuses to work without a few rapid restarts on Ubuntu distros.

    What’s the replacement key combo?

    /me curses X server – never worked, never will.

  12. graeme says:

    probably C-A-SysRq-K
    if that does not work make sure sysrq is not disabled:

    $ cat /proc/sys/kernel/sysrq

    (mine is OK)

    if it’s off you can set it back on as root:

    echo 1 > /proc/sys/kernel/sysrq

    but it’ll get reset on next boot … so see who turns it off
    try cat /etc/sysctl.conf as a start

    … all in all it’s rubbish

  13. alexander says:

    but it’ll get reset on next boot … so see who turns it off
    try cat /etc/sysctl.conf as a start

    … all in all it’s rubbish

  14. anonymous-knoppix-user says:

    the (ctrl+alt+)backspace is right below
    the (ctrl+alt+)f12 on my keyboard; so,
    it is very annoying to hit it accidentally
    while trying to view the error console
    (which of course is swamped during reset).

    would a confirm reset dialog be too much?

    for kiosks, a convenient way to disable
    it from the boot: prompt would also be nice.

  15. graeme says:

    Nope, having a pop-up window would also render it unusable. Quite a lot of time when you need to hit this sequence, the display is not visible. For example the refresh=h rate is wrong.

    You need a reliable, always present, key sequence which always clears down to a known (secure) input

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