Ask Ubuntu is a question and answer site for Ubuntu users and developers. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

In Emacs run in terminal, ctrl+space is a standard shortcut key to select region. But under Ubuntu 12.04, it will invoke some input method for non-English language. I was wondering if I can reserve it for Emacs only?

Under System Settings -> Keyboard -> Shortcuts, I couldn't find to what ctrl+space has been bound. Strange.

Other programs, especially auto-complete in Eclipse, also seem to have a problem handling ctrl+space.

share|improve this question
Since you have some responses below that seem to answer your question, please consider marking one of them as ‘Accepted’ by clicking on the tickmark below their vote count (see How do you accept an answer?). This shows which answer helped you most, and it assigns reputation points to the author of the answer (and to you!). It's part of this site's idea to identify good questions and answers through upvotes and acceptance of answers. – Martin Schröder Jun 30 '15 at 7:31

It sounds like you have Ibus running, which uses Ctrl + Space by default to enable/disable the input editor.

You can change the shortcut key assigned to it in Ibus Preferences.

enter image description here

If Ibus is running in the menubar, you can right-click to choose Preference from the menu. If Ibus is not running in the menubar, you can start the Preferences dialog from the Dash by running Keyboard Input Methods or from the terminal with ibus-setup.

Update for 14.04

ibus-setup is no longer available for 14.04. Functions from the former ibus-setup are instead integrated into System Settings >> Text Entry.

Input switching is now set by default to Super + Space, but Ibus may still steal focus from the Control + Space keybinding and cause other system problems, most notably the auto-complete in Eclipse.

Integration of Ibus input switching into the new Text Entry settings is still a work in progress, and this is causing the problem since the older setting still exists behind the scenes.

If you have upgraded from 12.04, ibus-settings should still be available.

In 14.04, you can edit the settings directly is dconf-editor.

If it is not installed:

sudo apt install dconf-editor

Then browse to Desktop >> ibus >> general >> hotkey. The trigger and triggers setting will still show 'control+space'. Edit these settings out, being careful to leave empty brackets [] in triggers.

share|improve this answer
This also fixed autocomplete not working in Eclipse after I upgraded to xubuntu 14.04 – Brian Laframboise May 6 '14 at 13:50
My ibus-setup on 14.04 is slightly different and does not have that option. – BoppreH May 6 '14 at 17:50
@BoppreH 14.04 has changed ibus setup a little. I'll look into it. Thanks. – chaskes May 6 '14 at 17:51
dconf-editor fixed my problem, thank you very much @chaskes . – BoppreH May 6 '14 at 19:03
@BoppreH Glad it worked out. Please upvote (if you haven't done so). ;) – chaskes May 6 '14 at 19:04

Disable the IBUS trigger using the commandline:

gsettings set org.freedesktop.ibus.general.hotkey triggers @as []

Or if this does not work try if the first one produces an error:

gsettings set org.freedesktop.ibus.general.hotkey triggers []
share|improve this answer
The second command worked for me on a corporate customized version of Ubuntu 14.04 (goobuntu), which fixed my emacs problem copy/yank or copy/paste. – rrenaud Jul 7 '15 at 22:33
The second command fixed this for me, and it is now in my install script for setting up newly installed ubuntu desktops. Thanks, askubuntu! – Mnebuerquo Feb 1 at 1:02

After upgrade to ubuntu 14.04, I had the same problem. What I did.
In Ibus preferences: System > Preferences > Keyboard Input Methods.
There is an option: Next input method it was set to ctrl+space, I removed that and then all started to work back again.

share|improve this answer

ibus causes me nothing but headaches. Everytime that I try to change the settings, when I reboot, the Ctrl+Space comes back. Here's my solution:

sudo apt-get purge ibus
sudo killall ibus

Now everything works until Ubuntu decides their next stupid thing. Maybe the letter 'o' will map to turning off the computer?

share|improve this answer
I just tried this (Ubuntu 14.04.3 LTS). It didn't help. – Keith Thompson Dec 16 '15 at 20:26
CORRECTION: Either this, or changing the IBus preferences, or running dconf-editor, did work. I was testing by typing Ctrl-V Ctrl-Space in bash; for some reason bash wasn't accepting it. But Ctrl-Space is generating a null character. – Keith Thompson Dec 16 '15 at 20:46

Ubuntu Studio 14.04 (XFCE) here. I didn't have problem with Autocomplete (Ctrl + Space), but with Copy Line (Ctrl + Alt + Down).

This worked for me:

  • Open Windows Manager: xfwm4-settings
  • Go to Keyboard tab
  • Scroll down to conflicting Action
  • Hit Clear button or change action to different shortcut
share|improve this answer
Thanks! This can be done on command line, too xfconf-query -c xfce4-keyboard-shortcuts -r -p " /xfwm4/custom/<Primary><Alt>Up" ; xfconf-query -c xfce4-keyboard-shortcuts -r -p " /xfwm4/custom/<Primary><Alt>Down" ; xfconf-query -c xfce4-keyboard-shortcuts -r -p " /xfwm4/custom/<Primary><Alt>Left" ; xfconf-query -c xfce4-keyboard-shortcuts -r -p " /xfwm4/custom/<Primary><Alt>Right" . – Stéphane Gourichon Jun 2 at 10:20

I have Ubuntu 14.04 GNOME with LXDE. Apparently this desktop has ibus-setup. So, for me, changing the ibus setting was the right fix. Perhaps it was only Unity that did away with the ibus-setup app.

share|improve this answer
Yes, it's a Unity thing. – Gunnar Hjalmarsson Dec 28 '14 at 5:02

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.