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.


8 Answers 8


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.

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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.

  • 3
    This also fixed autocomplete not working in Eclipse after I upgraded to xubuntu 14.04 May 6, 2014 at 13:50
  • My ibus-setup on 14.04 is slightly different and does not have that option.
    – BoppreH
    May 6, 2014 at 17:50
  • @BoppreH 14.04 has changed ibus setup a little. I'll look into it. Thanks.
    – chaskes
    May 6, 2014 at 17:51
  • 4
    dconf-editor fixed my problem, thank you very much @chaskes .
    – BoppreH
    May 6, 2014 at 19:03
  • 2
    @BoppreH Glad it worked out. Please upvote (if you haven't done so). ;)
    – chaskes
    May 6, 2014 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 []
  • 2
    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, 2015 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, 2016 at 1:02

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?

  • I just tried this (Ubuntu 14.04.3 LTS). It didn't help. Dec 16, 2015 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. Dec 16, 2015 at 20:46

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.


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
  • 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" . Jun 2, 2016 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.


The dconf-editor change was not sufficient for me. I have the Mozc (Japanese) input source installed.

On Ubuntu 16.04, I also had to:

  1. Go to System Settings -> Text Entry
  2. Click Mozc to highlight
  3. Click the wrench/screwdriver icon below
  4. Global Config tab
  5. The first setting there, "Trigger Input Method," was CTRL_SPACE. I clicked it and then hit Escape to unset the keybinding.

For some people using Japanese input with fcitx, check Fcitx Configuration. There's a menu for global configuration, and under Trigger Input Method, the default shortcut will be Ctrl + Space.

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