In 12.04 How do you kill the X server from the command line and from the GUI interface and how do you start it from the virtual terminal?


4 Answers 4


One way to restart an instance of the X server is to run (from the commandline)

sudo service lightdm restart

For Ubuntu 15.04 and later:

sudo systemctl restart lightdm.service

and for Kubuntu 15.04 and later:

sudo systemctl stop sddm.service
  • 1
    lightdm? I thought gdm was for GNOME, kdm for KDE, xdm for XFCE and lightdm for LXDE! and to stp it from the gUI?
    – Robert
    May 3, 2012 at 22:26
  • 2
    lightdm is the default for 12.04, I'm not sure when it was made the default perhaps in 11.10?
    – labarna
    May 3, 2012 at 23:50
  • 1
    restarting lightdm doesn't kill Xorg. Only an instance of it. May 5, 2013 at 0:23
  • 2
    lightdm starts only one instance of Xorg, so restarting lightdm should close the only open Xorg instance, unless you're doing something much more complicated.
    – labarna
    May 6, 2013 at 13:05

On 12.04, you can restart the server with the shortcut keys: Right Alt + Print Screen + K.

  • 1
    What a strange combination!. Print??. It has no logic; and what would "(Right alt) + (Print Screen) + K" be in an Apple keyboard? I have right command and no print
    – Robert
    May 3, 2012 at 22:30
  • 1
    en.wikipedia.org/wiki/Magic_SysRq_key has more info on it if you want to understand the logic behind it. printscreen is the same key as sysrq(System Request).
    – semi
    Jul 11, 2012 at 23:43
  • @semi: "printscreen is the same key as sysrq" - not on my keyboard. sysreq is the same key as delete. May 4, 2013 at 23:28
  • 4
    Nothing happens on my machine (fresh install of 13.10). Nov 14, 2013 at 1:11
  • 1
    In order for this to work you need to run this command once: sudo echo kernel.sysrq=1 > /etc/sysctl.d/10-magic-sysrq.conf
    – Naveen
    May 30, 2015 at 11:39

In Ubuntu 14.04:

Press Ctrl+Alt+F1 and then run:

sudo service gdm stop


sudo service lightdm stop

… depending on your display manager.

NOTE: To recover use startx, alternatively replace the stop with start in either of the above commands.


Kill : xkill -a. -a means it will kill all display instances. For more information run man xkill.

Run : xinit. Also startx but this command is to start an instance and not the server itself. For more information run man xint and man startx.

I don't believe it's possible to kill Xserver from GUI, and even if it were, it would not be the right way to do it.

  • Wouldn't that kill all individual windows, which is not what the user wants? For example I don't want to kill all my firefox windows, I want to restart the visualisation. Aug 23, 2013 at 1:47
  • 4
    The user said: "kill and start the X server". That seems to be exactly what he wants. It's not about restarting gnome-shell.
    – Gui Ambros
    Jun 26, 2014 at 1:16
  • Doesn't work for me from tty: Unable to open display ""
    – xeruf
    Mar 1, 2021 at 10:43
  • This is more generalized than restarting lightdm services in case you don't have a display manager. UPVOTE! Mar 17, 2021 at 22:58

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