Sometimes programs tell me I can't start it because there is already another instance of it running. Best example would be Firefox and Chromium, but this problem accounts for many applications.

I cannot find the applications PID in the running processes.

How to kill all running instances of a program, e.g. Firefox?

I tried:

ps ax | grep firefox

But everything I can find is:

8193 ?        Rl     0:08 /usr/lib/firefox/firefox

I tried:

kill 8193

But I get:

Process not found

Actually, even when Firefox is running accurately, I cannot find its instances in ps.

What did I miss?

  • 3
    With killall firefox you will kill it. Commented Jan 10, 2013 at 19:47
  • 1
    and add a -9 if that doesn't work Commented Jan 11, 2013 at 12:41
  • This really hasn't been asked before?
    – Nobody
    Commented Oct 2, 2016 at 13:23

4 Answers 4


The easiest solution for a program that is not responding would be:

killall firefox

and if this doesn't work

killall -9 firefox

and if this still doesn't work, reboot, nothing else will.

For other killall options, see this article on Wikipedia: Link


Check if this works

kill -9 `ps -e | grep firefox | cut -b1-6`
  • So ps -e | grep firefox shows me the right process, interesting!
    – mcbetz
    Commented Jan 10, 2013 at 19:51
  • 2
    actually, pidof is much easier than this. pidof firefox will get you the right proces immediately. So the the solution could be kill -9 $(pidof firefox). ( the use of backticks (`) is depracated). But I prefer Uri Herrera's solution killall -9 firefox which should do exactly the same. Commented Jan 11, 2013 at 12:45
  • sudo kill -9 `ps -e | grep teamviewer | cut -b1-6` worked pidof did not (Ubuntu 16.04)
    – WiredIn
    Commented Nov 1, 2016 at 22:20

Also, to add more functionality to your Ubuntu system
go into settings > keyboard > keyboard shortcuts click add to add to a new shortcut
call the command forcequit or something
the command is xkill
set the shortcut to your choice of buttons
your mouse should turn into a 'x' and it will kill any process you click on


In certain circumstances kill and killall may not have the desired effect. This can happen, for instance, if the graphical container of a programme goes haywire. In such cases the process must be killed through xkill.

Simply open the a command line and run xkill. The mouse pointer becomes a cross and the following message appears:

Select the window whose client you wish to kill with button 1....

Then left-click with the mouse pointer on the window containing the rogue programme.

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