How to force any program to close?

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?

Solution 1:

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

Solution 2:

Check if this works

kill -9 `ps -e | grep firefox | cut -b1-6`

Solution 3:

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