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Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.

I keep getting this error message when I try to shut down Firefox. It does not appear to be running on my desktop but my guess is that it is being used by another program in the background (to send an Error report, perhaps). How can I force Firefox to completely close?

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up vote 4 down vote accepted

To force completely close Firefox use:

pkill firefox

from terminal.

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Thanks. I guess my real question is why Firefox is staying open even though it looks like I closed it but this will work for now – Peter Schriver Nov 8 '12 at 17:41

In a terminal execute:

$ killall firefox

or, in some old versions,

$ killall mozilla (... and press the tab key to complete)

That will kill firefox. If the problem appears again, do the same, but if the problem happens almost always then you must have a deeper problem.

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