Firefox won't open - dialog says already open

[FredVanH]

Hi. I tried to invoke Firefox in Ubuntu 10.04. I got a dialog box entitled “Close Firefox”, which said:
“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 had not recently had Firefox running; so there was no instance of Firefox showing on the desktop display.


I have had this problem from time to time in the past; but just rebooted. Seems like there should be a better way. Any ideas as to:
1. How that unknown instance of Firefox got orphaned?, and
2. How to fix the problem without rebooting?
Thanks,
Fred

[Quackers]

You could try opening system monitor and under the processes tab see if there is an entry for firefox.bin running. If there is highlight it and click on "end process".
It may not appear at all in system monitor though.

[altometer]

CTRL+ALT+T type TOP and hit enter
If you see a process called "Firefox" press K and type the number in the process ID column. Then press enter.

[ajgreeny]

You can also try

killall firefox

in terminal or just reboot, but try to kill it first if you can, to save rebooting, which should not be necessary.

[FredVanH]

Thanks, Quackers & Altometer for your kind and timely responses.

Quackers, I tried yours first and the firefox binary was indeed listed in System Monitor.
It looked like all I had to do was highlight its entry and push the "End Process" button. I postponed doing it because I also wanted to see the other solution. Thanks!

Altometer, I then tried yours:
Ctrl-Alt-T got me into Terminal (nice - now I know 1 more thing),
"TOP" was rejected but "top" got me into the processes display and there indeed was the firefox binary listed on the first line.
Typing "K" brought up the Kill Process 1-line dialog.
I typed the Firefox binary's PDID number and hit Enter.
What looked like a failsafe message came up: "Kill PDID 3914 with signal [15]:"
I typed "Y" for Yes and hit enter. The display changed a little but Firefox was still there.
I typed "15" and hit enter. The display changed a little but Firefox was still there.
I merely hit enter. The display changed a little but Firefox was still there.
What did I miss?
Thanks,
Fred

[The Cog]

I haven't used system monitor to kill processes. I have sometimes seen tha tproblem where firefox-bin is running but has no visible window, making it impossible to launch a new firefox properly. I think this command has always worked for me:

killall firefox-bin

but if that doesn't do it, this should:

killall -9 firefox-bin

[Quackers]

It looks like it won't respond.
Try the system monitor method and see if it does the same.
The only other thing I would try is to shutdown fully and try a cold boot.
It would be interesting to know where the instruction to start the bogus firefox is coming from though.

[The Cog]

It would be interesting to know where the instruction to start the bogus firefox is coming from though.

I think it happens when a legitemate firefox fails to shut down properly - the window disappears but some part is left running. It seems to happen to me occasionally when firefox gets unresponsive on certain page contents and I close it with the intention of starting a new one. I haven't seen it happen so much recently though, so I guess FF is getting better.