Frequently Asked Questions
UBC Mathematics: MathNet FAQ [Browser Busy]

UBC Mathematics: MathNet FAQ [Browser Busy]

Question: How do I handle complaints from Firefox that another browser is running?
Author: Joseph Tam
Date: Dec. 07, 2010

Quick Fix

This usually only happens on the Unix (Solaris, Linux, etc.) version of Firefox. For a quick and fast fix, run this command on the same workstation you usually run Firefox on:

For a more detailed explanation and details on what the script is doing, please read the next section.

Technical Details

A browser will refuse to start if it believes another instance of itself is running elsewhere. It does this to ensure the consistency of its data (bookmarks, browsing history, etc.) by making sure another browser is not abot to modify it at the same time.

A browser checks the existence of a lock file created by another browser. Problems arise if the original browser that created the lock file crashes or ends abnormally without removing its lock file, thus preventing new browser instances from starting up.

Firefox's lock files are typically located in one of several locations:


The lock file may give an indication which browser owns the lock

	> cd ~/.mozilla/firefox/38cnrd87.profile
	> ls -l lock
	lrwxrwxrwx 1 smith wesson  18 Jan 12 15:54 lock ->

In the example, the lock is owned by a browser running at host address with process id 9876.

The first step to unlocking the browser is to check whether another browser is really holding a lock. It may be running on another terminal or on another workstation; closing that application will release the lock.

	> ssh smith@
	> ps -p 9876

If this process exists (and you're not in a position to manually close the application), you can kill the process by using the command

	> kill 9876

	# ... or in extreme cases ...
	> kill -9 9876

Once you're sure browser is gone, you can remove the lock file if it exists:

	> rm ~/.mozilla/firefox/38cnrd87.profile/lock

If you still can't get a browser to start, contact the IT staff.