Firefox already running on Ubuntu Linux

Problem

I recently worked on a Ubuntu linux machine that would not let me open mozilla. the error message was "Firefox already running..please shut down...blah blah.."
I had only just logged into the machine - it was obviously confused.

Solution

$ cd ~
$ cd .mozilla
$ ls
listing of files; look for "something.default"
$ cd something.default
$ ls -a
listing of files; look for .parentlock
$ rm .parentlock

I tried starting firefox again, and it was happy.

Acknowledgements

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