Firefox ‘already running’ bug -> delete .parentlock file

February 11, 2009 by V-Teq · 3 Comments
Filed under: CentOS 


I came across a strange bug today, using CentOS Linux. The whole system suddenly froze up and I had to restart the whole computer (it was not even possible to change to any TTY using CTRL+ALT+F[0-8] or restart X by pushing CTRL+ALT+BACKSPACE). But after rebooting I couldn’t start Mozilla Firefox browser.

Error dialogue during a Firefox startup:

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.

The solution is to delete .parentlock file in your firefox home directory.

$ rm ~/.mozilla/firefox/<session>.default/.parentlock
# substitute <session> with your default session (or '*' should probably work too)

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