Firefox ‘already running’ bug -> delete .parentlock file
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)
This bug also appears in MS Windows, as I searched on internet.
The file to be deleted there is
“C:\Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles\<session>.default\parent.lock” on Windows Vista,
“C:\Document and Settings\<username>\Application Data\Mozilla\Firefox\Profiles\<session>.default\parent.lock” on Windows XP/2000,
and finally
“C:\WINDOWS\Application Data\Mozilla\Firefox\Profiles\<session>.default\parent.lock” on Windows 98/Me.
Same problem exists on Sun Solaris lol… It’s getting quite old to delete the .parentlock file everyday…
Thanks!! The same problem also turned up on my Ubuntu machine today after I had to forced restart the entire machine. Your solution solved it!