The "Mozilla is already in use" message - Curse of the parent.lock file




When the Mozilla program is launched, it creates a file called "parent.lock" in the profile directory. The presence of this file tells Mozilla that the program is already open on another computer, and that it shouldn't use the profile. 2 instances of Mozilla modifying the same profile files could lead to corruption.

If Mozilla sees the parent.lock file when it starts up, it will launch the Profile Manager automatically and ask you to create a new profile directory for it to use.

The icons that we use to launch Mozilla on CLASnet administered machines check for the presence of the parent.lock file before launching the program. If it finds the parent.lock file, it tries to delete it. If it's unsuccessful, it displays the "Mozilla is already in use" message, rather than launching the Profile Manager. That way, if a machine freezes and has to be restarted before Mozilla has a chance to close completely, the parent.lock file that is left behind should automatically be deleted before Mozilla is launched again.

If you encounter this message, the best thing to do is to restart the computer. A hidden instance of Mozilla may be holding the file open, and restarting the machine should release the file.

If this doesn't work, try to manually delete the parent.lock file out of the profile directory in h:\local\mozilla\ using the Windows File Manager.  

If this still doesn't work, your department's computer contact should send a note in to consult so we can determine why the file is being held open.

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