Why is Firefox/ Thunderbird telling me "already running", "profile in use" or "No running window found"?


  1. Change into your Mozilla profile directory:
    cd ~/.mozilla/firefox/<profile-name>.default/
    # For Example ~/.mozilla/firefox/torktynj.default/
  2. Check the lock file.
    ls -l lock
    lrwxrwxrwx 1 username stud 19 2013-03-20 16:02 lock ->
    # In this example the firefox instance is running on
    # which is tardis-a01.ee.ethz.ch
  3. Login to the given machine and kill any firefox process:
    ps -ef | grep firefox
    kill -9 <pid>
    # Example:
    # ps -ef | grep firefox
    # username  6060     1  0 Mar20 ?        00:01:23 firefox
    # kill -9 6060
  4. Remove any non deleted lockfile.
    rm ~/.mozilla/firefox/<profile-name>.default/lock
    rm ~/.mozilla/firefox/<profile-name>.default/.parentlock


  1. Check with the task manager if firefox/thunderbird is running, if yes, kill it.
  2. Delete the following file:

    W:\Application Data\Mozilla\Firefox\Profiles\<profile-name>\parent.lock

Mac OS X

  1. Check with the Activity Monitor if you have any dead firefox processes still lingering around. If so, kill them (Button labeled "Quit Process").
  2. Delete the following file:

    ~/Library/Application Support/Firefox/Profiles/<profile-name>/.parentlock


FAQ/FirefoxMessages (last edited 2021-09-27 06:53:19 by bonaccos)