a tumblelog
05 Jul 2019

A copy of Thunderbird is already open

In the afternoon I had to force quit Thunderbird on my Mac Mini running MacOS Mojave. When I tried to restart Thunderbird I was greeted with the following message:

A copy of Thunderbird is already open warning dialog

A copy of Thunderbird is already open. Only one copy of Thunderbird can be open at a time.

The fix for this is easy: deleting the lock file that Thunderbird has left behind when I killed it.

First, I opened the terminal and changed into Thunderbird's Profiles directory:

cd ~/Library/Thunderbird/Profiles

Next, I used ls -1 to find the name of my default profile directory, which reported:


I changed into this directory and deleted the file named .parentlock:

cd jt1wxigb.default/
rm .parentlock

And finally I restarted Thunderbird, successfully this time.