Firefox and thunderbird fail to start

After a Linux desktop has been rebooted unexpectedly firefox or thunderbird sometimes won't start. Do the following to fix the problem with firefox.

cd
cd .mozilla
cd firefox

Now enter

ls -l

You will see one or two files and one oddly named directory something like this

drwx------ 6 sysman sysman 1024 Feb 15 16:03 3tprextl.default
-rw-r----- 1 sysman sysman   94 Feb 15 16:03 profiles.ini

In this case the directory is called 3tprextl.default. Two files, lock and .parentlock need to be deleted.

cd 3tprextl.default
rm lock .parentlock

You should now be able to start firefox. You will probably be asked whether you want to start a new session or restore the previous one. Starting a new session is usually the best choice.

To fix a similar problem with thunderbird you need to remove the lock and .parentlock files found in the thunderbird configuration directory which is usually stored in ~/.thunderbird.