Ah, but the important part is that it gets copied 'at some point'. If you try to copy the prefs.js or append to it in /home/morph/.mozilla/firefox you will actually end up creating all the directories from .mozilla down and they will have root owner and group. When Firefox starts up and tries to access the morph profile it will act like the profile is already in use and you won't be able to do anything. You can't use the existing modified profile and you can't create a new one because firefox running under user morph does not have permission to write to those directories. You can put a script in /exec to change the owner and group but now you are talking about placing the whole user profile there. It added about 15 to 20 seconds to the boot time to copy the whole profile to /home/morph/.mozilla and you will also have to make the profile on your workstation first. That means creating a user morph, logging in as morph, start firefox to get a profile created, then copy it to the distro /copy directory. You will have to run a script to change the owner and group, etc. The easiest reliable solution is to have firefox create an initial profile, modify it however you want, then run firefox.

I tried putting the profile in the /home/morph directory of the source but it wasn't there after the CD booted. I guess the overlay filesystem doesn't include the /home directory. I was reading about cowloop being able to overlay the whole file system and allow read access to everything and store writes on the ramdisk but I don't think it is released on LiveCD yet. I could be wrong and also I don't know much about it.