Firefox: where does user.js go?

[technossomy]

To supercede the prefs.js file settings, the recommendation from Mozilla is to use a custommade user.js file and place it in the same location as the prefs.js file. That is not as simple as it sounds, because the prefs.js file is placed in the following location:
[user]/.mozilla/firefox/_some_name.default
The "_some_name" part is different for every machine the application is installed on, so upon an automated installation, where would be the best place to leave a standard user.js file?

[blinky]

<firefox_installation_dir>/defaults/profile

[technossomy]

Thank you for your response. The firefox installation directory is /usr/local/bin?

EDIT: I just noticed the following source: Profile folder - Firefox - MozillaZine Knowledge Base
I will experiment some more and get back with issues, if any.

[blinky]

Thats probably the script to start firefox. On rpm based systems you can do:

rpm -ql firefox

that will show you where firefox is actualy installed (in fedora its /usr/lib/firefoxxxx)

You need to find the actual installation directory for your distribution.

[technossomy]

Cant figure this one out. The installation directories are listed here:
Installation directory - MozillaZine Knowledge Base
I run FreeBSD and there is no /usr/lib/firefox or /usr/lib64/firefox directory. I was under the impression that there is a profile directory which should be used to hold such preference files?