You have basically two choices (that i can think of)
- Launch firefox, and update your profile with the correct settings (proxy ones for example).
Then close and retrieve your configuration in
~myusername/.mozilla/firefox/xxxxxxx.default/prefs.js. xxxxx is a dynamic string. You can then use this user preferences for your deployement.
- Directly update that file, after you've deployed / installed a machine, with the proxy settings.
When you will launch firefox with that user, the settings will be directly applied.
According to the comment of @Sparhawk, the second option would fit better. In that case we keep the original
prefs.js as intact as possible, just changing the proxy settings:
user_pref("network.proxy.http", "IPADDRESS OR URL");