Installing add-ons globally on Firefox
Most often when creating different profiles in Firefox, you use them for various things. One profile might have all the web-developer tools and add-ons you need in order to be your geeky self, while profile number two has your gamer-add-ons, which you don’t want to mix. But what if you want certain add-ons to be global? So when you do create a second profile, you won’t have to reinstall the same add-on twice, or more. The answer? Installing things through the command line.
For instance, let’s take the add-on AdBlock Plus. Great add-on. I for one want it on every Profile. So instead of doing it through the browser-interface, installing it once for every profile, do it through the command line, globally.
Become root and grab the add-on: