if then mkdir ~/.mozilla fi if then mkdir ~/.mozilla/plugins fi chmod -R 770 ~/.mozilla

This next command will create the plugins folder for your custom FF 51 install. A full list of ISO language-country codes available for FF 51 can be found here. The same logic applies to other languages. you want the Brazilian Portuguese version, replace en-US by pt-BR on the command above.

Note: the above command downloads FF 51 in United States' English ( en-US).

Now CLOSE ALL FIREFOX INSTANCES (windows) and then run this shell command, in order to download and install the FF 51 tarball and then remove the FF 51 auto updater: sudo killall firefox if then wget -O ~/applications/2 else wget -O ~/applications/2 fi cd ~/applications tar -xvf ~/applications/2 rm ~/applications/2 ~/applications/firefox/updater* Open a shell terminal window as a common user (not root / superuser!) and then run this command in order to create an 'applications' folder: mkdir ~/applications In case you wish to keep using the current (most up-to-date) version of Firefox but also install Firefox 51 (FF 51) in parallel, so you can use FF 51 when you need to use the JRE (Java NPAPI) plugin, you can follow these steps:

Java for firefox update