If Firefox is already installed remove with following commands
For ubuntu
sudo apt-get remove firefox
For centos
sudo yum remove firefox
after uninstalling firefox unlink or rename the current firefox binary as below
unlink /usr/bin/firefox
Take backup of previously configured firefox as below
mv /usr/bin/firefox /usr/bin/firefox_bak
Download latest Firefox
Download the firefox in to particular folder as below
cd /opt
wget http://ftp.mozilla.org/pub/firefox/releases/67.0/linux-x86_64/en-US/firefox-67.0.tar.bz2
Extract the archive using the following command.
tar xvjf firefox-67.0.tar.bz2
Installation of Firefox In Ubuntu and Centos
Installation of firefox means to create a soft-link of Firefox binary file to systems bin directory to make it accessible from anywhere in the system.
sudo ln -s /opt/firefox/firefox /usr/bin/firefox
Now you can open firefox from terminal by below command or you can open through GUI
firefox &