Transmission is a free BitTorrent client with a simple interface, Ubuntu comes bundled with Transmission in the official build, Transmission is set as the default BitTorrent client for Ubuntu. However the version of Transmission bundled with Ubuntu is not always latest depending on the Ubuntu distribution version, we can get the latest stable version of Transmission using the official transmissionbt ppa, This PPA will download the latest stable version Transmission depending on the Ubuntu version you are using.
Adding the official ppa to the local repository database.
sudo add-apt-repository ppa:transmissionbt/ppa
Update your local repository database.
sudo apt-get update
sudo apt-get upgrade
If you have removed Transmission and want to reinstall it or if you have installed an Ubuntu based distribution that does not come bundled with Transmission.
sudo apt-get install transmission-gtk