To add a repository ppa: sudo add-apt-repository ppa:user/ppa-name sudo apt-get update Sometimes adding a repository may result in error related to missing key. Then copy that key and run following command sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com KEY Do this for each of the missing keys. Now re-run the above two commands. If you are under proxy network or seen a error like Cannot add PPA: 'ppa:user/ppa-name'. Please check that the PPA name or format is correct. and if you are sure that the PPA is working, the try sudo -E add-apt-repository ppa:user/ppa-name