I have tried to install a special ATI driver using a method described in http://debianhelp.wordpress.com/2012/09/28/to-do-list-after-installing-ubuntu-13-04-aka-raring-ringtail-operating-system/ Details: Alternative ATI Legacy Video Driver PPA installation for (for < 5000 series cards): sudo apt-get remove --purge fglrx fglrx_* fglrx-amdcccle* fglrx-dev* sudo add-apt-repository ppa:makson96/fglrx sudo apt-get update sudo apt-get upgrade sudo apt-get install linux-headers-generic fglrx-legacy sudo aticonfig --initial And then reboot. There were a couple of warnings at "sudo apt-get install linux-headers-generic fglrx-legacy" with update-alternatives. But, at the last step I got "aticonfig: No supported adapters detected". Unity does not start anymore. I only can login to Gnome. How can I get back to a working system?