I am a Ubuntu newbie. I am running Ubuntu 16.04. Until yesterday my computer was fine. But today it got stuck in a login loop. I enter my username and password, it lets me to log in, but after a few seconds, it goes back to the log in screen. It keeps repeating forever. I went through the Ubuntu forums. They have suggested to login using Ctrl+Alt+f1 and then run mv .Xauthority Xauthority.backup. The problem is when I executed Ctrl+Alt+f1, a progress bar is shown forever and it never opens the terminal. I am not sure what to do next. Any help is greatly appreciated.