I was using Ubuntu 14.04, after updating it to 15.10 using terminal I restarted the system. But then it started to boot into a Terminal similar to MS-DOS. And I've keyed in my credentials then the next prompt was " To run a command as admin (user'root'), use "sudo " ".
How can I solve this. I got important files in the hard drive.
I had the same problem occurring to me (Ubuntu 14.04 LTS). I thought it was because I was trying out startx -command with sudo.
Later I found out that the ~/.Xauthority -file was being owned by root, so at the login screen I hit ctrl+alt+f2 and from there I changed the ownership back to me (sudo chown user:user .Xauthority) and was able to login again.
