I accidentally messed up the permissions by typing sudo chown -R root:root /usr. It was supposed to usr instead of /usr. anyway, I lost sudo function and showed the error message sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set. But I followed this thread https://askubuntu.com/a/471503/1127900 and solved that issue.
But after that I rebooted and tried to login my user. After typing the password I am getting the login window again and again, but no password incorrect message. But login using tty3 is a success.
Please help to fix this problem. I am in a severe headache with this.
Many thanks in advance
