Login Failure( redirects to login after enterning password ) in Ubuntu 14.04

Question

I'm unable to login to my account in Ubuntu. The login Screen appears and I choose me root account, enter the password and press enter. But unfortunately a black screen is displayed for couple of seconds and than I'm redirected to login again and again. I'm sure my password is right. Also I can use the guest session.
How can I resolve this bug? I don't want to reinstall whole Ubuntu again. That will be my last option.
Thanks in Advance

Answer 1

What was the last action you did in your Ubuntu? Most of the time login loop is happening due to some action which didn't completed successfully. I experienced login loop due to graphics card driver releated issue as mentioned here

Answer 2

Try the following in case it is an issue due to nvidia graphics card driver issue.

1. Switch to a virtual terminal Ctrl+Alt+F1-6 and run:

   sudo apt-get install xfce4
   sudo service lightdm restart
   

2. Select xfce instead of unity and log in.

   sudo apt-get purge nvida-*
   sudo add-apt-repository ppa:graphics-drivers/ppa
   sudo apt-get update
   sudo apt-get install nvidia-361 nvidia-prime
   sudo add-apt-repository ppa:nilarimogard/webupd8
   sudo apt-get update
   sudo apt-get install prime-indicator
   

3. reboot and log into xfce again

4. prime-indicator
5. switch to the intel card (you may have to log out manually)
6. Log in using unity (this will use the intel card).