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Ubuntu – After Upgrade from 14.04 to 16.04 login screen runs in a loop while console login works

14.0416.04loginlogin-screenupgrade

I am on a DELL Precision 5510 Ubuntu Edition with Ubuntu 14.04 as default installation. Today I upgraded from 14.04. to 16.04 as shown here

The upgrade went without any error messages. However, after reboot I cannot login via Login Manager (lightdm by default?) anymore. While the password is accepted, the screen shortly prompts the desktop view for, say, a second and then immediately switches back to the login screen without further notice.

I can properly login via text console ( CTL + ALT + F1). So it is definitely not a password wrong issue.

I have read that this might have happened users before, see here. Difference with me is, that the screen after the login attempt is not completely black but it actually shows the desktop overview and even a system dialogue which I can't access because the loop follows to quickly.

What could be wrong here? How can I use my system again? Any help is much appreciated.

Best Answer

I ran into this after updating from 15.10 Wily Werewolf.

I use Nvidia's prime-select command to enable and disable the dedicated graphics card. (After using Ctrl+Alt+F1 and logging into the console) I disabled my GT 540M graphics card with sudo prime-select intel followed by sudo reboot. Upon reboot I was able to log into Unity.

Obviously this is more of a short-term fix and as the other answers have indicated, perhaps the long term solution will be related to replacing or upgrading the Nvidia drivers or allowing the existing unsigned driver to run by disabling secure boot. But hopefully this at least gets you to the desktop!

Edit: The Nvidia driver can now be installed using the official PPA, per this answer:

sudo apt purge nvidia-*
sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt update
sudo apt install nvidia-364

Related Solutions

Ubuntu – Login Loop for Guest Account only on 16.04

While it may not be perfectly complete answer to this general query, a response to another more specific question I posted covers what I needed to know about the differences between the handling of guest accounts in 14.04 to 16.04 [ https://askubuntu.com/a/771284/534729 ]

Ubuntu – Stuck in login ubuntu 14.04 after trying everything

It's a temporary answer:

The problem I was experiencing is after recent upgrade, instantly past login I was logged in and then redirected back to login screen.

I've used this: Is there any way to roll back the most recent upgrade? to roll back most recent upgrade. I've rolled back unity, it didn't help, then I rolled back nvidia-304 and it helped.

Edit: After update I was struck again with the same problem and found a simpler solution here in comments http://www.linuxslaves.com/2016/05/3-ways-fix-ubuntu-gets-stuck-login-loop.html

I will past the relevant part of the comment by Foxjt:

The general consensus seemed to rotate around problems with the video drivers, so:

sudo ubuntu-drivers devices

This shows the required drivers for my Video card (nVidia G96 GeForce 9400 GT) as nvidia-340.

I ran:

sudo apt-get install nvidia-340

The messages showed that nvidia-304 was being removed and replaced with nvidia-340.

After a reboot, I was able to finally login!!! Hooray!!!

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