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An automatic update ran yesterday (7/7/2015) and now I am locked out of X windows. The login screen has gone extra large, so the login box takes up a large part of the screen. When I try and log in it accepts the password, then dumps me back to the login screen. I can switch to the terminal with ctrl-alt-F1 and log in OK so there is no issue with my password, but then I am stuck in text mode.

How do I fix this?

Update:

I think I found the cause in syslog:

Xlib: extension "GLX" missing on display:
gnome-session-is-accelerated: No hardware 3D support
gnome-session-check-accelerated: Helper exited with code 256
gnome-session[...]: CRITICAL: We failed, but the fail whale is dead. Sorry...
lightdm[...]: ** lightdm CRITICAL **: session_get_login1_session_id: assertion 'session!=NULL' failed

So it appears that it is failing because it is not getting 3D acceleration, despite having an Nvidia GTX 960 card.

But I still have no idea how to fix it.

Zanna
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Dave Kirby
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1 Answers1

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I just had the same problem and fixed it by removing all nvidia drivers:

sudo apt-get purge nvidia-*

(The glob didn't expand here so you might need to type them all..)

Booting with nouveau.modeset=0 added to the linux line in the grub. (Press E at the grub menu entry and add the text)

Login in to the system, right clicking for at terminal and running:

dconf reset -f /org/compiz/

and

setsid unity

After this I reinstalled the nvidia drivers via the additional drivers menu.

Hope it helps!

user270819
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