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It happened some minutes ago when I plugged my secondary monitor and my graphical interface simply crashed. So I had to restart my session. Since the crash Ubuntu insists to use Unity2D fall back instead of the default one. I used to plug the secondary monitor everyday when at home and nothing bad happened before.

This 2D version of the GUI is ugly and has a lot of problems. How can I go back to Unity 3D GUI?


update

It seems somehow I lost my opengl support (driver issues).

$ glxinfo

name of display: :0.0
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Error: couldn't find RGB GLX visual or fbconfig

Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".
Xlib:  extension "GLX" missing on display ":0.0".

And:

$ glxgears
Xlib:  extension "GLX" missing on display ":0.0".
Error: couldn't get an RGB, Double-buffered visual

update

$ lspci | grep VGA

00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)

How can I revert things and go back to the right driver?

share|improve this question
    
can you select unity3D on the login screen? Or does the fallback occur again? Most likely the driver switched to another one and you lost opengl support. Can you chack this with glxinfo and glxgears? –  Michael K Nov 15 '11 at 7:49
    
Exactly, when I choose unity3D I still get Unity2D when I login. It's happening because I lost OpenGL support (I checked it with the command /usr/lib/nux/unity_support_test -p). I'll update the question with the output of the commands. –  marcio Nov 15 '11 at 8:12
1  
Well update information on your graphics hardware and driver as well. –  Michael K Nov 15 '11 at 8:19
    
please run this in a terminal and add the resulting information to your question. lspci | grep VGA –  cprofitt Nov 15 '11 at 15:32
    
@cprofitt, take a look at the last question update. –  marcio Nov 15 '11 at 15:37

2 Answers 2

up vote 1 down vote accepted

Finally solved the problem here! Like @MichaelK said:

[...] Most likely the driver switched to another one and you lost opengl support [...] Well update information on your graphics hardware and driver as well.

So the way I found to reset things was to just purge and install xserver-xorg, after that everything went back to normal:

$ sudo apt-get purge xserver-xorg
$ sudo apt-get install xserver-xorg xserver-xorg-video-all
$ sudo reboot

Voila! Hope it helps.

ps: The only bad thing now is that every time I plug a secondary monitor on my computer (specially when showing Ubuntu to someone) I have to cross my fingers secretly. This driver switching behavior from Ubuntu is no good man ¬¬

share|improve this answer
    
Instead of reinstalling, a dpkg-reconfigure on the packages could do the trick without purging and reinstalling as well. –  Michael K Nov 16 '11 at 6:58
    
I tried it and the reconfigure command does not revert to functional behavior. The only real solution I found was reinstalling. –  marcio Jan 6 '12 at 21:16
sudo apt-get install libgl1-mesa-swrast

This will solve all your problems.

Then run sudo apt-get update and check with glxinfo and glxgears.

share|improve this answer
1  
Why run apt-get update after apt-get install ... rather than before? –  Eliah Kagan Jul 13 '12 at 18:42

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