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I know this bug in variations has been discussed in other questions, but none of the solutions work...

I'm running Ubuntu on a lenovo ThinkPad T420s. It has a Nvidia Optimus discrete graphics card.

I need the Nvidia drivers in order to program in CUDA, and EVERYTHING WORKED in Ubuntu 12.04.

After upgrading to 12.10, launcher disappeared. Tried to fix by activating Unity plugin through ccsm and various other solutions, nothing worked. In the end, I just used the Gnome environment. Once again, everything worked.

Not having yet learned my lesson, I eagerly upgraded to 13.04 because I missed Unity and was hoping it would magically work. And guess what? It did! Unity was working fine...

Then I tried running a CUDA 'helloworld' type program, and it seg faulted. This was strange, as the program itself was fine and had never segfaulted before. I surmised something was wrong with the graphics card drivers, so I tried:

  • removing Bumblebee (I know this was kind of random but I wanted to give it a fresh start)
  • reinstalling nvidia-common

And voila! CUDA worked.

However, on reboot I found that Unity had disappeared again! Grrr. Once again, reactivating Unity plugin from ccsm has no effect, nor do other solutions discussed on this site, e.g. everything here:

Unity is broken after upgrading to 12.10 (Optimus laptop)

I've tried disabling Optimus in the BIOS, and purging and reinstalling nvidia drivers... but I can't figure out how to get Unity back. And to top it off, they disabled the Gnome fallback in 13.04!!

So, I'm really confused right now, since IT DID WORK immediately after install 13.04. I suspect that the answer must lie in some combination of:

Nvidia driver use Optimus use in BIOS Bumblebee integration

But I can't figure it out.

I have some error messages which may help.

I reinstalled Bumblebee, and when I run optirun:

[ERROR]Cannot access secondary GPU - error: [XORG] (EE) No devices detected.

When I, out of curiosity, ran the command 'unity':

... Ok, that's odd. It threw errors last time, but this time it didn't.

Alright, I tried enabling unity again in ccsm and restart lightdm, and lo and behold it worked. Unity has returned.

However, CUDA is still broken, and I'm kind of afraid to try reinstalling the nvidia-common drivers now.

Any suggestions? If there's some commands I can run to get useful information about my system setup, please comment and I will run them and post the output.

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closed as off-topic by Richard, Jorge Castro, Braiam, Warren Hill, Ask Apr 14 at 6:38

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