I finally got around to running my updates and one of them was the new nvidia driver. it removed the gpu from the list of cuda devices in blender. installed nvidia-modprobe and restarted as per a web search. still not working.
GTX 560Ti xubuntu 12 x64
Cd to the ‘blender’ executable then run it as root with sudo just one time to enable cuda again . hopefully it works for you.
no dice. someone said reverting the driver back fixed it… i’d hate to get stuck on a certain driver revision. do I have to actually do a modprobe thing or put something in an init script somewhere. I havn’t had to mess with modprobe in like 10 years I don’t even remember anything about that lol. i’m ubuntu spoiled!
I have the same problem and running Blender as root doesn’t give the possibility to enable Cuda.
From the terminal you copy here what you get with the next commands, so that we know more details of your hardware and system:
lspci | grep -i vga
uname -r
cat /proc/driver/nvidia/version
sudo dpkg -l | grep -i nvidia
Did check yesterday - nvidia’s newest Beta NVIDIA-Linux-x86_64-346.22 does not compile and end up in error messages with either DKMS or 32 bit support selected or not. Last version working on GTX560 i have here is NVIDIA-Linux-x86_64-343.22.
02:00.0 VGA compatible controller: NVIDIA Corporation GK104 [GeForce GTX 760] (rev a1)
3.13.0-30-generic
NVRM version: NVIDIA UNIX x86_64 Kernel Module 331.113 Mon Dec 1 21:08:13 PST 2014
GCC version: gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1)
ii bbswitch-dkms 0.7-2ubuntu1 amd64 Interface for toggling the power on nVidia Optimus video cards
ii libcuda1-331 331.113-0ubuntu0.0.4 amd64 NVIDIA CUDA runtime library
ii nvidia-331 331.113-0ubuntu0.0.4 amd64 NVIDIA binary driver - version 331.113
rc nvidia-libopencl1-331 331.38-0ubuntu7 amd64 NVIDIA OpenCL Driver and ICD Loader library
ii nvidia-opencl-icd-331 331.113-0ubuntu0.0.4 amd64 NVIDIA OpenCL ICD
ii nvidia-prime 0.6.2 amd64 Tools to enable NVIDIA’s Prime
ii nvidia-settings 331.20-0ubuntu8 amd64 Tool for configuring the NVIDIA graphics driver
First of all for both you try with the official version of blender. Enter the website of Blender and download the tar.bz2 file according to the architecture of your system:
Open the file browser, extract the tar.bz2 contents to a folder and run (double-click) the “blender” file in that folder.
Thus rule out that this is a problem of CUDA libraries and Blender from Ubuntu repository that does not include the precompild CUDA kernel.
@VincentG, I’m not sure if from that version of the nvidia driver the “nvidia-modprobe” package is needed, but just in case you install this package:
http://packages.ubuntu.com/utopic/nvidia-modprobe
then reboot the system.
I was already using that package.
I also install nvidia-modprobe and after reboot Cuda is still not there in Blender.
I don’t know exactly when that happened but probably after a Ubuntu update. I’m using the 12.04 LTS (EDIT: 14.04) version.
Cuda is working well on my Windows session.
@ @VincentG Try to Install ‘nvidia-331-uvm’ looks like it’s missing.
Plus the kernel needs to be updated , latest is 3.13.0-43.
If all fails I suggest to upgrade to 14.04 LTS
Thanks. Unfortunately that doesn’t change.
I’m using the 14.04 version of Ubuntu, sorry, I made a mistake.
Oh… Cuda is back ! I don’t know when exactly, maybe it’s the nvidia packages you made me install that are finally working… 
People, to prevent problems of missing packages you remember installing drivers from the drivers manager or “Additional Drivers”. This will automatically install the necessary packages except “nvidia-modprobe”, that being this new change still have to install it manually.
shaun@Shauns-Desktop:~$ lspci | grep -i vga
01:00.0 VGA compatible controller: NVIDIA Corporation GF114 [GeForce GTX 560 Ti] (rev a1)
shaun@Shauns-Desktop:~$ uname -r
3.2.0-74-generic
shaun@Shauns-Desktop:~$ cat /proc/driver/nvidia/version
NVRM version: NVIDIA UNIX x86_64 Kernel Module 331.113 Mon Dec 1 21:08:13 PST 2014
GCC version: gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)
shaun@Shauns-Desktop:~$ sudo dpkg -l | grep -i nvidia
[sudo] password for shaun:
ii nvidia-304 304.125-0ubuntu0.0.0.1 NVIDIA binary Xorg driver, kernel module and VDPAU library
ii nvidia-331 331.113-0ubuntu0.0.0.3 NVIDIA binary Xorg driver, kernel module and VDPAU library
ii nvidia-common 1:0.2.44.2 Find obsolete NVIDIA drivers
ii nvidia-current 304.125-0ubuntu0.0.0.1 Transitional package for nvidia-current
ii nvidia-modprobe 340.24-1~ubuntu14.04.1 utility to load NVIDIA kernel modules and create device nodes
ii nvidia-settings 331.20-0ubuntu0.0.1 Tool for configuring the NVIDIA graphics driver
shaun@Shauns-Desktop:~$
not sure why I have 304 and 331 both installed
sudo apt-get install nvidia-331-uvm Fixed it. didn’t even have to reboot. apparently its a kernel module for nvidia memory management. Thanks @ramboblender
EDIT: fixed:
classic… so i tried to install modprob anyways, and now it works … :RocknRoll: classic situation of “whining will solve it” situation i guess… :doh: 
Thanks for the link @YAFU (http://packages.ubuntu.com/utopic/nvidia-modprobe)
I’m going nuts over this issue… None of the fixes i find will do it…
This didn’t help… all packages are there, including nvidia-331-uvm… but no cuda…
01:00.0 VGA compatible controller: NVIDIA Corporation GK104 [GeForce GTX 770] (rev a1)
3.13.0-44-lowlatency
NVRM version: NVIDIA UNIX x86_64 Kernel Module 331.113 Mon Dec 1 21:08:13 PST 2014
GCC version: gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1)
ii bbswitch-dkms 0.7-2ubuntu1 amd64 Interface for toggling the power on nVidia Optimus video cards
ii libcuda1-331 331.113-0ubuntu0.0.4 amd64 NVIDIA CUDA runtime library
ii nvidia-331 331.113-0ubuntu0.0.4 amd64 NVIDIA binary driver - version 331.113
ii nvidia-331-uvm 331.113-0ubuntu0.0.4 amd64 NVIDIA Unified Memory kernel module
ii nvidia-libopencl1-331 331.113-0ubuntu0.0.4 amd64 NVIDIA OpenCL Driver and ICD Loader library
ii nvidia-opencl-icd-331 331.113-0ubuntu0.0.4 amd64 NVIDIA OpenCL ICD
ii nvidia-prime 0.6.2 amd64 Tools to enable NVIDIA’s Prime
ii nvidia-settings 331.20-0ubuntu8 amd64 Tool for configuring the NVIDIA graphics driver
Also, there is no nvidia-modprobe for 14.04, only for 14.10…
lost and confused at hair minus 3million units 
what am i doing wrong?!?! :spin:
Thankfull for any hint…
I know about another solution. You could install Nvidia driver manually from Nvidia official website.