# CUDA error after sudo apt-get update. UserWarning: CUDA initialization: CUDA unknown error....return torch.\_C.\_cuda\_getDeviceCount() \> 0

**URL:** <https://deeptalk.lambda.ai/t/cuda-error-after-sudo-apt-get-update-userwarning-cuda-initialization-cuda-unknown-error-return-torch--c--cuda-getdevicecount-0/2343>\
**Category:** Technical Help\
**Created:** [May 5, 2021, 5:22pm UTC](https://deeptalk.lambda.ai/t/cuda-error-after-sudo-apt-get-update-userwarning-cuda-initialization-cuda-unknown-error-return-torch--c--cuda-getdevicecount-0/2343 "2021-05-05T17:22:38Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![yseeker](https://sea1.discourse-cdn.com/flex019/user_avatar/deeptalk.lambda.ai/yseeker/32/614_2.png) [@yseeker](https://deeptalk.lambda.ai/u/yseeker)\
**Post date:** [May 5, 2021, 5:22pm UTC](https://deeptalk.lambda.ai/t/cuda-error-after-sudo-apt-get-update-userwarning-cuda-initialization-cuda-unknown-error-return-torch--c--cuda-getdevicecount-0/2343/1 "2021-05-05T17:22:38Z")

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Hello,  
To set up the Pytorch and Tensorflow environment, I did a fresh install of ubuntu 20.04 and installed the lambda stack. The installation went without any errors nvndia-smi shows 460.73.01 and CUDA 11.2. However, I got the following error.

torch.cuda.is\_available()

/usr/lib/python3/dist-packages/torch/cuda/ **init**.py:52: UserWarning: CUDA initialization: CUDA unknown error - this may be due to an incorrectly set up environment, e.g. changing env variable CUDA\_VISIBLE\_DEVICES after program start. Setting the available devices to be zero. (Triggered internally at …/c10/cuda/CUDAFunctions.cpp:109.)  
return torch.\_C.\_cuda\_getDeviceCount() \> 0  
False

I found a similar issue in this topic [CUDA pytorch not working on a fresh install RTX 3070 - Technical Help - DeepTalk - Deep Learning Community](https://deeptalk.lambda.ai/t/cuda-pytorch-not-working-on-a-fresh-install-rtx-3070/2203), and I tried again a fresh install of ubuntu 20.04 and installed the lambda stack.  
Then the torch.cuda.is\_available() returned True, and apparently worked fine for a while but after running

sudo apt-get update && sudo apt-get dist-upgrade  
sudo reboot

the torch.cuda.is\_available() threw the same error (i.e., UserWarning: CUDA initialization: CUDA unknown error…return torch.\_C.\_cuda\_getDeviceCount() \> 0).

What can I do to fix this issue?

The followings are the details of my environment.

PyTorch version: 1.8.1  
CUDA used to build PyTorch: 11.1

OS: Ubuntu 20.04.2 LTS (x86\_64)  
GCC version: (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0  
CMake version: version 3.16.3

Python version: 3.8 (64-bit runtime)  
CUDA runtime version: 11.1.105  
GPU models and configuration: GPU 0: GeForce GTX 960  
Nvidia driver version: 460.73.01

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<div class="post-metadata">

**Author:** ![yseeker](https://sea1.discourse-cdn.com/flex019/user_avatar/deeptalk.lambda.ai/yseeker/32/614_2.png) [@yseeker](https://deeptalk.lambda.ai/u/yseeker)\
**Post date:** [May 6, 2021, 11:14pm UTC](https://deeptalk.lambda.ai/t/cuda-error-after-sudo-apt-get-update-userwarning-cuda-initialization-cuda-unknown-error-return-torch--c--cuda-getdevicecount-0/2343/2 "2021-05-06T23:14:58Z")

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Disabling the secure boot just before installing the lambda stack solved the issue.