NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver.

Accelerated Computing CUDA CUDA Setup and Installation
1

Running System: Arch Linux with Gnome on Xorg (X11).
Hardware: GT820M
Trying to run command: nvidia-smi
Error:

NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver.  
Make sure that the latest NVIDIA driver is installed and running.

packages installed

pacman -Q | grep nvidia

nvidia 418.56-7
nvidia-settings 418.56-1
nvidia-utils 418.56-1
opencl-nvidia 418.56-1

pacman -Q | grep cud 

cuda 10.1.105-11

LOG FILE (nvidia-bug-report.log): https://pastebin.com/DxNV7eTu
UPDATE: see attachments

P.s

nvidia-settings

ERROR: NVIDIA driver is not loaded
ERROR: Unable to load info from any available system

nvidia-bug-report.log.gz (52.2 KB)

2

gt 820 m is a fermi GPU

The last CUDA version supporting it was CUDA 8.0

3

And what driver version should I install?
Is there any kind of table or something?

4

Install the driver that comes with the CUDA 8.0 toolkit installer.

Table:

[url]Release Notes :: CUDA Toolkit Documentation

scroll down to table 1

5

Last question, which run file should I download for arch linux?
[url]https://developer.nvidia.com/cuda-80-ga2-download-archive[/url]

6

arch linux is not a supported environment for CUDA