NVIDIA freezes if xserver is not running

[GuillaumeDesforges]

Describe the bug I am trying to setup a server with a GPU for my computations. I am using this server remotely.

If I install nvidia using the settings

nixpkgs.config.allowUnfree = true;
services.xserver.videoDrivers = [ "nvidia" ];

And then run

nvidia-smi

I get a proper output but then the console freezes. I can open a new ssh connection so it does seem like the server crashes though.

If I setup with xserver enabled like this:

nixpkgs.config.allowUnfree = true;
services.xserver.enable = true;
services.xserver.layout = "fr";
services.xserver.xkbOptions = "eurosign:e";
services.xserver.videoDrivers = [ "nvidia" ];

then everything works fine, nothing hangs and I can use other GPU related processes like PyTorch.

To Reproduce Steps to reproduce the behavior:

1. On unstable channel
2. Set the /etc/nixos/configuration.nix as described above.

Expected behavior nvidia-smi and other GPU related processes should not hang.

Metadata

$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 5.4.22, NixOS, 20.09pre215024.e97dfe73bba (Nightingale)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.3`
 - channels(root): `"nixos-20.09pre215024.e97dfe73bba"`
 - channels(arsleust): `""`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module:

[kolbycrouch]

Maybe this has something to do with hardware.opengl.enable. It's automatically set to true when you declare services.xserver.enable = true AFAIK.

[GuillaumeDesforges]

Would it help if I tried rebuilding NixOS with:

services.xserver.enable = false;
hardware.opengl.enable = true

?

[kolbycrouch]

@GuillaumeDesforges Try it, I don't think it could hurt.

I'm not very familiar with all of this, but the docs for hardware.opengl.enable say that it's needed for 3d acceleration and is automatically turn on as a dependency of certain modules ( x11 & wayland WM's ). I'm assuming that it's set as "false" in your case since your not using x11.

[GuillaumeDesforges]

This did not fix the issue.

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