NVIDIA

Determining the type of your GPU

• MXM / output-providing card (shows as VGA Controller in lspci), i.e. graphics card in desktop computer or in some laptops
• muxless/non-MXM Optimus cards have no display outputs and show as 3D Controller in lspci output, seen in most modern consumer laptops

MXM cards allow you to use the Nvidia card standalone, in Non-Optimus mode. Non-MXM cards require Optimus, Nvidia's integrated-vs-discrete GPU switching technology.

Non-Optimus mode

You need an MXM card (see above) for Non-Optimus mode. Follow NVIDIA Graphics Cards section in official manual.

In case of laptop you may also need to use a BIOS option to select which card to use for the internal display.

Optimus

Mostly useful for laptops. There are currently two solutions available under NixOS, described in detail below:

• Official solution: Nvidia PRIME (in on-demand "offload" mode, and always-on "sync" mode)
• Previous open-source solution: Bumblebee (now deprecated)

Nvidia PRIME

Official solution by nvidia. Currently, reverse PRIME does not work. The consequence of this is that if you have a special laptop configuration where external display ports are only exposed to the dedicated GPU, then running in offload mode will not allow you to use those display ports for external monitors. If you wish to use the external monitors in that particular case, you have to use sync mode.

offload mode

Currently only in unstable, to be included in 20.09 (see #66601).

In this mode the Nvidia card is only activated on demand, however a Nvidia card of the Turing generation or newer and an Intel Coffee Lake chipset is required for a complete poweroff of the Nvidia card (see discussion).

when you run program(s) with specific environment variables, i.e., here's a sample script called nvidia-offload that you can run wrapped around your exacutable, for example nvidia-offload glxgears:

nvidia-offload

export __NV_PRIME_RENDER_OFFLOAD=1
export __NV_PRIME_RENDER_OFFLOAD_PROVIDER=NVIDIA-G0
export __GLX_VENDOR_LIBRARY_NAME=nvidia
export __VK_LAYER_NV_optimus=NVIDIA_only
exec -a "$0" "$@"

To configure Offload mode, you firstly you need to enable the proprietary Nvidia driver:

/etc/nixos/configuration.nix

{
  services.xserver.videoDrivers = [ "nvidia" ];
  ...

Note that on certain laptops and/or if you are using a custom kernel version, you may have issues with your NixOS system finding the primary display. In this case you should also specify "modesetting" in videoDrivers as well, i.e.:

/etc/nixos/configuration.nix

 	
{
  services.xserver.videoDrivers = [ "modesetting" "nvidia" ];
  ...

Then you need to setup the Bus ID's of the cards as seen below.

Note: Bus ID is important and needs to be formatted properly

The Nvidia driver expects the bus ID to be in decimal format; However, lspci shows the bus IDs in hexadecimal format.

You can convert the value by:

• Stripping any leading zeros from the bus numbers or if the number is above 09, convert it to decimal and use that value.
• Replacing any full stops with colons.
• Prefix the final value with "PCI".

For example:

Output from lspci

09:1f.0 VGA compatible controller: NVIDIA Corporation Device 1f91 (rev a1)

Converted and correct format

PCI:9:31:0

A possible configuration:

/etc/nixos/configuration.nix

{ pkgs, ... }:

let
  nvidia-offload = pkgs.writeShellScriptBin "nvidia-offload" ''
    export __NV_PRIME_RENDER_OFFLOAD=1
    export __NV_PRIME_RENDER_OFFLOAD_PROVIDER=NVIDIA-G0
    export __GLX_VENDOR_LIBRARY_NAME=nvidia
    export __VK_LAYER_NV_optimus=NVIDIA_only
    exec -a "$0" "$@"
  '';
in
{
  environment.systemPackages = [ nvidia-offload ];

  services.xserver.videoDrivers = [ "nvidia" ];
  hardware.nvidia.prime = {
    offload.enable = true;

    # Bus ID of the Intel GPU. You can find it using lspci, either under 3D or VGA
    intelBusId = "PCI:0:2:0";

    # Bus ID of the NVIDIA GPU. You can find it using lspci, either under 3D or VGA
    nvidiaBusId = "PCI:1:0:0";
  };
}

sync mode

In this mode the Nvidia card is turned on constantly, having impact on laptop battery and health.

Possible issues:

• Hangs of applications after resume from suspend
• Wrong DPI calculation (in this case provide dpi manually services.xserver.dpi = 96;)
• Black screen after system upgrade (e.g. nixos-rebuild swtich; use nixos-rebuild boot instead and reboot)
• No video playback acceleration available (vaapi)

Example for NixOS 20.03

/etc/nixos/configuration.nix

{
  services.xserver.videoDrivers = [ "modesetting" "nvidia" ];
  hardware.nvidia.optimus_prime = {
    enable = true;

    # Bus ID of the NVIDIA GPU. You can find it using lspci, either under 3D or VGA
    nvidiaBusId = "PCI:1:0:0";

    # Bus ID of the Intel GPU. You can find it using lspci, either under 3D or VGA
    intelBusId = "PCI:0:2:0";
  };
}

Example for NixOS 20.09/unstable

/etc/nixos/configuration.nix

{
  services.xserver.videoDrivers = [ "modesetting" "nvidia" ];
  hardware.nvidia.prime = {
    sync.enable = true;

    # Bus ID of the NVIDIA GPU. You can find it using lspci, either under 3D or VGA
    nvidiaBusId = "PCI:1:0:0";

    # Bus ID of the Intel GPU. You can find it using lspci, either under 3D or VGA
    intelBusId = "PCI:0:2:0";
  };
}

Bumblebee

Deprecated solution. You should use offload mode instead.

Use option

hardware.bumblebee.enable = true;

non-NixOS case

• The nixGL project provides wrapper to use GL drivers outside of NixOS. You need to have nvidia drivers installed on your distro (for kernel modules). Then supply nvidia driver version you use on host system to nixGL.

CUDA

There some possible ways to setup a development environment using CUDA on NixOS. This can accomplished in the following ways:

• By making a FHS user env

cuda-fsh.nix

{ pkgs ? import <nixpkgs> {} }:

let fhs = pkgs.buildFHSUserEnv {
        name = "cuda-env";
        targetPkgs = pkgs: with pkgs;
               [ git
                 gitRepo
                 gnupg
                 autoconf
                 curl
                 procps
                 gnumake
                 utillinux
                 m4
                 gperf
                 unzip
                 cudatoolkit
                 linuxPackages.nvidia_x11
                 libGLU libGL
		 xorg.libXi xorg.libXmu freeglut
                 xorg.libXext xorg.libX11 xorg.libXv xorg.libXrandr zlib 
		 ncurses5
		 stdenv.cc
		 binutils
                ];
          multiPkgs = pkgs: with pkgs; [ zlib ];
          runScript = "bash";
          profile = ''
                  export CUDA_PATH=${pkgs.cudatoolkit}
                  # export LD_LIBRARY_PATH=${pkgs.linuxPackages.nvidia_x11}/lib
		  export EXTRA_LDFLAGS="-L/lib -L${pkgs.linuxPackages.nvidia_x11}/lib"
		  export EXTRA_CCFLAGS="-I/usr/include"
            '';
          };
in pkgs.stdenv.mkDerivation {
   name = "cuda-env-shell";
   nativeBuildInputs = [ fhs ];
   shellHook = "exec cuda-env";
}

• By making a nix-shell

cuda-shell.nix

{ pkgs ? import <nixpkgs> {} }:

pkgs.stdenv.mkDerivation {
   name = "cuda-env-shell";
   buildInputs = with pkgs;
                  [ git gitRepo gnupg autoconf curl
                    procps gnumake utillinux m4 gperf unzip
                    cudatoolkit linuxPackages.nvidia_x11
                    libGLU libGL
                    xorg.libXi xorg.libXmu freeglut
                    xorg.libXext xorg.libX11 xorg.libXv xorg.libXrandr zlib 
                    ncurses5 stdenv.cc binutils
                   ];
   shellHook = ''
      export CUDA_PATH=${pkgs.cudatoolkit}
      # export LD_LIBRARY_PATH=${pkgs.linuxPackages.nvidia_x11}/lib:${pkgs.ncurses5}/lib
		  export EXTRA_LDFLAGS="-L/lib -L${pkgs.linuxPackages.nvidia_x11}/lib"
		  export EXTRA_CCFLAGS="-I/usr/include"
   '';          
}

See also

• nixos-cuda-example
• nix-shell envs for Cuda
• CUDA setup on NixOS