Forrest Jacobs

I recently set up a new Windows machine for gaming, but I’m actually using it more to play around with Linux via WSL. I set up NixOS on WSL using the aptly named NixOS on WSL project, but ran into a few issues during setup that bricked my environment¹. Below are the steps that ended up working for me in the end:

Goals

• Set up NixOS in WSL 2 on a new Windows 11 install (version 22H2.)
• Reuse my flake-based configuration from my other NixOS 22.11 installations.
• Take advantage of native systemd support in WSL.

Step 1: Install WSL 2

Per Microsoft’s documentation:

1. Open PowerShell as an admin by right-clicking on it and selecting “Run as administrator.”

2. Run wsl --install

Step 2: Install NixOS

Per NixOS-WSL’s documentation:

3. Download the installer listed in NixOS-WSL’s 22.05 release.

4. Move the file where you want your NixOS installation to live. I put it in C:\Users\<my username>\AppData\Local\NixOS, which I think follows Windows’s conventions.

5. Open PowerShell as a normal user, change to the directory you just made, and run wsl --import NixOS . nixos-wsl-installer.tar.gz --version 2

6. Run wsl -d NixOS to start NixOS. It’ll run through initial setup, then hang on “Starting systemd…” Press Ctrl + C to get back to PowerShell, and then run wsl --shutdown followed by wsl -d NixOS to get back into NixOS.

Step 3: Configure NixOS

At this point you should have a basic NixOS 22.05 installation! Let’s finish up by setting a username, switching over to flakes, updating to NixOS 22.11, and enabling native systemd:

7. Edit /etc/nixos/configuration.nix and make the following changes. Use sudo or some such to edit the file as root. You may want to nix-shell -p your favorite editor at this point – maybe Helix?

   • Change wsl.defaultUser to your desired username, and add something like users.users.<your username>.isNormalUser = true;
   • Remove references to ./nixos-wsl since we’ll set NixOS-WSL as a flake input:

       { lib, pkgs, config, modulesPath, ... }:
     -
     - with lib;
     - let
     -   nixos-wsl = import ./nixos-wsl;
     - in
       {
         imports = [
           "${modulesPath}/profiles/minimal.nix"
     -
     -     nixos-wsl.nixosModules.wsl
         ];
     

   • Add wsl.nativeSystemd = true;
   • Add networking.hostName, and set it to your Windows 11 “Device name.” You can find this in the Windows Settings app under System > About.

8. Add /etc/nixos/flake.nix as root with contents like the following. Replace <host-name> with your actual host name from configuration.nix.

   {
   
     inputs = {
       nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.11";
       NixOS-WSL = {
         url = "github:nix-community/NixOS-WSL";
         inputs.nixpkgs.follows = "nixpkgs";
       };
     };
   
     outputs = { self, nixpkgs, NixOS-WSL }: {
       nixosConfigurations."<host-name>" = nixpkgs.lib.nixosSystem {
         system = "x86_64-linux";
         modules = [
           { nix.registry.nixpkgs.flake = nixpkgs; }
           ./configuration.nix
           NixOS-WSL.nixosModules.wsl
         ];
       };
     };
   
   }

9. Run sudo nixos-rebuild switch

10. exit out of NixOS, then run wsl --shutdown followed by wsl -d NixOS. You should be logged in as the new default user.

11. At this point you should have a stable base to make any configuration changes you’d like.

Step 4: Cleaning up

• Rename wsl.automountPath to wsl.wslConf.automount.root in configuration.nix to match NixOS-WSL’s latest configuration.
• Delete the now unused /etc/nixos/nixos-wsl directory.
• Delete /home/nixos since you’ve changed your username.
• You can run sudo nix-channel --remove nixos if you don’t want the channel hanging around now that we’re using flakes.

Addendum: Share .ssh directory with Windows

It turns out that file permissions set in WSL are preserved in NTFS². You can store your SSH configuration files in Windows, and still use them from WSL with no permissions issues:

• Set up your ~/.ssh in NixOS like normal.
• Move your ~/.ssh directory to Windows with mv ~/.ssh /mnt/c/Users/<your Windows username>/.ssh
• Soft link it back to your WSL VM with ln -s /mnt/c/Users/<your Windows username>/.ssh/ ~/.ssh

That’s it! You can verify that permissions carried over with ls -al ~/.ssh/

Addendum: Set up fish in NixOS the right way

I use fish as my shell, but when I set it up in WSL I started getting errors like this:

fish: Unknown command: ls
/nix/store/lkf5vmavnxa0s37imb03gv7hs6dh5pll-fish-3.5.1/share/fish/functions/ls.fish (line 64):
    command $__fish_ls_command $__fish_ls_color_opt $opt $argv
    ^
in function 'ls'

Uh oh. Obviously, there are important directories missing from my path. It turns out that I was missing some configuration³:

{
  programs.fish.enable = true;
}

I don’t know why this issue only appeared in WSL, but fish users should probably set programs.fish.enable in NixOS whether the issue appears or not.

See also

• Nix Flakes on WSL by Xe Iaso