Got my NixOS flake to run under WSL!

2025-09-08 05:54:03 +05:30 · 2023-08-20 17:55:05 -05:00 · 2023-08-20 17:55:05 -05:00 · 0a71232a56
commit 0a71232a56
parent e877fd63bc
18 changed files with 1063 additions and 10 deletions
--- a/profiles/wsl/nixos-wsl/modules/build-tarball.nix
+++ b/profiles/wsl/nixos-wsl/modules/build-tarball.nix
@ -0,0 +1,97 @@
+{ config, pkgs, lib, ... }:
+with builtins; with lib;
+let
+  pkgs2storeContents = l: map (x: { object = x; symlink = "none"; }) l;
+
+  nixpkgs = lib.cleanSource pkgs.path;
+
+  channelSources = pkgs.runCommand "nixos-${config.system.nixos.version}"
+    { preferLocalBuild = true; }
+    ''
+      mkdir -p $out
+      cp -prd ${nixpkgs.outPath} $out/nixos
+      chmod -R u+w $out/nixos
+      if [ ! -e $out/nixos/nixpkgs ]; then
+        ln -s . $out/nixos/nixpkgs
+      fi
+      echo -n ${toString config.system.nixos.revision} > $out/nixos/.git-revision
+      echo -n ${toString config.system.nixos.versionSuffix} > $out/nixos/.version-suffix
+      echo ${toString config.system.nixos.versionSuffix} | sed -e s/pre// > $out/nixos/svn-revision
+    '';
+
+  preparer = pkgs.writeShellScriptBin "wsl-prepare" ''
+    set -e
+
+    mkdir -m 0755 ./bin ./etc
+    mkdir -m 1777 ./tmp
+
+    # WSL requires a /bin/sh - only temporary, NixOS's activate will overwrite
+    ln -s ${config.users.users.root.shell} ./bin/sh
+
+    # WSL also requires a /bin/mount, otherwise the host fs isn't accessible
+    ln -s /nix/var/nix/profiles/system/sw/bin/mount ./bin/mount
+
+    # Set system profile
+    system=${config.system.build.toplevel}
+    ./$system/sw/bin/nix-store --store `pwd` --load-db < ./nix-path-registration
+    rm ./nix-path-registration
+    ./$system/sw/bin/nix-env --store `pwd` -p ./nix/var/nix/profiles/system --set $system
+
+    # Set channel
+    mkdir -p ./nix/var/nix/profiles/per-user/root
+    ./$system/sw/bin/nix-env --store `pwd` -p ./nix/var/nix/profiles/per-user/root/channels --set ${channelSources}
+    mkdir -m 0700 -p ./root/.nix-defexpr
+    ln -s /nix/var/nix/profiles/per-user/root/channels ./root/.nix-defexpr/channels
+
+    # It's now a NixOS!
+    touch ./etc/NIXOS
+
+    # Write wsl.conf so that it is present when NixOS is started for the first time
+    cp ${config.environment.etc."wsl.conf".source} ./etc/wsl.conf
+
+    ${lib.optionalString config.wsl.tarball.includeConfig ''
+      # Copy the system configuration
+      mkdir -p ./etc/nixos/nixos-wsl
+      cp -R ${lib.cleanSource ../.}/. ./etc/nixos/nixos-wsl
+      mv ./etc/nixos/nixos-wsl/configuration.nix ./etc/nixos/configuration.nix
+      # Patch the import path to avoid having a flake.nix in /etc/nixos
+      sed -i 's|import \./default\.nix|import \./nixos-wsl|' ./etc/nixos/configuration.nix
+    ''}
+  '';
+
+in
+{
+
+  options.wsl.tarball = {
+    includeConfig = mkOption {
+      type = types.bool;
+      default = true;
+      description = "Whether or not to copy the system configuration into the tarball";
+    };
+  };
+
+
+  config = mkIf config.wsl.enable {
+    # These options make no sense without the wsl-distro module anyway
+
+    system.build.tarball = pkgs.callPackage "${nixpkgs}/nixos/lib/make-system-tarball.nix" {
+      # No contents, structure will be added by prepare script
+      contents = [ ];
+
+      fileName = "nixos-wsl-${pkgs.hostPlatform.system}";
+
+      storeContents = pkgs2storeContents [
+        config.system.build.toplevel
+        channelSources
+        preparer
+      ];
+
+      extraCommands = "${preparer}/bin/wsl-prepare";
+
+      # Use gzip
+      compressCommand = "gzip";
+      compressionExtension = ".gz";
+    };
+
+  };
+}