cygwin: add a system builder with a working nix

.github/workflows/cygwin-bootstrap.yml

@@ -0,0 +1,31 @@
+name: Cygwin Bootstrap Release
+on:
+  push:
+    tags: 'bootstrap/*'
+
+permissions:
+  contents: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Create Release
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+        run: |
+          tag="${GITHUB_REF_NAME}"
+          gh release create --draft "$tag" --title "$tag"
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: DeterminateSystems/nix-installer-action@c5a866b6ab867e88becbed4467b93592bce69f8a
+      - uses: DeterminateSystems/magic-nix-cache-action@b4ad0b1e587499958543d6e793cd46510a21e7c2
+      - name: Build
+        run: nix build -f pkgs/top-level/release-cross.nix bootstrapTools.x86_64-pc-cygwin.unpack -o unpack.nar.xz
+      - name: Upload
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+        run: gh release upload "${GITHUB_REF_NAME}" unpack.nar.xz

.github/workflows/cygwin.yml

@@ -0,0 +1,55 @@
+name: cygwin
+
+permissions: {}
+
+on:
+  push:
+
+jobs:
+  build-tarball:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: DeterminateSystems/nix-installer-action@c5a866b6ab867e88becbed4467b93592bce69f8a
+      - uses: DeterminateSystems/magic-nix-cache-action@b4ad0b1e587499958543d6e793cd46510a21e7c2
+      - name: build tarball
+        run: nix build -f nixos/release.nix cygwinTarball.x86_64-linux
+      - uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+        with:
+          name: tarball
+          path: result
+  build-bootstrap:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+      - uses: DeterminateSystems/nix-installer-action@c5a866b6ab867e88becbed4467b93592bce69f8a
+      - uses: DeterminateSystems/magic-nix-cache-action@b4ad0b1e587499958543d6e793cd46510a21e7c2
+      - name: build bootstrap
+        run: nix build -f pkgs/top-level/release-cross.nix bootstrapTools.x86_64-pc-cygwin.unpack -o unpack.nar.xz
+      - uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+        with:
+          name: bootstrap
+          path: unpack.nar.xz
+  test:
+    runs-on: windows-latest
+    needs: build-tarball
+    steps:
+      - uses: actions/download-artifact@37930b1c2abaa49bbe596cd826c3c89aef350131 # v7.0.0
+        with:
+          name: tarball
+      - name: install
+        run: tarball/install.ps1 cygwin
+      - name: get-info
+        shell: pwsh cygwin/cygwin.ps1 {0}
+        run: nix-info
+    # - name: build
+    #   shell: pwsh cygwin/cygwin.ps1 {0}
+    #   run: nix build --no-sandbox nixpkgs#hello
+    # - uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+    #   with:
+    #     name: tarball
+    #     path: result

bootstrap.nix

@@ -0,0 +1 @@
+/nix/store/2m6hgrgdccz1yrpqlda0iz3ysxcipnj2-unpacked

check-cygwin

@@ -0,0 +1,14 @@
+#!/bin/sh
+set -eo pipefail
+echo BAD:
+nix derivation show -r .#cygwinSystem.config.system.build.tarball.stdenvDeps \
+    | jq -r 'map_values(select(.system == "x86_64-cygwin")) | keys_unsorted .[]'
+
+nix derivation show -r -f. --argstr system x86_64-cygwin nix \
+    | jq -r 'map_values(select(.system == "x86_64-linux")) | keys_unsorted .[]' \
+    | sort > target
+nix derivation show -r .#cygwinSystem.config.system.build.tarball.stdenvDeps \
+    | jq -r 'map_values(select(.system == "x86_64-linux")) | keys_unsorted .[]' \
+    | sort > bootstrap
+echo MISSING:
+comm -13 bootstrap target

cygwin-custom.nix

@@ -0,0 +1,20 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+{
+  imports = [
+    ./cygwin-system.nix
+  ];
+
+  environment.systemPackages = [ pkgs.rsync ];
+
+  nix = {
+    extraOptions = ''
+      secret-key-files = /var/store-key
+    '';
+  };
+}

cygwin-system.nix

@@ -0,0 +1,23 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+{
+  imports = [
+    ./nixos/maintainers/scripts/cygwin/system.nix
+    ./nixos/maintainers/scripts/cygwin/tarball.nix
+  ];
+
+  nix = {
+    settings.experimental-features = [
+      "nix-command"
+      "flakes"
+    ];
+  };
+
+  nixpkgs.buildPlatform = lib.mkDefault builtins.currentSystem;
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-cygwin";
+}

hydra/flake.nix

@@ -0,0 +1,49 @@
+{
+  outputs =
+    { nixpkgs, ... }:
+    {
+      nixosConfigurations.container = nixpkgs.lib.nixosSystem {
+        system = "x86_64-linux";
+        modules = [
+          {
+            boot.isNspawnContainer = true;
+
+            services.hydra = {
+              enable = true;
+              hydraURL = "http://localhost:3000";
+              notificationSender = "hydra@localhost";
+              useSubstitutes = true;
+            };
+
+            networking.firewall.allowedTCPPorts = [ 3000 ];
+            networking.useHostResolvConf = nixpkgs.lib.mkForce false;
+            networking.nameservers = [ "8.8.8.8" ];
+
+            programs.ssh.extraConfig = nixpkgs.lib.mkAfter ''
+              Host cygwin-vm
+                User Quickemu
+                HostName 10.233.1.1
+                Port = 22220
+            '';
+
+            services.openssh = {
+              knownHosts = {
+                cygwin-vm = {
+                  hostNames = [ "[10.233.1.1]:22220" ];
+                  publicKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHJGc5UkkNeYGjBLpgvdZZ8GeW8QtZsvC9IuTMNzLJ/N";
+                };
+              };
+            };
+
+            nix.distributedBuilds = true;
+            nix.buildMachines = [
+              {
+                hostName = "cygwin-vm";
+                system = "x86_64-cygwin";
+              }
+            ];
+          }
+        ];
+      };
+    };
+}

lib/systems/flake-systems.nix

@@ -25,4 +25,5 @@
   "powerpc64le-linux"
   "riscv64-linux"
   "x86_64-freebsd"
+  "x86_64-cygwin"
 ]

maintainers/scripts/bootstrap-files/refresh-tarballs.bash

@@ -99,6 +99,7 @@ CROSS_TARGETS=(
     s390x-unknown-linux-gnu
     x86_64-unknown-freebsd
     loongarch64-unknown-linux-gnu
+    x86_64-pc-cygwin
 )
 
 is_cross() {
@@ -168,6 +169,7 @@ for target in "${targets[@]}"; do
         *linux*) nixpkgs_prefix="pkgs/stdenv/linux" ;;
         *darwin*) nixpkgs_prefix="pkgs/stdenv/darwin" ;;
         *freebsd*) nixpkgs_prefix="pkgs/stdenv/freebsd" ;;
+        *cygwin*) nixpkgs_prefix="pkgs/stdenv/cygwin" ;;
         *) die "don't know where to put '$target'" ;;
     esac
 

nixos/maintainers/scripts/cygwin/profile.nix

@@ -0,0 +1,94 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+
+{
+  imports = [
+    ../../../modules/profiles/minimal.nix
+  ];
+
+  config = lib.mkIf pkgs.stdenv.hostPlatform.isCygwin {
+    boot = {
+      bcache.enable = false;
+      initrd = {
+        supportedFilesystems = [ ];
+      };
+      kernel.sysctl = lib.mkForce { };
+      loader.grub.enable = false;
+      modprobeConfig.enable = false;
+      supportedFilesystems = [ ];
+    };
+
+    console.enable = false;
+
+    fonts.fontconfig.enable = false;
+
+    # the default requires glibcLocales
+    i18n.supportedLocales = [ ];
+
+    networking = {
+      dhcpcd.enable = false;
+      firewall.enable = false;
+      resolvconf.enable = false;
+    };
+
+    programs = {
+      fuse.enable = false;
+      less.enable = lib.mkForce false;
+      nano.enable = false;
+      ssh.systemd-ssh-proxy.enable = false;
+    };
+
+    security = {
+      pam.enable = false;
+      shadow.enable = false;
+      sudo.enable = false;
+    };
+
+    services = {
+      lvm.enable = false;
+      udev.enable = false;
+    };
+
+    system = {
+      disableInstallerTools = true;
+      # this is needed because tasks/filesystems.nix unconditionally adds
+      # dosfstools, and tasks/filesystems/ext adds e2fsprogs
+      fsPackages = lib.mkForce [ ];
+      # these match the cygwin defaults when "file" is prepended
+      nssDatabases = {
+        passwd = [ "db" ];
+        group = [ "db" ];
+      };
+    };
+
+    systemd = {
+      enable = false;
+      coredump.enable = false;
+    };
+
+    users = {
+      users = lib.mkForce { };
+      groups = lib.mkForce { };
+    };
+
+    environment.corePackages =
+      with pkgs;
+      lib.mkForce [
+        bash
+        coreutils
+        openssh
+        curl
+        config.nix.package
+      ];
+    environment.defaultPackages = lib.mkForce [ ];
+
+    nix = {
+      settings.sandbox = false;
+      package = pkgs.nixVersions.git;
+    };
+  };
+}