Enable ISO ARM cross-compilation & update CI config

- Allow rune to cross compile ARM binaries

.github/workflows/build-iso.yml

@@ -17,22 +17,16 @@ jobs:
     strategy:
       matrix:
         include:
-          # x86 ISOs on x86 runners
           - iso-type: server
             arch: x86
-            runner: ubuntu-latest
-          - iso-type: desktop
-            arch: x86
-            runner: ubuntu-latest
-          # ARM ISOs on ARM runners
           - iso-type: server
             arch: arm
-            runner: ubuntu-latest-arm64
+          - iso-type: desktop
+            arch: x86
           - iso-type: desktop
             arch: arm
-            runner: ubuntu-latest-arm64
 
-    runs-on: ${{ matrix.runner }}
+    runs-on: ubuntu-latest
 
     steps:
       - name: Checkout repository
@@ -41,9 +35,22 @@ jobs:
       - name: Install Nix
         uses: DeterminateSystems/nix-installer-action@v9
 
+      - name: Setup QEMU for ARM emulation
+        if: ${{ matrix.arch == 'arm' }}
+        uses: docker/setup-qemu-action@v3
+        with:
+          platforms: arm64
+
       - name: Setup Nix cache
         uses: DeterminateSystems/magic-nix-cache-action@v2
 
+      - name: Enable ARM emulation
+        if: ${{ matrix.arch == 'arm' }}
+        run: |
+          echo "extra-platforms = aarch64-linux" >> $HOME/.config/nix/nix.conf
+          echo "extra-sandbox-paths = /run/binfmt" >> $HOME/.config/nix/nix.conf
+          sudo systemctl restart nix-daemon.service
+
       - name: Build ISO (with retry)
         uses: nick-fields/retry@v3
         with:
@@ -52,15 +59,27 @@ jobs:
           retry_wait_seconds: 30
           command: |
             cd iso
-            nix build .#${{ matrix.iso-type }}-iso-${{ matrix.arch }} \
+            if [ "${{ matrix.arch }}" = "arm" ]; then
+              nix build .#${{ matrix.iso-type }}-iso-arm \
+                --system x86_64-linux \
+                --extra-platforms aarch64-linux \
                 --print-build-logs \
                 --accept-flake-config
+            else
+              nix build .#${{ matrix.iso-type }}-iso-x86 \
+                --print-build-logs \
+                --accept-flake-config
+            fi
 
       - name: Get ISO filename
         id: iso-info
         run: |
           cd iso
-          ISO_PATH=$(nix build .#${{ matrix.iso-type }}-iso-${{ matrix.arch }} --print-out-paths --no-link)
+          if [ "${{ matrix.arch }}" = "arm" ]; then
+            ISO_PATH=$(nix build .#${{ matrix.iso-type }}-iso-arm --print-out-paths --no-link)
+          else
+            ISO_PATH=$(nix build .#${{ matrix.iso-type }}-iso-x86 --print-out-paths --no-link)
+          fi
           ISO_FILE=$(find $ISO_PATH -name "*.iso" -o -name "*.iso.zst" | head -1)
           ISO_NAME=$(basename "$ISO_FILE")
           echo "iso-path=$ISO_FILE" >> $GITHUB_OUTPUT
@@ -99,7 +118,7 @@ jobs:
             - **Server ISOs**: Minimal server environment with SSH access
             - **Desktop ISOs**: GNOME desktop environment for installation
             - **x86**: Intel/AMD 64-bit systems
-            - **ARM**: ARM64 systems
+            - **ARM**: ARM64 systems (cross-compiled)
 
             ### Usage:
             1. Download the appropriate ISO for your system

hosts/x86/rune/hardware.nix

@@ -48,6 +48,9 @@
       "amdgpu"
     ];
     extraModulePackages = [ ];
+
+    # Allow running ARM binaries on x86_64; for Cross Compilation
+    binfmt.emulatedSystems = [ "aarch64-linux" ];
   };
 
   # For less permission issues with SSHFS

iso/default.nix

@@ -7,15 +7,17 @@
   system,
   ...
 }:
+let
+  isCross = pkgs.stdenv.buildPlatform.system != pkgs.stdenv.hostPlatform.system;
+in
 {
-  ## ISO ##
   isoImage = {
     isoName = lib.mkForce "nixos-${config.hostSpec.hostName}-${config.system.nixos.label}-${pkgs.stdenv.hostPlatform.system}.iso";
     makeEfiBootable = true;
     makeUsbBootable = true;
     compressImage = false;
     squashfsCompression = lib.mkIf isARM "gzip";
-    includeSystemBuildDependencies = lib.mkIf isARM false;
+    includeSystemBuildDependencies = lib.mkIf (isARM || isCross) false;
   };
 
   ## SSH  & NETWORK ##
@@ -56,7 +58,6 @@
   system.stateVersion = "25.05";
   nixpkgs.hostPlatform = system;
   users.mutableUsers = lib.mkForce true; # Allow password changes
-  boot.kernelPackages = pkgs.linuxPackages_latest;
 
   nixpkgs.config = {
     allowUnsupportedSystem = true;

iso/flake.nix

@@ -87,7 +87,7 @@
           }) configs
         );
 
-      # Generate packages per system - each system only exposes its own packages
+      # Generate packages per system - all available on x86_64 via cross-compilation
       mkPackages =
         system:
         let
@@ -103,13 +103,11 @@
     {
       nixosConfigurations = mkConfigurations;
 
-      # Each system only exposes packages it can build
       packages = {
-        "${X86}" = mkPackages X86;
+        "${X86}" = (mkPackages X86) // (mkPackages ARM);
         "${ARM}" = mkPackages ARM;
       };
 
-      # For convenience - all systems get all configs
       inherit (dot-nix.outputs) overlays;
     };
 }