fix: auto-installer works fully offline

installer/auto-install.nix

@@ -1,7 +1,6 @@
 # This module defines a systemd service that automatically installs NixOS to the disk.
 # It is intended to be used in an installation ISO.
-# It expects `targetSystem` (the closure to install), `diskoScript` (the partitioning script),
-# and `closureExport` (the pre-built NAR archive) to be passed as arguments.
+# It expects `targetSystem` (the closure to install) and `diskoScript` (the partitioning script) to be passed as arguments.
 {
   config,
   lib,
@@ -9,34 +8,26 @@
   inputs,
   hostName,
   hostPlatform,
-  targetSystem,
+  targetSystemBuild,
   diskoScript,
-  closureExport,
   ...
 }:
 {
-  # Ensure the entire system closure and all dependencies are included in the ISO
   environment.systemPackages = [
     pkgs.git
     pkgs.bashInteractive
     pkgs.curl
-    targetSystem
-  ];
-
-  # Explicitly include the pre-built closure export and system in the ISO image
-  isoImage.contents = [
-    {
-      source = closureExport;
-      target = "/closure-export";
-    }
-    {
-      source = targetSystem;
-      target = "/system";
-    }
+    targetSystemBuild.toplevel
   ];
 
   nixpkgs.hostPlatform = hostPlatform;
 
+  nix.settings.experimental-features = "nix-command flakes";
+
+  system.extraDependencies = with targetSystemBuild; [ toplevel etc bootStage2 ];
+
+  isoImage.storeContents = [ targetSystemBuild.toplevel ];
+
   systemd.services.auto-install = {
     description = "Automatic NixOS install for ${hostName}";
     after = [
@@ -59,17 +50,12 @@
       echo ">>> Running disko script..."
       ${diskoScript}
 
-      echo ">>> Importing pre-built closure into target store..."
-      # Import the closure that was exported at build time
-      ${pkgs.nix}/bin/nix-store --store /mnt --import < /closure-export/closure.nar > /dev/null
-
-      echo ">>> Running nixos-install..."
-      # Install with pre-built closure already imported (no evaluation or fetching needed)
-      ${pkgs.nix}/bin/nixos-install \
-        --no-root-passwd \
-        --root /mnt \
-        --system ${targetSystem} \
-        --option substitute false
+      echo ">>> Setting up NixOS..."
+      nixos-install \
+      --system ${targetSystemBuild.toplevel} \
+      --no-root-passwd \
+      --no-channel-copy \
+      --substituters "" 
 
       echo ">>> Done. Rebooting."
       systemctl reboot