pkgs.writeErofsLayers,profiles/ch-runner: MVE

$ nix-build -A examples.dummy.config.debug.closure.erofs.list | xargs
cat | xargs du -h
749M    /nix/store/bzfv5x6lycq6hzhjv6d6vlk1q8fdg9di-base0.erofs
24M     /nix/store/hp41jfq36y0mmjrzqilyh3jfsvqic3kb-nixos.erofs

$ nix run -f . examples.dummy.config.uvms.cloud-hypervisor.runner
...
<<< Welcome to NixOS 25.11pre-git (x86_64) - ttyS0 >>>

nixos login:

The definition of the `pkgs` fixpoint was moved to pkgs/default.nix.
For that, dirToAttrs was moved to lib/, imported ad hoc

profiles/uvms-guest.nix

@@ -1,47 +1,42 @@
 {
   options,
+  config,
   lib,
   pkgs,
   ...
 }:
+let
+  mkIfGuest = import ../lib/mkIfMicrovmGuest.nix { inherit options config lib; };
+in
 {
   imports = [
     ./vsock-connect-guest.nix
     ./uvms-users.nix
   ];
-  config = lib.optionalAttrs (options ? microvm) {
-    microvm = {
-      hypervisor = "cloud-hypervisor";
-      volumes = [
+  config = lib.mkMerge [
+    (mkIfGuest {
+      microvm = {
+        hypervisor = "cloud-hypervisor";
+        volumes = [
+          {
+            image = "swapfile.img";
+            mountPoint = "/var/swapfiles";
+            size = 1024;
+          }
+        ];
+      };
+      swapDevices = [
         {
-          image = "swapfile.img";
-          mountPoint = "/var/swapfiles";
-          size = 1024;
+          device = "/var/swapfiles/swap0";
+          size = 768;
         }
       ];
-      cloud-hypervisor.extraArgs = [
-        "--api-socket=ch.sock"
-      ];
-    };
-    swapDevices = [
-      {
-        device = "/var/swapfiles/swap0";
-        size = 768;
-      }
-    ];
+    })
+    {
 
-    boot.kernelParams = [ "zswap.enabled=1" ];
-    zramSwap.enable = false;
+      boot.kernelParams = [ "zswap.enabled=1" ];
+      zramSwap.enable = false;
 
-    systemd.services."microvm@".serviceConfig.ExecStartPost =
-      pkgs.writeShellScript "microvm-fix-umask" ''
-        if [[ -e CONNECT.vsock ]] ; then
-          chmod g+r CONNECT.vsock
-        fi
-      '';
-
-    systemd.tmpfiles.settings."10-muvm" = {
-      "/var/lib/microvms/*/CONNECT.sock".z.mode = "660";
-    };
-  };
+    }
+  ];
 }