Flake extensions for defining vms

flake.nix

@@ -23,6 +23,11 @@
       url = "gitlab:simple-nixos-mailserver/nixos-mailserver";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    microvm = {
+      url = "github:astro/microvm.nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs = {
@@ -30,6 +35,10 @@
     nixpkgs,
     ...
   } @ inputs: let
+    lib = import ./lib {
+      inherit nixpkgs;
+      inherit self;
+    };
     system = "x86_64-linux";
     pkgs = import nixpkgs {inherit system;};
   in {
@@ -41,10 +50,12 @@
         inputs.agenix.nixosModules.default
         inputs.home-manager.nixosModules.default
         inputs.simple-nixos-mailserver.nixosModule
+        inputs.microvm.nixosModules.microvm
+        {microvm.hyprvisor = "qemu";}
       ];
     in {
       server-vm = nixpkgs.lib.nixosSystem {
-        specialArgs = {inherit inputs;};
+        specialArgs = {inherit inputs lib;};
         modules =
           [
             (import ./disko.nix {
@@ -65,7 +76,7 @@
       };
 
       server = nixpkgs.lib.nixosSystem {
-        specialArgs = {inherit inputs;};
+        specialArgs = {inherit inputs lib;};
         modules =
           [
             (import ./disko.nix {

lib/default.nix

@@ -0,0 +1,29 @@
+{
+  self,
+  nixpkgs,
+  ...
+}:
+nixpkgs.lib.extend (
+  _final: prev: let
+    inherit (prev) mkIf;
+  in {
+    extensions = {
+      createvm = {
+        name,
+        system ? nixpkgs.system,
+        config,
+      }: {microvm, ...}: {
+        imports = [microvm.host];
+        microvm.vms.${name} = {
+          pkgs = import nixpkgs {inherit system;};
+          inherit config;
+          # Host build-time reference to where the MicroVM NixOS is defined
+          # under nixosConfigurations
+          flake = self;
+          # Specify from where to let `microvm -u` update later on
+          updateFlake = "git+file:///etc/nixos";
+        };
+      };
+    };
+  }
+)