init

.gitignore

@@ -0,0 +1,2 @@
+*.img
+*.qcow2

configuration.nix

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+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  indexHtml = pkgs.writeText "index.html" ''
+    hello mofo
+  '';
+in
+{
+  imports = [
+    ./microvm.nix
+    ./vm-variant.nix
+  ];
+  networking = {
+    firewall.enable = false;
+    useDHCP = lib.mkForce true;
+    hostName = "demo";
+  };
+  services.avahi = {
+    enable = true;
+    nssmdns = true;
+    publish = {
+      enable = true;
+      addresses = true;
+      workstation = true;
+    };
+  };
+  # boot = {
+  #   # loader.grub.device = "nodev";
+  #   kernelParams = [ "console=ttyS0" ];
+  # };
+
+  users.users = {
+    root = {
+      password = "";
+    };
+  };
+
+  # Optional: Make sure DNS is configured
+  networking = {
+    nameservers = [
+      "9.9.9.9"
+    ];
+    # Enable networking
+    # networkmanager.enable = true;
+  };
+  nix = {
+    settings.experimental-features = [
+      "nix-command"
+      "flakes"
+    ];
+  };
+  services.nginx = {
+    enable = true;
+    virtualHosts."localhost" = {
+      root = "${pkgs.runCommand "nginx-root" { } ''
+        mkdir -p $out
+        cp ${indexHtml} $out/index.html
+      ''}";
+      locations."/" = {
+        index = "index.html";
+      };
+    };
+  };
+
+  # users.mutableUsers = false;
+  system.stateVersion = "25.05";
+}

flake.lock

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+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "microvm": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "spectrum": "spectrum"
+      },
+      "locked": {
+        "lastModified": 1752095991,
+        "narHash": "sha256-+paXzPg6SN3O+YKtQKiU+kQE1EkfsrI1XEYTxI4DSFk=",
+        "owner": "astro",
+        "repo": "microvm.nix",
+        "rev": "f30b1412b73df264dc9cac154d340645add350ff",
+        "type": "github"
+      },
+      "original": {
+        "owner": "astro",
+        "repo": "microvm.nix",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1751943650,
+        "narHash": "sha256-7orTnNqkGGru8Je6Un6mq1T8YVVU/O5kyW4+f9C1mZQ=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "88983d4b665fb491861005137ce2b11a9f89f203",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-25.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "microvm": "microvm",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "spectrum": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1751265943,
+        "narHash": "sha256-XoHSo6GEElzRUOYAEg/jlh5c8TDsyDESFIux3nU/NMc=",
+        "ref": "refs/heads/main",
+        "rev": "37c8663fab86fdb202fece339ef7ac7177ffc201",
+        "revCount": 904,
+        "type": "git",
+        "url": "https://spectrum-os.org/git/spectrum"
+      },
+      "original": {
+        "type": "git",
+        "url": "https://spectrum-os.org/git/spectrum"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-25.05";
+    microvm = {
+      url = "github:astro/microvm.nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+  outputs =
+    {
+      microvm,
+      nixpkgs,
+      ...
+    }:
+    let
+      system = "x86_64-linux";
+      pkgs = import nixpkgs { inherit system; };
+      lib = nixpkgs.lib;
+      run-vm = pkgs.writeShellApplication {
+        name = "nix-vm";
+        runtimeInputs = with pkgs; [
+          jq
+          gum
+        ];
+        text = builtins.readFile ./scripts/run-vm.sh;
+      };
+    in
+    {
+      nixosConfigurations.demo = nixpkgs.lib.nixosSystem {
+        system = "x86_64-linux";
+        modules = [
+          microvm.nixosModules.microvm
+          ./configuration.nix
+        ];
+      };
+      apps.x86_64-linux.run-vm = {
+        type = "app";
+        program = "${lib.getExe run-vm}";
+      };
+    };
+}

microvm.nix

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+_: {
+
+  microvm = {
+    interfaces = [
+      {
+        type = "user";
+
+        # interface name on the host
+        id = "vm-a1";
+
+        # Ethernet address of the MicroVM's interface, not the host's
+        #
+        # Locally administered have one of 2/6/A/E in the second nibble.
+        mac = "02:00:00:00:00:01";
+      }
+    ];
+    volumes = [
+      {
+        mountPoint = "/var";
+        image = "var.img";
+        size = 256;
+      }
+    ];
+    shares = [
+      {
+        # use proto = "virtiofs" for MicroVMs that are started by systemd
+        proto = "9p";
+        tag = "ro-store";
+        # a host's /nix/store will be picked up so that no
+        # squashfs/erofs will be built for it.
+        source = "/nix/store";
+        mountPoint = "/nix/.ro-store";
+      }
+    ];
+
+    # "qemu" has 9p built-in!
+    hypervisor = "qemu";
+    socket = "control.socket";
+  };
+}

scripts/run-vm.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+if ! command -v gum &> /dev/null; then
+  echo "gum (from charm.sh) is required but not found in PATH."
+  exit 1
+fi
+
+if ! command -v jq &> /dev/null; then
+  echo "jq is required but not found in PATH."
+  exit 1
+fi
+
+# List flake configs without evaluating them
+HOSTS=()
+while IFS= read -r line; do
+  HOSTS+=("$line")
+done < <(nix flake show --json | jq -r '.nixosConfigurations | keys[]')
+
+if [ ${#HOSTS[@]} -eq 0 ]; then
+  echo "No NixOS configurations found in flake."
+  exit 1
+fi
+
+# Prompt user for a config
+SELECTED=$(printf "%s\n" "${HOSTS[@]}" | gum choose --header="Select a NixOS VM config:")
+
+if [ -z "$SELECTED" ]; then
+  echo "No hostname selected. Exiting."
+  exit 1
+fi
+
+echo "Building VM for flake config: $SELECTED"
+
+# Build the VM
+nix run ".#nixosConfigurations.$SELECTED.config.system.build.vm"
+
+

vm-variant.nix

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+_: {
+
+  virtualisation.vmVariant = {
+    # virtualisation.diskImage = null;
+    # Boot with tmpfs as root
+
+    fileSystems."/" = {
+      fsType = "tmpfs";
+      options = [
+        "defaults"
+        "size=1024M"
+      ];
+    };
+    virtualisation = {
+
+      forwardPorts = [
+        {
+          from = "host";
+          host.port = 8888;
+          guest.port = 80;
+        }
+      ];
+      graphics = false; # disables graphical output
+      memorySize = 1024;
+    };
+    users.users = {
+      root = {
+        password = "";
+      };
+    };
+  };
+}