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nix module and flake for declarative non-NixOS VMs
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Git Sagar 6a62a649bd generalize: assert the static address per boot, not once during the build 
Setting it from post-oobe.cmd could never have worked, and the reason is worth
writing down. Without delayOobeRun, OOBE runs inside the build VM -- whose NIC
is qemu user networking, on a different subnet, with a different MAC. The
address was being applied to an adapter that does not exist on the real host.
Windows then meets the target's NIC as new hardware and defaults to DHCP.

RDP came through the same script unharmed because its settings are
registry-wide rather than per-adapter, which is why one worked and the other
did not despite sitting a few lines apart.

So the script is now registered as an onstart scheduled task running as SYSTEM.
It was already idempotent, and per-boot also survives the adapter being
replaced again later.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0117qMyjpuXsjpVAcpJbFD8g
2026-09-10 07:28:14 -03:00
lib generalize: assert the static address per boot, not once during the build 2026-09-10 07:28:14 -03:00
nixos pci: keep multifunction devices together; data disk: diskpart, not Storage cmdlets 2026-09-10 04:58:54 -03:00
.env-export-vmix-cli-local vmix CLI, laptop images, SDL display 2026-05-23 21:56:51 -03:00
.gitignore fist commit - images lib in a working condition for debian 2024-05-23 16:33:38 +00:00
cli.nix pass XAUTHORITY to builds for SDL display in X11 sessions 2026-05-31 04:51:53 -03:00
flake.lock vmix CLI, laptop images, SDL display 2026-05-23 21:56:51 -03:00
flake.nix fix: use vmix's own locked nixpkgs for all image building 2026-06-15 10:04:52 -03:00
README.md add README with usage, architecture, and examples 2026-06-07 10:46:32 +05:30

README.md

vmix

Composable QEMU VM image building and orchestration for NixOS.

What it does

vmix provides:

  • Image building — reproducible Linux (Debian) and Windows qcow2 images via Nix derivations
  • NixOS module — declarative VM management with QEMU in network namespaces
  • CLI tool — build, copy-to-disk, and run images from the command line

Usage

As a flake input

# flake.nix
inputs.vmix.url = "git+https://git.sagar.ch/dotfiles/vmix.nix.git";

# In your NixOS configuration (or globally via serverFunctions)
imports = [ inputs.vmix.nixosModules.default ];

# Use vmixLib via overlay
nixpkgs.overlays = [ inputs.vmix.overlays.default ];
# Then: pkgs.vmixLib.linux, pkgs.vmixLib.windows, pkgs.vmixLib.network

As a CLI

# Enter dev shell
nix develop

# Build an image
vmix build --image windows.images.win10.laptop \
  --generalize username=User,password=secret,hostname=PC

# Write to local disk
vmix copy --image windows.images.win10.laptop \
  --generalize username=User,password=secret \
  --to-disk /dev/sda

# Write to remote disk (streamed via SSH + LZ4)
vmix copy --image windows.images.win10.laptop \
  --generalize username=User,password=secret \
  --to-remote-disk root@10.10.10.100:/dev/nvme0n1

# Boot a built image with QEMU
vmix run ./result --mem 8192 --smp 8 --ahci

Flake outputs

Output Description
overlays.default Nix overlay exposing pkgs.vmixLib
nixosModules.default NixOS module for declarative VM management
lib.x86_64-linux Library functions (images + network utilities)
packages.x86_64-linux.default vmix CLI tool
apps.x86_64-linux.default Runnable vmix app

Repository structure

flake.nix          # Flake entry point
module.nix         # NixOS module export
overlay.nix        # Nix overlay (vmixLib pinned to nixpkgs 25-11)
cli.nix            # CLI tool (build, copy, run)

lib/
  default.nix      # Exports: images (linux + windows) + network
  network.nix      # IPv4/CIDR utilities
  images/
    linux/         # Debian image building + customization
    windows/       # Windows image building + customization
      helpers/     # makeImage, customizeImage, makeWinISO, etc.
      templates/   # Registry tweaks, app installers, essentials
      drivers/     # VirtIO, AMD GPU drivers
      win10/       # Windows 10 LTSC images
      win11/       # Windows 11 images

nixos/
  default.nix      # NixOS module entry point
  networks/        # Network namespace management (LAN, WAN, macvtap)
  vms/             # VM lifecycle management (QEMU, tap devices, DHCP)

Image building

Windows pipeline

  1. makeImage — unattended install from upstream ISO via QEMU
  2. customizeImageFold — apply modular templates (registry, apps, drivers)
  3. generalize — sysprep + OOBE for deployment to real hardware

Linux pipeline

  1. Fetch upstream Debian cloud image
  2. customizeImageFold — apply templates via virt-customize

Key patterns

  • customizeImageFold — builtins.foldl' over templates for composable layered images
  • _vmixOsType — all images carry "linux" or "windows" metadata for auto-detection
  • Offline registry — Windows templates use ControlSet001 for offline virt-win-reg --merge

NixOS module

Declare VMs and networks:

vmix.namespaces."lab" = {
  networks.lan1 = {
    subnet = "10.99.1.0/24";
    dhcp.enable = true;
  };
  vms.myvm = {
    image = pkgs.vmixLib.linux.images.debian.v12.upstream;
    memory = 2048;
    cores = 2;
    interfaces.lan1 = { ip = "10.99.1.10"; };
    autostart = true;
  };
};

Features:

  • Network namespaces with WAN (veth), LAN (bridge + dnsmasq), macvtap
  • ACPI graceful shutdown via QMP socket
  • 9p shares with auto-created mount targets
  • Conditional macvtap service (only created when macvtaps are configured)