NixOS Generators: Azure & QEMU

Using nixos-generators to build images for Azure VM and QEMU

nixos-generators is a tool to build NixOS images for various platforms, including Azure and QEMU. This guide covers how to generate images for both.

Prerequisites

  • Nix installed with flakes enabled

  • nixos-generators installed (as a flake or via nix run)

General Usage

You can use nixos-generators as a flake or with nix run:

nix run github:nix-community/nixos-generators -- --format <format> [options]

Or with flakes:

nix build github:nix-community/nixos-generators#nixos-generate -- --format <format> [options]

1. Generate a NixOS Image for Azure VM

Azure uses the VHD format. You can generate a VHD image as follows:

nix run github:nix-community/nixos-generators -- --format azure -c /etc/nixos/configuration.nix

  • The output will be a .vhd file, which you can upload to Azure as a managed disk or custom image.

  • You can specify a custom configuration with -c or use the default.

Uploading the VHD to Azure

# Upload to Azure Storage
az storage blob upload \
  --account-name <storage-account> \
  --container-name <container> \
  --name nixos-custom.vhd \
  --file ./result/nixos.vhd \
  --type page

# Create a managed disk from the VHD
az disk create \
  --resource-group <resource-group> \
  --name nixos-disk \
  --source https://<storage-account>.blob.core.windows.net/<container>/nixos-custom.vhd

# Create a VM from the managed disk
az vm create \
  --resource-group <resource-group> \
  --name nixos-vm \
  --attach-os-disk nixos-disk \
  --os-type linux

2. Generate a NixOS Image for QEMU

QEMU uses the qcow2 format. To generate a QEMU image:

nix run github:nix-community/nixos-generators -- --format qcow2 -c /etc/nixos/configuration.nix

  • The output will be a .qcow2 file, which you can use directly with QEMU or other virtualization tools.

Running the Image with QEMU

qemu-system-x86_64 -m 2048 -drive file=./result/nixos.qcow2,format=qcow2 -nographic

Customizing the Configuration

You can pass a custom NixOS configuration file with the -c flag. For example:

nix run github:nix-community/nixos-generators -- --format azure -c ./my-azure-config.nix

References

PreviousFlakes: The Future of NixNextWSL2

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