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nixos-generators

nixos-generators - one config, multiple formats

README.md

nixos-generators - one config, multiple formats

The nixos-generators project allows to take the same NixOS configuration, and generate outputs for different target formats.

Just put your stuff into the configuration.nix and then call one of the image builders.

for example:

nixos-generate -f iso

or

nixos-generate -f iso -c /etc/nixos/configuration.nix

it echoes the path to a iso image, which you then can flash onto an usb-stick or mount & boot in a virtual machine.

Installation

nixos-generators is part of nixpkgs and can be installed from there.

nixos-generators can be also installed from source into the user profile like this:

nix-env -f https://github.com/nix-community/nixos-generators/archive/master.tar.gz -i

or for flakes users like this:

nix profile install github:nix-community/nixos-generators

or run from the nix flake without installing:

nix run github:nix-community/nixos-generators -- --help

Supported formats

formatdescription
amazonAmazon EC2 image
azureMicrosoft azure image (Generation 1 / VHD)
cloudstackqcow2 image for cloudstack
doDigital Ocean image
dockerDocker image (uses systemd to run, probably only works in podman)
gceGoogle Compute image
hypervHyper-V Image (Generation 2 / VHDX)
install-isoInstaller ISO
install-iso-hypervInstaller ISO with enabled hyper-v support
isoISO
kexeckexec tarball (extract to / and run /kexec_nixos)
kexec-bundlesame as before, but it's just an executable
kubevirtKubeVirt image
linodeLinode image
lxccreate a tarball which is importable as an lxc container, use together with lxc-metadata
lxc-metadatathe necessary metadata for the lxc image to start, usage: lxc image import $(nixos-generate -f lxc-metadata) $(nixos-generate -f lxc)
openstackqcow2 image for openstack
proxmoxVMA file for proxmox
proxmox-lxcLXC template for proxmox
qcowqcow2 image
rawraw image with bios/mbr
raw-efiraw image with efi support
sd-aarch64Like sd-aarch64-installer, but does not use default installer image config.
sd-aarch64-installercreate an installer sd card for aarch64. For cross compiling use --system aarch64-linux and read the cross-compile section.
vagrant-virtualboxVirtualBox image for Vagrant
virtualboxvirtualbox VM
vmonly used as a qemu-kvm runner
vm-bootloadersame as vm, but uses a real bootloader instead of netbooting
vm-noguisame as vm, but without a GUI
vmwareVMWare image (VMDK)

Usage

Run nixos-generate --help for detailed usage information.

select a specific nixpkgs channel

adds ability to select a specific channel version.

example:

nix-shell --command './nixos-generate -f iso -I nixpkgs=channel:nixos-19.09'

Using a particular nixpkgs

To use features found in a different nixpkgs (for instance the Digital Ocean image was recently merged in nixpkgs):

NIX_PATH=nixpkgs=../nixpkgs nixos-generate -f do

Cross Compiling

To cross compile nixos images for other architectures you have to configure boot.binfmt.emulatedSystems or boot.binfmt.registrations on your host system.

In your system configuration.nix:

{
  # Enable binfmt emulation of aarch64-linux.
  boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
}

Alternatively, if you want to target other architectures:

# Define qemu-arm-static source.
let qemu-arm-static = pkgs.stdenv.mkDerivation {
  name = "qemu-arm-static";
  src = builtins.fetchurl {
    url = "https://github.com/multiarch/qemu-user-static/releases/download/v6.1.0-8/qemu-arm-static";
    sha256 = "06344d77d4f08b3e1b26ff440cb115179c63ca8047afb978602d7922a51231e3";
  };
  dontUnpack = true;
  installPhase = "install -D -m 0755 $src $out/bin/qemu-arm-static";
};
in {
  # Enable binfmt emulation of extra binary formats (armv7l-linux, for exmaple).
  boot.binfmt.registrations.arm = {
    interpreter = "${qemu-arm-static}/bin/qemu-arm-static";
    magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00'';
    mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\x00\xff\xfe\xff\xff\xff'';
  };

  # Define additional settings for nix.
  nix.extraOptions = ''
    extra-platforms = armv7l-linux
  '';
  nix.sandboxPaths = [ "/run/binfmt/arm=${qemu-arm-static}/bin/qemu-arm-static" ];
}

For more details on configuring binfmt, have a look at: binfmt options, binfmt.nix, this comment and clevers qemu-user.

Once you've run nixos-rebuild with these options, you can use the --system option to create images for other architectures.

Using in a Flake

nixos-generators can be included as a Flake input and provides a nixos-generate function for building images as Flake outputs. This approach pins all dependencies and allows for conveniently defining multiple output types based on one config.

An example flake.nix demonstrating this approach is below. vmware or virtualbox images can be built from the same configuration.nix by running nix build .#vmware or nix build .#virtualbox

{
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-unstable";
    nixos-generators = {
      url = "github:nix-community/nixos-generators";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };
  outputs = { self, nixpkgs, nixos-generators, ... }: {
    packages.x86_64-linux = {
      vmware = nixos-generators.nixosGenerate {
        system = "x86_64-linux";
        modules = [
          # you can include your own nixos configuration here, i.e.
          # ./configuration.nix
        ];
        format = "vmware";
      };
      vbox = nixos-generators.nixosGenerate {
        system = "x86_64-linux";
        format = "virtualbox";
      };
    };
  };
}

License

This project is licensed under the MIT License.

FAQ

No space left on device

this means either /tmp, /run/user/$UID or your TMPFS runs full. sometimes setting TMPDIR to some other location can help, sometimes /tmp needs to be on a bigger partition (not a tmpfs).