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.
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 -ior for flakes users like this:
nix profile install github:nix-community/nixos-generatorsor run from the nix flake without installing:
nix run github:nix-community/nixos-generators -- --help
| format | description |
|---|---|
| amazon | Amazon EC2 image |
| azure | Microsoft azure image (Generation 1 / VHD) |
| cloudstack | qcow2 image for cloudstack |
| do | Digital Ocean image |
| docker | Docker image (uses systemd to run, probably only works in podman) |
| gce | Google Compute image |
| hyperv | Hyper-V Image (Generation 2 / VHDX) |
| install-iso | Installer ISO |
| install-iso-hyperv | Installer ISO with enabled hyper-v support |
| iso | ISO |
| kexec | kexec tarball (extract to / and run /kexec_nixos) |
| kexec-bundle | same as before, but it's just an executable |
| kubevirt | KubeVirt image |
| linode | Linode image |
| lxc | create a tarball which is importable as an lxc container, use together with lxc-metadata |
| lxc-metadata | the necessary metadata for the lxc image to start, usage: lxc image import $(nixos-generate -f lxc-metadata) $(nixos-generate -f lxc) |
| openstack | qcow2 image for openstack |
| proxmox | VMA file for proxmox |
| proxmox-lxc | LXC template for proxmox |
| qcow | qcow2 image |
| qcow-efi | qcow2 image with efi support |
| raw | raw image with bios/mbr. for physical hardware, see the 'raw and raw-efi' section |
| raw-efi | raw image with efi support. for physical hardware, see the 'raw and raw-efi' section |
| sd-aarch64 | Like sd-aarch64-installer, but does not use default installer image config. |
| sd-aarch64-installer | create an installer sd card for aarch64. For cross compiling use --system aarch64-linux and read the cross-compile section. |
| vagrant-virtualbox | VirtualBox image for Vagrant |
| virtualbox | virtualbox VM |
| vm | only used as a qemu-kvm runner |
| vm-bootloader | same as vm, but uses a real bootloader instead of netbooting |
| vm-nogui | same as vm, but without a GUI |
| vmware | VMWare image (VMDK) |
Run nixos-generate --help for detailed usage information.
Adds ability to select a specific channel version.
Example:
nix-shell --command './nixos-generate -f iso -I nixpkgs=channel:nixos-19.09'
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
To specify the size of the generated disk image, use the --disk-size argument,
specifying the size in megabytes. This is currently supported by the following
formats. If this argument is unspecified it defaults to automatic sizing based
on the generated NixOS build.
- hyperv
- proxmox
- qcow
- raw-efi
- raw
- vm
- vm-nogui
- vmware
Example (20GB disk):
nixos-generate -c <your_config.nix> -f <format> --disk-size 20480To set the disk size in flake.nix, set diskSize in the specialArgs argument of the nixosGenerate function.
{
inputs = {
nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
nixos-generators = {
url = "github:nix-community/nixos-generators";
inputs.nixpkgs.follows = "nixpkgs";
};
xc = {
url = "github:joerdav/xc";
inputs.nixpkgs.follows = "nixpkgs";
};
};
outputs = { nixpkgs, nixos-generators, xc, ... }:
let
pkgsForSystem = system: import nixpkgs {
inherit system;
overlays = [
(final: prev: { xc = xc.packages.${system}.xc; })
];
};
allVMs = [ "x86_64-linux" "aarch64-linux" ];
forAllVMs = f: nixpkgs.lib.genAttrs allVMs (system: f {
inherit system;
pkgs = pkgsForSystem system;
});
in
{
packages = forAllVMs ({ system, pkgs }: {
vm = nixos-generators.nixosGenerate {
system = system;
specialArgs = {
pkgs = pkgs;
diskSize = 20 * 1024;
};
modules = [
# Pin nixpkgs to the flake input, so that the packages installed
# come from the flake inputs.nixpkgs.url.
({ ... }: { nix.registry.nixpkgs.flake = nixpkgs; })
# Apply the rest of the config.
./configuration.nix
];
format = "raw";
};
});
};
}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=${qemu-arm-static}/bin/qemu-arm-static" ];
}For more details on configuring binfmt, have a look at:
binfmt options,
binfmt.nix,
this comment and
clevers qemu-user.
Once you've run nixos-rebuild with these options,
you can use the --system option to create images for other architectures.
nixos-generators can be included as a NixOS module into your existing configuration.nix making all available formats available through config.formats and configurable through config.formatConfigs. New formats can be defined by adding a new entry like config.formatConfigs.my-new-format = {config, ...}: {}.
An example flake.nix demonstrating this approach is below.
Images can be built from that flake by running:
nix build .#nixosConfigurations.my-machine.config.formats.vmwareornix build .#nixosConfigurations.my-machine.config.formats.my-custom-formatornix build .#nixosConfigurations.my-machine.config.formats.<any-other-format>
{
inputs = {
nixpkgs.url = "nixpkgs/nixos-unstable";
nixos-generators = {
url = "github:nix-community/nixos-generators";
inputs.nixpkgs.follows = "nixpkgs";
};
};
outputs = { self, nixpkgs, nixos-generators, ... }: {
# A single nixos config outputting multiple formats.
# Alternatively put this in a configuration.nix.
nixosModules.my-machine = { config, ... }: {
imports = [
nixos-generators.nixosModules.all-formats
];
nixpkgs.hostPlatform = "x86_64-linux";
# customize an existing format
formatConfigs.vmware = { config, ... }: {
services.openssh.enable = true;
};
# define a new format
formatConfigs.my-custom-format = { config, modulesPath, ... }: {
imports = [ "${toString modulesPath}/installer/cd-dvd/installation-cd-base.nix" ];
formatAttr = "isoImage";
fileExtension = ".iso";
networking.wireless.networks = {
# ...
};
};
# the evaluated machine
nixosConfigurations.my-machine = nixpkgs.lib.nixosSystem {
modules = [ self.nixosModules.my-machine ];
};
};
};
}nixos-generators can be included as a Flake input and provides
a nixosGenerate 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
Custom formats can be defined by building a format module (see the
formats directory for examples) and passing it to nixosGenerate
via an the customFormats argument. customFormats should be in the form of
an attribute sets of the form <format name> = <format module> and can define
multiple custom formats. nixosGenerate will then match against these custom formats as well as the built in ones.
{
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";
# optional arguments:
# explicit nixpkgs and lib:
# pkgs = nixpkgs.legacyPackages.x86_64-linux;
# lib = nixpkgs.legacyPackages.x86_64-linux.lib;
# additional arguments to pass to modules:
# specialArgs = { myExtraArg = "foobar"; };
# you can also define your own custom formats
# customFormats = { "myFormat" = <myFormatModule>; ... };
# format = "myFormat";
};
vbox = nixos-generators.nixosGenerate {
system = "x86_64-linux";
format = "virtualbox";
};
};
};
}raw and raw-efi images can be used on physical hardware, but benefit from some tweaks.
- These images are configured to log to the serial console, and not to your display. One workaround for this is to add
boot.kernelParams = [ "console=tty0" ];to your configuration, which will override the image's defaultconsole=ttyS0. - By default, grub will timeout after 1 second. To extend this, set
boot.loader.timeout = 5;(or longer) - If boot fails for some reason, you will not get a recovery shell unless the root user is enabled, which you can do by setting a password for them (
users.users.root.password = "something";, possiblyusers.mutableUsers = true;so you can interactively change the passwords after boot) - After booting, if you intend to use
nixos-switch, consider usingnixos-generate-config.
This project is licensed under the MIT License.
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).
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