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A Nix Flake to build NixOS and run it on one of several Type-2 Hypervisors on NixOS/Linux or macOS. The project is intended to provide a more isolated alternative to nixos-container. You can either build and run MicroVMs like Nix packages, or alternatively install them as systemd services declaratively in your host's Nix Flake or imperatively with the provided microvm command.

Project Presentation (video)

• MicroVMs are Virtual Machines but use special device interfaces (virtio) for high performance.
• This project runs them on NixOS/Linux hosts and macOS (via vfkit).
• You can choose from eight hypervisors for each MicroVM.
• MicroVMs have a fixed RAM allocation (default: 512 MB) but can be shrunk using microvm-balloon
• MicroVMs have a read-only root disk with either a prepopulated /nix/store or by mounting the host's along with an optional writable overlay. This filesystem can be built as either squashfs (smaller) or erofs (faster).
• You define your MicroVMs in a Nix Flake's nixosConfigurations section, reusing the nixosModules that are exported by this Flake.
• MicroVMs can access stateful filesystems either on a image volume as a block device, or alternatively as a shared directory hierarchy through 9p or virtiofs.
• Zero, one, or more virtual tap ethernet network interfaces can be attached to a MicroVM. qemu, kvmtool, and vfkit also support user networking which requires no additional setup on the host.

nix registry add microvm github:microvm-nix/microvm.nix

(If you do not want to inflict this change on your system, just replace microvm with github:microvm-nix/microvm.nix in the following examples.)

nix flake init -t microvm
$EDITOR flake.nix
nix run .#my-microvm

nix run microvm#qemu-example
nix run microvm#firecracker-example
nix run microvm#cloud-hypervisor-example
nix run microvm#crosvm-example
nix run microvm#kvmtool-example
nix run microvm#stratovirt-example
# On macOS only:
nix run microvm#vfkit-example

nix run microvm#vm

Check networkctl status virbr0 for the DHCP leases of the nested MicroVMs. They listen for ssh with an empty root password.

On Linux with cloud-hypervisor and Wayland forwarding:

nix run microvm#graphics neverball

On macOS with vfkit, enable graphics with microvm.graphics.enable = true.

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