MicroVM.nix

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A Nix Flake to build NixOS and run it on one of several Type-2 Hypervisors on NixOS/Linux. 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.

(de) Projektvorstellung

Attention: This is a Nix Flakes-only project.

At a glance

• MicroVMs are Virtual Machines but use special device interfaces (virtio) for high performance.
• This project runs them on NixOS hosts.
• You can choose one of five 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 and kvmtool also support user networking which requires no additional setup on the host.

Hypervisors

Hypervisor	Language	Restrictions
qemu	C
cloud-hypervisor	Rust	no 9p shares
firecracker	Rust	no 9p/virtiofs shares
crosvm	Rust	no control socket
kvmtool	C	no virtiofs shares, no control socket

Installation

nix registry add microvm github:astro/microvm.nix

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

Start writing your own NixOS MicroVM definitions

nix flake init -t microvm

Examples

Run MicroVMs on your local machine

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

Run a MicroVM example with nested MicroVMs on 5 different Hypervisors

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.

Commercial support

The author can implement additional features. Re-use our experience in building infrastructure with these techologies!

If the project is already working fine for you, I will be very happy if you pressed the 💗sponsor button. This income allows me to spend more time maintaining my open-source projects.