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.

Warning: This is a Nix Flakes-only project. Use with nix-shell -p nixFlakes

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)
• 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
• 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 as a shared directory hierarchy through 9p or virtiofs.
• Zero, one, or more virtual tap ethernet network interfaces can be attached to a MicroVM.

Hypervisors

While ubiquitous qemu seems to work in most situations, other hypervisors tend to break with Linux kernel updates. Especially crosvm and kvmtool need a lot of luck to get going.

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 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 MicroVMs. They listen for ssh with an empty root password.

Commercial support

The author can be hired to implement the features that you wish, or to integrate this tool into your toolchain. If in doubt, just press the 💗sponsor button.