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
impereratively with the provided microvm
command.
Warning: This is a Nix Flakes-only project. Use with nix-shell -p nixFlakes
- 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 thenixosModules
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.
Hypervisor | Language | Restrictions |
---|---|---|
qemu | C | |
cloud-hypervisor | Rust | no 9p shares |
firecracker | Rust | no 9p/virtiofs shares |
crosvm | Rust | no network interfaces |
kvmtool | C | no virtiofs shares |
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.
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.)
nix flake init -t 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#vm
Check networkctl status virbr0
for the DHCP leases of the
MicroVMs. They listen for ssh with an empty root password.
Your Flake does no longer need to provide the MicroVMs as packages. An
entry for each MicroVM in nixosConfiguration
is enough.
To get a MicroVM's hypervisor runner as a package, use:
nix build myflake#nixosConfigurations.my-microvm.config.microvm.runner.qemu
MicroVM parameters have moved inside the NixOS configuration, gaining
parameter validation through the module system. Refer to
nixos-modules/microvm/options.nix
for their definitions.
Delete the following remnants from 0.1.0:
microvm-run
microvm-shutdown
tap-interfaces
virtiofs
All these copied files are now behind the current
symlink to a
Hypervisor runner package.
At last, check the validity of the symlinks in
/nix/var/nix/gcroots/microvm
.
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 đź’—sponsor button.
- Boot with root off virtiofs, avoiding overhead of creating squashfs image
- Provide a writable
/nix/store
- Distribute/fail-over MicroVMs at run-time within a cluster of hosts