Declarative Virtual Machines

You can declare virtual machines directly in the host’s NixOS configurations by adding microvm.vms.<name> entries in a module.

nixos-rebuild switch then builds, updates, and starts them via systemd. You can’t modify VMs with microvm CLI anymore if you use the declarative workflow.

See Declarative MicroVMs for the upstream option reference.

Declare Multiple Virtual Machines

Note

Before continuing, make sure you’ve completed the Host Setup.

Create a virtualization.nix module and import it into your host setup:

{
  config,
  pkgs,
  mariner,
  nixpkgs,
  ...
}:
{
  microvm.vms = {
    vm-work = {
      specialArgs = { inherit nixpkgs; };
      config =
        { config, pkgs, ... }: # this points to the vm config to access config.mariner
        {
          imports = builtins.attrValues mariner.nixosModules ++ [ ];
          mariner.cid = 4;
          mariner.username = "work";
          mariner.hostAuthorizedKey = "ssh-ed25519 AAAA... your@host";
        };
    };

    vm-test = {
      specialArgs = { inherit nixpkgs; };
      config =
        { config, pkgs, ... }: # this points to the vm config to access config.mariner
        {
          imports = builtins.attrValues mariner.nixosModules ++ [ ];
          mariner.cid = 5;
          mariner.username = "user";
          mariner.hostAuthorizedKey = "ssh-ed25519 AAAA... your@host";
        };
    };
  };
}

Import the modules into your host configurations:

# In another module:
  imports = [
    modules/virtualization.nix
  ];

# Or in host flake:
  nixosConfigurations.machine = nixpkgs.lib.nixosSystem {
    #...
    modules = [
      modules/virtualization.nix
      # ...
    ];
  };

nixos-rebuild switch should build each VM and start the systemd services microvm@<name>.service

Now you can ssh into them if the services are running:

ssh work@vsock%4
ssh user@vsock%5

See microvm.autostart for starting the VMs automatically at host boot.