Usage through zerotier VPN

[DavHau]

Is your feature request related to a problem? Please describe.

I did not manage to use nixos-anywhere on a host that can only be reached via a zerotier VPN

Describe the solution you'd like

Apply the host's configuration to the kexec installer, so that the installer can be reached through the VPN

Additional context

I have tried to apply my hosts nixos configuration to the installer via this nixos module that I import into the hosts config:
anywhere-installer.nix:

{extendModules, inputs, lib, ...}: let
  extendedNixos = extendModules {
    modules = [
      (inputs.nixos-images + /nix/kexec-installer/module.nix)
    ];
  };
in {
  system.build.anywhereVm = extendedNixos.config.system.build.vm;
  system.build.anywhereInstaller =
    lib.mkForce extendedNixos.config.system.build.kexecTarball;
}

... and then use nixos-anywhere like this:

nix run github:numtide/nixos-anywhere -- --flake .#my-machine root@10.241.225.42 --kexec $(nix build .#nixosConfigurations.my-machine.config.system.build.anywhereInstaller --print-out-paths)/*

... but the machine did not join the zerotier network. Not sure why. I could not debug this further as this was a remote machine.

It would be nice to have a VM test for the full nixos-anywhere installation. As of now there is only one for the formatting AFAIK.
Being able to test custom installers would be important, because when trying on a real host there is always only one shot unti the machine is stuck.

[Mic92]

That will not be visible with the current design because we use the nixos VM test framework that has no access to the internet.