nixos-config/users/root/default.nix

{ pkgs, ... }:
{
  users.users.root = {
    initialHashedPassword = "";
    openssh.authorizedKeys.keyFiles = [
      (pkgs.fetchurl {
        url = "https://github.com/eboskma.keys";
        sha256 = "5pkayHiDL5JfXqAmTGtaYpbrjIjHFHyJWOLnM4yqgK0=";
      })
    ];
  };
}