systemctl enable systemd-nspawn@archlinux

services.systemd-nspawn@archlinux.enable = true;

    If set to false, this unit will be a symlink to /dev/null. This is primarily useful to prevent specific template instances (e.g. serial-getty@ttyS0) from being started. Note that enable=true does not make a unit start by default at boot; if you want that, see wantedBy.

{config, pkgs, ...}:
{
  systemd.targets.machines.enable = true;
  #services.systemd-nspawn@archlinux = true;

  systemd.nspawn.archlinux = {
    enable = true;    
    wantedBy = [ "machines.target" ];
    execConfig = { 
      Boot = true; 
      LimitCPU = "150%";
    };
    filesConfig.Bind = ["/media/storage/buildbot/packages:/output"];
    networkConfig.VirtualEthernet = false;
  };
}