anchor.diff:  
     config = mkIf (cfg4.enable || cfg6.enable) {
   
  -    users = {
  -      users.dhcpd = {
  -        isSystemUser = true;
  -        group = "dhcpd";
  -        description = "DHCP daemon user";
  -      };
  -      groups.dhcpd = {};
  -    };
  -
       systemd.services = dhcpdService "4" cfg4 // dhcpdService "6" cfg6;
   
     };
  
positive.code:       default = false;
        description = ''
          Whether to enable the DHCPv${postfix} server.
        '';
      };
  
      stateDir = mkOption {
        type = types.path;
        # We use /var/lib/dhcp for DHCPv4 to save backwards compatibility.
        default = "/var/lib/dhcp${if postfix == "4" then "" else postfix}";
        description = ''
          State directory for the DHCP server.
        '';
      };
  
  
negative.code: 
    imports = [
      (mkRenamedOptionModule [ "services" "dhcpd" ] [ "services" "dhcpd4" ])
    ] ++ flip map [ "4" "6" ] (postfix:
      mkRemovedOptionModule [ "services" "dhcpd${postfix}" "stateDir" ] ''
        The DHCP server state directory is now managed with the systemd's DynamicUser mechanism.
        This means the directory is named after the service (dhcpd${postfix}), created under
        /var/lib/private/ and symlinked to /var/lib/.
      ''
    );
  
    ###### interface
  
  