anchor.diff:  
     config = mkIf cfg.updater.enable {
   
  -    services.fprot.updater.productData = "${pkgs.fprot}/opt/f-prot/product.data";
  -    services.fprot.updater.licenseKeyfile = "${pkgs.fprot}/opt/f-prot/license.key";
  +    services.fprot.updater.productData = mkDefault "${pkgs.fprot}/opt/f-prot/product.data";
  +    services.fprot.updater.licenseKeyfile = mkDefault "${pkgs.fprot}/opt/f-prot/license.key";
   
       environment.systemPackages = [ pkgs.fprot ];
       environment.etc = singleton {
  
positive.code: 
      services.fprot = {
        updater = {
  	enable = mkOption {
  	  default = false;
  	  description = ''
  	    Whether to enable automatic F-Prot virus definitions database updates.
  	  '';
  	};
  
  	productData = mkOption {
  	  description = ''
  	    product.data file. Defaults to the one supplied with installation package.
  	  '';
  	};
  
  	frequency = mkOption {
  	  default = 30;
  	  description = ''
  	    Update virus definitions every X minutes.
  	  '';
  	};
  
  	licenseKeyfile = mkOption {
  	  description = ''
  	    License keyfile. Defaults to the one supplied with installation package.
  	  '';
  	};
  
        };
      };
  
negative.code: 
      jobs = {
        fprot_updater = {
          name = "fprot-updater";
            task = true;
  
            # have to copy fpupdate executable because it insists on storing the virus database in the same dir
            preStart = ''
              mkdir -m 0755 -p ${stateDir}
              chown ${fprotUser}:${fprotGroup} ${stateDir}
              cp ${pkgs.fprot}/opt/f-prot/fpupdate ${stateDir}
              ln -sf ${cfg.updater.productData} ${stateDir}/product.data
            '';
            #setuid = fprotUser;
            #setgid = fprotGroup;
            exec = "/var/lib/fprot/fpupdate --keyfile ${cfg.updater.licenseKeyfile}";
        };
      };
  
   };
  
  }
  