anchor.diff:          type = types.bool;
           example = "true";
           description = ''
  -          Run smartd from the smartmontools package.
  +          Run smartd from the smartmontools package. Note that e-mail
  +          notifications will not be enabled unless you configure the list of
  +          devices with <varname>services.smartd.devices</varname> as well.
           '';
         };
   
  +      devices = mkOption {
  +        default = [];
  +        example = ["/dev/sda" "/dev/sdb"];
  +        description = ''
  +          List of devices to monitor. By default -- if this list is empty --,
  +          smartd will monitor all devices connected to the machine at the time
  +          it's being run. Configuring this option has the added benefit of
  +          enabling e-mail notifications to "root" every time smartd detects an
  +          error.
  +        '';
  +       };
       };
   
     };
  
positive.code: let
  
    cfg = config.services.smartd;
  
  in
  
  
negative.code: 
          daemonType = "daemon";
  
          exec = "${pkgs.smartmontools}/sbin/smartd --pidfile=/var/run/smartd.pid ${smartdFlags}";
        };
  
    };
  