anchor.diff:          default = "0.0.0.0:9090";
           description = ''
             Address to listen on for the web interface, API, and telemetry.
  +        '';
  +      };
  +
  +      stateDir = mkOption {
  +        type = types.str;
  +        default = "prometheus2";
  +        description = ''
  +          Directory below <literal>${stateDirBase}</literal> to store Prometheus metrics data.
  +          This directory will be created automatically using systemd's StateDirectory mechanism.
  +          Defaults to <literal>prometheus2</literal>.
           '';
         };
   
  
positive.code:     in promtoolCheck "check-config" "prometheus.yml" yml;
  
    cmdlineArgs = cfg.extraFlags ++ [
      "-storage.local.path=/var/lib/prometheus/metrics"
      "-config.file=${prometheusYml}"
      "-web.listen-address=${cfg.listenAddress}"
      "-alertmanager.notification-queue-capacity=${toString cfg.alertmanagerNotificationQueueCapacity}"
  
negative.code:               concatStringsSep " \\\n  " cmdlineArgs);
            User = promUser;
            Restart  = "always";
            WorkingDirectory = workingDir;
            StateDirectory = stateDir;
          };
        };
      })
  