anchor.diff:  
       environment.systemPackages = [ mongodb ];
   
  -    systemd.services.mongodb_init =
  -      { description = "MongoDB server initialisation";
  -
  -        wantedBy = [ "mongodb.service" ];
  -        before = [ "mongodb.service" ];
  -
  -        serviceConfig.Type = "oneshot";
  -
  -        script = ''
  -          if ! test -e ${cfg.dbpath}; then
  -              install -d -m0700 -o ${cfg.user} ${cfg.dbpath}
  -              install -d -m0755 -o ${cfg.user} `dirname ${cfg.logpath}`
  -          fi
  -        '';
  -      };
  -
       systemd.services.mongodb =
         { description = "MongoDB server";
   
  
positive.code:         description = "Location where MongoDB stores its files";
        };
  
        logpath = mkOption {
          default = "/var/log/mongodb/mongod.log";
          description = "Location where MongoDB stores its logfile";
        };
  
        logappend = mkOption {
          default = true;
          description = "Append logfile instead over overwriting";
        };
  
        replSetName = mkOption {
  
negative.code:           If this instance is part of a replica set, set its name here.
            Otherwise, leave empty to run as single node.
          '';
        };
  
        extraConfig = mkOption {
          default = "";
          example = ''
            nojournal = true
          '';
          description = "MongoDB extra configuration";
        };
      };
  
  