I encountered the following warning after converting a mongodb replica set to a stand alone server. I did rs.remove('host') and removed the replSet arguments when starting the mongo db.
[root@sam ~]# mongo
MongoDB shell version: 2.4.3
connecting to: test
Server has startup warnings:
Tue Jul 9 17:18:46.076 [initandlisten]
Tue Jul 9 17:18:46.076 [initandlisten] ** WARNING: mongod started without --replSet yet 1 documents are present in local.system.replset
Tue Jul 9 17:18:46.077 [initandlisten] ** Restart with --replSet unless you are doing maintenance and no other clients are connected.
Tue Jul 9 17:18:46.077 [initandlisten] ** The TTL collection monitor will not start because of this.
Tue Jul 9 17:18:46.077 [initandlisten] ** For more info see http://dochub.mongodb.org/core/ttlcollections
Tue Jul 9 17:18:46.077 [initandlisten]
>
Please help. Need to fixed it immediately. Thanks.
The local database contains replica set information among other things. You can drop the local database without ill effect.
Use the following comments to drop the local database.
use local
db.dropDatabase()
The warning messages should go away after restarting mongod
use local;
db.dropDatabase();
db.system.replset.remove ({});
Quit the mongo shell .. restart service just in case "service mongod restart"
mongo --host bind_ip --port bind_port
来源：https://stackoverflow.com/questions/17544713/encountered-a-mongodb-warning-after-converting-a-replica-set-to-stand-alone-serv