mongos> use admin switched to db admin mongos> db.createUser({user: "alex" , pwd: "pass" , roles:[{db: "whatever" , role: "readWrite" }]}) Successfully added user: { "user" : "alex" , "roles" : [ { "db" : "whatever" , "role" : "readWrite" } ] } Authenticating as the new user: mongos> db.auth( "alex" , "pass" ) 1 Notice the misspelled database name: mongos> use whatever3 switched to db whatever3 And, as expected, trying to access the misspelled database does not work: mongos> db.coll.find() Error: error: { "$err" : "not authorized for query on whatever3.coll" , "code" : 13 } Switch back to being admin user mongos> use admin switched to db admin mongos> db.auth( "admin" , "pass" ) 1 mongos> sh.status() --- Sharding Status --- sharding version: { "_id" : 1, "minCompatibleVersion" : 5, "currentVersion" : 6, "clusterId" : ObjectId( "552424ff8024973cf28217f2" ) } shards: { "_id" : "shard0000" , "host" : "localhost:27019" } balancer: Currently enabled: yes Currently running: no Failed balancer rounds in last 5 attempts: 0 Migration Results for the last 24 hours: No recent migrations databases: { "_id" : "admin" , "partitioned" : false , "primary" : "config" } { "_id" : "whatever" , "partitioned" : false , "primary" : "shard0000" } { "_id" : "whatever3" , "partitioned" : false , "primary" : "shard0000" } And notice in the above that although user alex did not have access to whatever3 database,whatever3 was still created in config database – definitely a source of confusion. mongos> show dbs admin 0.016GB config 0.016GB mongos> use config switched to db config mongos> db.databases.find() { "_id" : "admin" , "partitioned" : false , "primary" : "config" } { "_id" : "whatever" , "partitioned" : false , "primary" : "shard0000" } { "_id" : "whatever3" , "partitioned" : false , "primary" : "shard0000" }