Esto se debe a que las credenciales de usuario se almacenan en la base de datos de administración y no en la base de datos predeterminada a la que se conecta el shell mongo (prueba).
Puede cambiar esto con la URL de conexión:
Con el admin base de datos:
$ mongo localhost/admin --username user -p
MongoDB shell version: 2.6.9
Enter password:
connecting to: localhost/admin
replset:PRIMARY>
Sin una base de datos específica (test por defecto):
$ mongo localhost --username user -p
MongoDB shell version: 2.6.9
Enter password:
connecting to: localhost
2015-04-22T15:34:28.743+0100 Error: 18 { ok: 0.0, errmsg: "auth failed", code: 18 } at src/mongo/shell/db.js:1260
exception: login failed
Con --authenticationDatabase :
$ mongo localhost --username user --authenticationDatabase admin -p
MongoDB shell version: 2.6.9
Enter password:
connecting to: localhost
replset:PRIMARY>
Tenga en cuenta que usar --host no asumirá que el nombre de la base de datos es el que está después de / (barra oblicua:
$ mongo --host localhost/admin --username user -p
MongoDB shell version: 2.6.9
Enter password:
connecting to: localhost/admin:27017/test
2015-04-22T15:37:40.703+0100 starting new replica set monitor for replica set localhost with seeds admin:27017
2015-04-22T15:37:40.703+0100 [ReplicaSetMonitorWatcher] starting
2015-04-22T15:37:40.920+0100 getaddrinfo("admin") failed: nodename nor servname provided, or not known
2015-04-22T15:37:40.922+0100 warning: No primary detected for set localhost
2015-04-22T15:37:40.922+0100 All nodes for set localhost are down. This has happened for 1 checks in a row. Polling will stop after 29 more failed checks
2015-04-22T15:37:40.923+0100 Error: connect failed to replica set localhost/admin:27017 at src/mongo/shell/mongo.js:148
exception: connect failed
