MongoDB Documentation, Release 3.0.4 Replica Sets For a replica set, it is only necessary to run the upgrade process on the primary as the changes will automatically replicate to the secondaries. Sharded Clusters For a sharded cluster, connect to one mongos instance and run the upgrade procedure to upgrade the cluster’s authentication data. By default, the procedure will upgrade the authentication data of the shards as well. To override this behavior, run authSchemaUpgrade with the upgradeShards: false option. If you choose to override, you must run the upgrade procedure on the mongos first, and then run the procedure on the primary members of each shard. For a sharded cluster, do not run the upgrade process directly against the config servers (page 670). Instead, perform the upgrade process using one mongos instance to interact with the config database. Important: To use the SCRAM-SHA-1 authentication mechanism, a driver upgrade is necessary if your current driver version does not support SCRAM-SHA-1 . See required driver versions (page 819) for details. Step 1: Connect to the MongoDB instance. Connect and authenticate to the mongod instance for a single deploy- ment, the primary mongod for a replica set, or a mongos for a sharded cluster as an admin database user with the role userAdminAnyDatabase (page 412). Step 2: Upgrade authentication schema. Use the authSchemaUpgrade command in the admin database to update the user data using the mongo shell. db.adminCommand({authSchemaUpgrade: 1}); In case of error, you may safely rerun the authSchemaUpgrade command. Sharded cluster authSchemaUpgrade consideration. For a sharded cluster without shard local users (page 324), authSchemaUpgrade will, by default, upgrade the authorization data of the shards as well, completing the upgrade. You can, however, override this behavior by including upgradeShards: false in the command, as in the following example: If you override the default behavior or your cluster has shard local users, after running authSchemaUpgrade on a mongos instance, you will need to connect to the primary for each shard and repeat the upgrade process after upgrading on the mongos . Result After this procedure is complete, all users in the database will have SCRAM-SHA-1 -style credentials, and any subsequently-created users will also have this type of credentials. db.adminCommand( {authSchemaUpgrade: 1, upgradeShards: false } ); Warning: The procedure to upgrade to SCRAM-SHA-1 discards the such, the procedure is irreversible , short of restoring from backups. The procedure also disables MONGODB-CR as an authentication mechanism. Upgrade 2.6 MONGODB-CR Users to SCRAM-SHA-1 Run authSchemaUpgrade command. Chapter 12. Release Notes 820