MongoDB Documentation, Release 3.0.4 Procedure Run authSchemaUpgrade command. 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. Requirements To upgrade the authorization model, you must have a user in the admin database with the role userAdminAnyDatabase (page 412). Step 1: Connect to MongoDB instance. Connect and authenticate to the mongod instance for a single deployment or a mongos for a sharded cluster as an admin database user with the role userAdminAnyDatabase (page 412). Step 2: Upgrade authorization schema. Use the authSchemaUpgrade command in the admin database to update the user data using the mongo shell. db.getSiblingDB("admin").runCommand({authSchemaUpgrade: 1 }); In case of error, you may safely rerun the authSchemaUpgrade command. Sharded cluster authSchemaUpgrade consideration. For a sharded cluster, authSchemaUpgrade will up- grade the authorization data of the shards as well and the upgrade is complete. You can, however, override this behavior by including upgradeShards: false in the command, as in the following example: db.getSiblingDB("admin").runCommand({authSchemaUpgrade: 1, upgradeShards: false }); If you override the behavior, 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 All users in a 2.6 system are stored in the admin.system.users (page 291) collection. To manipulate these users, use the user management methods . The upgrade procedure copies the version 2.4 admin.system.users collection to admin.system.backup_users . The upgrade procedure leaves the version 2.4 <database>.system.users collection(s) intact. Downgrade MongoDB from 2.6 Before you attempt any downgrade, familiarize yourself with the content of this document, particularly the Downgrade Recommendations and Checklist (page 871) and the procedure for downgrading sharded clusters (page 876). Downgrade Recommendations and Checklist When downgrading, consider the following: Downgrade Path Once upgraded to MongoDB 2.6, you cannot downgrade to any version earlier than MongoDB 2.4. If you created text or 2dsphere indexes while running 2.6, you can only downgrade to MongoDB 2.4.10 or later. 871 12.2. Previous Stable Releases