MongoDB Documentation, Release 3.0.4 Downgrade Binaries Once upgraded to MongoDB 3.0, you cannot downgrade to a version lower than 2.6.5 . The downgrade procedure for a sharded cluster reverses the order of the upgrade procedure. The version v6 config database is backwards compatible with MongoDB 2.6. Step 1: Disable the Balancer. Turn off the balancer (page 684) in the sharded cluster, as described in Disable the Balancer (page 717). Step 2: Downgrade each shard, one at a time. For each shard: 1. Downgrade the mongod secondaries before downgrading the primary. 2. To downgrade the primary, run replSetStepDown and downgrade. Step 3: Downgrade the config servers. Downgrade all 3 mongod config server instances, leaving the first system in the mongos --configdb argument to downgrade last . Step 4: Downgrade the mongos instances. Downgrade and restart each mongos , one at a time. The downgrade process is a binary drop-in replacement. Step 5: Re-enable the balancer. Once the upgrade of sharded cluster components is complete, re-enable the bal- ancer (page 718). General Downgrade Procedure Except as described on this page, moving between 2.6 and 3.0 is a drop-in replace- ment: Step 1: Stop the existing mongod instance. For example, on Linux, run 3.0 mongod with the --shutdown option as follows: Step 2: Start the new mongod instance. Ensure you start the 2.6 mongod with the same dbPath : To download MongoDB 3.0, go to the downloads page$^{282}$. Download See also: $^{282}$http://www.mongodb.org/downloads $^{283}$https://github.com/mongodb/mongo/blob/v3.0/distsrc/THIRD-PARTY-NOTICES Chapter 12. Release Notes 826 • All Third Party License Notices$^{283}$. Replace /var/mongod/data with your MongoDB dbPath . See also the Stop mongod Processes (page 225) for alternate methods of stopping a mongod instance. mongod --dbpath /var/mongod/data --shutdown mongod --dbpath /var/mongod/data Replace /var/mongod/data with your MongoDB dbPath . See Upgrade MongoDB to 3.0 (page 810) for full upgrade instructions.