MongoDB Documentation, Release 3.0.4 Downgrade Limitations Once upgraded to MongoDB 3.0, you cannot downgrade to a version lower than 2.6.5 . If you upgrade to 3.0 and have run authSchemaUpgrade , you cannot downgrade to 2.6 without disabling --auth or restoring a pre-upgrade backup, as authSchemaUpgrade discards the MONGODB-CR credentials used in 2.6. See Upgrade Existing MONGODB-CR Users to Use SCRAM-SHA-1 (page 817). Upgrade Standalone mongod Instance to MongoDB 3.0 The following steps outline the procedure to upgrade a standalone mongod from version 2.6 to 3.0. To upgrade from version 2.4 to 3.0, upgrade to version 2.6 (page 866) first , and then use the following procedure to upgrade from 2.6 to 3.0. Upgrade Binaries If you installed MongoDB from the MongoDB apt , yum , or zypper repositories, you should upgrade to 3.0 using your package manager. Follow the appropriate installation instructions (page 6) for your Linux system. This will involve adding a repository for the new release, then performing the actual upgrade. Otherwise, you can manually upgrade MongoDB: Step 1: Download 3.0 binaries. Download binaries of the latest release in the 3.0 series from the MongoDB Down- load Page$^{255}$. See Install MongoDB (page 5) for more information. Step 2: Replace 2.6 binaries. Shut down your mongod instance. Replace the existing binary with the 3.0 mongod binary and restart mongod . Change Storage Engine to WiredTiger To change storage engine to WiredTiger, you will need to manually export and upload the data using mongodump and mongorestore . Step 1: Start 3.0 mongod . Ensure that the 3.0 mongod is running with the default MMAPv1 engine. Step 2: Export the data using mongodump . mongodump --out <exportDataDestination> Specify additional options as appropriate, such as username and password if running with authorization enabled. See mongodump for available options. Step 3: Create data directory for WiredTiger. Create a new data directory for WiredTiger. Ensure that the user account running mongod has read and write permissions for the new directory. mongod with WiredTiger will not start with data files created with a different storage engine. Step 4: Restart the mongod with WiredTiger. Restart the 3.0 mongod , specifying wiredTiger as the --storageEngine and the newly created data directory for WiredTiger as the --dbpath . Specify additional options as appropriate. mongod --storageEngine wiredTiger --dbpath <newWiredTigerDBPath> You can also specify the options in a configuration file . To specify the storage engine, use the new storage.engine setting. 811 12.1. Current Stable Release $^{255}$http://www.mongodb.org/downloads?jmp=docs Upgrade MongoDB Processes