mongodump Behavior, Access, and Usage

Using mongodump Without an authSource

When authSource is not specified in the MongoDB URI, the database name specified in --db is used both to authenticate your mongodump session and to indicate the database being dumped. For an example of using a different database for authentication when using mongodump, see Authenticating with a Specific Database.

Restore to Matching Server Version

When using mongorestore to load data files created by mongodump, the MongoDB versions of your source and destination deployments must be either:

• The same major version.

• The same feature compatibility version.

For example, if your dump was created from a MongoDB deployment running version 4.4, the MongoDB deployment you restore to must also run version 4.4 or have its FCV set to 4.4.

To change your feature compatibility version, see setFeatureCompatibilityVersion.

In addition, ensure that you are using the same version of mongorestore to load the data files as the version of mongodump that you used to create them. For example, if you used mongodump version 100.9.0 to create the dump, use mongorestore version 100.9.0 to restore it.

Read Preference

By default, mongodump uses read preference primary. To override the default, you can specify the read preference in the --readPreference command-line option or in the --uri connection string.

If read preference is specified in both the URI string and the --readPreference option, the --readPreference value overrides the read preference specified in the URI string.

Data Exclusion

If you specify both the --db and the --collection options, mongodump dumps the specified collection.

If you only specify the --db option, mongodump dumps that database with the following exclusions:

• If the value of --db is admin:

  • If you aren't connected to an Atlas Proxy, mongodump dumps the database but excludes the system.keys collection.

  • If you're connected to an Atlas Proxy, mongodump attempts to dump the database but errors out.

• If the value of --db is config, mongodump dumps all collections in that database.

• If the value of --db is local, mongodump dumps all collections in that database.

• For all other databases, mongodump excludes all collections that start with system., except for system.js.

If you omit the --db option, the following exclusions apply:

• mongodump excludes the local database.

• mongodump only includes the following collections in the output for the config database:

  • chunks

  • collections

  • databases

  • settings

  • shards

  • tags

  • version

• If you're connected to an Atlas Proxy, mongodump excludes the admin database.

mongodump output:

• Contains the documents in the database and the index definitions.

• Does not contain the index data.

mongorestore or mongod must rebuild the indexes after restoring data.

If you're using views:

• By default, mongodump only exports a view's metadata. mongodump doesn't create a binary export of the documents included in the view.

• To export the documents in a view, use --viewsAsCollections.

Metadata Output

If mongodump outputs to a directory, the output contains collection metadata which includes the following properties:

• Collection names

• Collection types

• Collection configuration options

• UUIDs

• Indexes

If mongodump outputs to standard output (stdout), the output does not include metadata. For more information, see the --out option.

Metadata Format

mongodump uses Extended JSON v2.0 (Canonical) format for the metadata files. To parse these files for restore, use mongorestore, which supports Extended JSON v2.0 (Canonical or Relaxed mode) format.

Overwrite Files

mongodump overwrites output files if they exist in the backup data folder. Before running the mongodump command multiple times, either ensure that you no longer need the files in the output folder (the default is the dump/ folder) or rename the folders or files.

mongodump During Resharding

mongodump fails if:

• mongodump is initiated when a resharding operation is in progress.

• The reshardCollection command is run during a mongodump operation.

Data Compression Handling

When run against a mongod instance that uses the WiredTiger storage engine, mongodump outputs uncompressed data.

Working Set

mongodump can adversely affect performance of the mongod. If your data is larger than system memory, mongodump will push the working set out of memory.

FIPS

mongodump automatically creates FIPS-compliant connections to a mongod/mongos that is configured to use FIPS mode.

Using mongodump on Atlas Free and Shared Tier Clusters

On free (M0) and shared (M2 and M5) tier Atlas clusters, the following limitations apply:

• You can't run mongodump on the admin database. By default, mongodump skips this database. If you use the --db option to set the destination database to admin, the program returns an error.

• You can't use the following options with the mongodump program:

  • --dumpDbUsersAndRoles

  • --oplog

Standalone Deployments and Replica Sets

For standalone or a replica set, mongodump can be a part of a backup strategy with mongorestore for partial backups based on a query, syncing from production to staging or development environments, or changing the storage engine of a standalone.

For details on using mongodump with mongorestore as part of a backup and recovery strategy, see:

• Back Up and Restore with MongoDB Tools

• MongoDB Backup Methods

Sharded Clusters

mongodump and mongorestore cannot be part of a backup strategy for 4.2+ sharded clusters that have sharded transactions in progress, as backups created with mongodump do not maintain the atomicity guarantees of transactions across shards.

For 4.2+ sharded clusters with in-progress sharded transactions, use one of the following coordinated backup and restore processes which do maintain the atomicity guarantees of transactions across shards:

• MongoDB Atlas,

• MongoDB Cloud Manager, or

• MongoDB Ops Manager.