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mongodb / v3.6 / reference / reference-command-copydb.html

copydb

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Definition

copydb

Copies a database either from one mongod instance to the current mongod instance or within the current mongod. Run copydb in the admin database of the destination server with the following syntax:

{ copydb: 1,
  fromhost: <hostname>,
  fromdb: <database>,
  todb: <database>,
  slaveOk: <bool>,
  username: <username>,
  nonce: <nonce>,
  key: <key>,
  writeConcern: <document>,
  bypassDocumentValidation: <boolean> }

copydb accepts the following options:

Field Type Description
fromhost string Optional. The hostname of the source mongod instance. Omit to copy databases within the same mongod instance.
fromdb string Name of the source database.
todb string Name of the target database.
slaveOk boolean Optional. Set slaveOK to true to allow copydb to copy data from secondary members as well as the primary. fromhost must also be set.
username string

Optional. The name of the user on the fromhost MongoDB instance. The user authenticates to the fromdb.

For more information, see Authentication to Source mongod Instance.
nonce string

Optional. A single use shared secret generated on the remote server, i.e. fromhost, using the copydbgetnonce command.

For more information, Generate nonce and key.
key string Optional. A hash of the password used for authentication. For more information, Generate nonce and key.
writeConcern document Optional. A document that expresses the write concern for the operation. Omit to use the default write concern.
bypassDocumentValidation boolean

Optional. Enables copydb to bypass document validation during the operation. This lets you insert documents that do not meet the validation requirements.

New in version 3.2.

The mongo shell provides the db.copyDatabase() wrapper for the copydb command.

When authenticating to the fromhost instance, copydb uses MONGODB-CR mechanism to authenticate the fromhost user. To authenticate users with SCRAM-SHA-1 mechanism, use the db.copyDatabase() method.

Behavior

Feature Compatibility Version

You cannot copy data between a mongod instance with featureCompatibilityVersion (FCV) 3.6 and a MongoDB version 3.4 and earlier mongod instance.

For example:

Instance 1 Instance 2  
Version 3.6 mongod with FCV 3.6 Version 3.6 mongod with FCV 3.6 Can copy data.
Version 3.6 mongod with FCV 3.6 Version 3.6 mongod with FCV 3.4 Can copy data.
Version 3.6 mongod with FCV 3.6 Version 3.4 mongod with FCV 3.4 Cannot copy data. Instance 2 must be a MongoDB version 3.6
Version 3.6 mongod with FCV 3.4 Version 3.4 mongod with FCV 3.4 Can copy data.
Version 3.6 mongod with FCV 3.4 Version 3.2 mongod Can copy data.

Operations that copy data include:

Destination

  • Run copydb in the admin database of the destination mongod instance, i.e. the instance receiving the copied data.
  • copydb creates the target database if it does not exist.
  • If the target database exists and no collection from the source database exists in the target database, copydb copies the collections from the source database to the target database. If any collection from the source database exists in the target database, copydb errors out and does not copy any remaining collections from the source database.
  • copydb requires enough free disk space on the host instance for the copied database. Use the db.stats() operation to check the size of the database on the source mongod instance.

Authentication to Source mongod Instance

For more information on required access and authentication, see Required Access.

Concurrency

  • copydb and clone do not produce point-in-time snapshots of the source database. Write traffic to the source or destination database during the copy process will result in divergent data sets.
  • copydb does not lock the destination server during its operation, so the copy will occasionally yield to allow other operations to complete.

Indexes

MongoDB performs foreground builds of indexes on databases copied via copydb. Foreground index builds lock the database and prevent all other operations on that database until the foreground build completes. There may also be a performance impact on other databases while the indexes build.

You can keep track of ongoing index creation operations with the db.currentOp() command.

Replica Sets

With read preference configured to set the slaveOk option to true, you may run copydb on a secondary member of a replica set.

Sharded Clusters

  • Do not use copydb from a mongos instance.
  • Do not use copydb to copy databases that contain sharded collections.

Required Access

Changed in version 2.6.

If the mongod instance of the source database (fromdb) enforces access control, you must have proper authorization for the source database.

If copying from another mongod instance (fromhost) that enforces access control, then you must authenticate to the fromhost instance by specifying the username, nonce, and key.

When authenticating to the fromhost instance, copydb uses the fromdb as the authentication database for the specified user.

When authenticating to the fromhost instance, copydb uses MONGODB-CR mechanism to authenticate the fromhost user. To authenticate users with SCRAM-SHA-1 mechanism, use the db.copyDatabase() method.

Source Database (fromdb)

Source is non-admin Database

Changed in version 3.0.

If the source database is a non-admin database, you must have privileges that specify find, listCollections, and listIndexes actions on the source database, and find action on the system.js collection in the source database.

{ resource: { db: "mySourceDB", collection: "" }, actions: [ "find", "listCollections", "listIndexes" ] },
{ resource: { db: "mySourceDB", collection: "system.js" }, actions: [ "find" ] },

Source is admin Database