rs.initiate()
Description
rs.initiate(configuration)Initiates a replica set. Optionally, the method can take an argument in the form of a document that holds the configuration of a replica set.
Important
mongo Shell Method
This page documents a
mongomethod. This is not the documentation for database commands or language-specific drivers, such as Node.js. To use the database command, see thereplSetInitiatecommand.For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.
The
rs.initiate()method has the following parameter:ParameterTypeDescriptionconfigurationdocumentOptional. A document that specifies configuration for the new replica set. If a configuration is not specified, MongoDB uses a default replica set configuration.
IP Binding
Starting in MongoDB 3.6, MongoDB binaries, mongod and
mongos, bind to localhost by default. If the
net.ipv6 configuration file setting or the --ipv6
command line option is set for the binary, the binary additionally binds
to the localhost IPv6 address.
Previously, starting from MongoDB 2.6, only the binaries from the official MongoDB RPM (Red Hat, CentOS, Fedora Linux, and derivatives) and DEB (Debian, Ubuntu, and derivatives) packages bind to localhost by default.
When bound only to the localhost, these MongoDB 3.6 binaries can only
accept connections from clients (including the mongo shell,
other members in your deployment for replica sets and sharded clusters)
that are running on the same machine. Remote clients cannot connect to
the binaries bound only to localhost.
To override and bind to other ip addresses, you can use the
net.bindIp configuration file setting or the
--bind_ip command-line option to specify a list of hostnames or ip
addresses.
Warning
Before binding to a non-localhost (e.g. publicly accessible) IP address, ensure you have secured your cluster from unauthorized access. For a complete list of security recommendations, see Security Checklist. At minimum, consider enabling authentication and hardening network infrastructure.
For example, the following mongod instance binds to both
the localhost and the hostname My-Example-Associated-Hostname, which is
associated with the ip address 198.51.100.1:
mongod --bind_ip localhost,My-Example-Associated-Hostname
In order to connect to this instance, remote clients must specify
the hostname or its associated ip address 198.51.100.1:
mongo --host My-Example-Associated-Hostname mongo --host 198.51.100.1
Replica Set Configuration
See Replica Set Configuration Document Example for details of replica set configuration document.
Tip
When possible, use a logical DNS hostname instead of an ip address, particularly when configuring replica set members or sharded cluster members. The use of logical DNS hostnames avoids configuration changes due to ip address changes.
Example
The following example initiates a new replica set with three members.
The three mongod instances must have started with the
--replSet command line option (or
replication.replSetName if using a configuration file) set
to myReplSet and the --bind_ip (or net.bindIp
if using a configuration file) set appropriately such that other
members of the replica set and clients can connect.
Warning
Before binding to a non-localhost (e.g. publicly accessible) IP address, ensure you have secured your cluster from unauthorized access. For a complete list of security recommendations, see Security Checklist. At minimum, consider enabling authentication and hardening network infrastructure.
Connect a mongo shell to one of the mongod
instances and run rs.initiate().
Note
Run rs.initiate() on just one and only one
mongod instance for the replica set.
Tip
When possible, use a logical DNS hostname instead of an ip address, particularly when configuring replica set members or sharded cluster members. The use of logical DNS hostnames avoids configuration changes due to ip address changes.
rs.initiate( { _id: "myReplSet", version: 1, members: [ { _id: 0, host : "mongodb0.example.net:27017" }, { _id: 1, host : "mongodb1.example.net:27017" }, { _id: 2, host : "mongodb2.example.net:27017" } ] } )
For details on replica set configuration, see Replica Set Configuration Fields.
For details on deploying a replica set, see Deploy a Replica Set.