replSetInitiate¶

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IP Binding
Example

replSetInitiate¶

The replSetInitiate command initializes a new replica set.

To run replSetInitiate, use the db.runCommand( { <command> } ) method.

Note

Run the command on only one of the mongod instances for the replica set.

Use the following syntax:

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{ replSetInitiate : <config_document> }

The <config_document> is a document that specifies the replica set’s configuration. For instance, here’s a config document for creating a simple 3-member replica set:

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{
    _id : <setname>,
     members : [
         {_id : 0, host : <host0>},
         {_id : 1, host : <host1>},
         {_id : 2, host : <host2>},
     ]
}

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.

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:

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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:

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mongo --host My-Example-Associated-Hostname

mongo --host 198.51.100.1

Example¶

Assign a config document to a variable and then to pass the document to the rs.initiate() helper:

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config = {
    _id : "my_replica_set",
     members : [
         {_id : 0, host : "rs1.example.net:27017"},
         {_id : 1, host : "rs2.example.net:27017"},
         {_id : 2, host : "rs3.example.net", arbiterOnly: true},
     ]
}

rs.initiate(config)

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.

Notice that omitting the port cause the host to use the default port of 27017. Notice also that you can specify other options in the config documents such as the arbiterOnly setting in this example.