Question: How do you set up a MongoDB replica set on Ubuntu?

Answer

Setting up a MongoDB replica set on Ubuntu involves several steps, including installing MongoDB, configuring the replica set, and initializing it. Below is a comprehensive guide to get you started.

Step 1: Install MongoDB

First, update your Ubuntu's package database and install MongoDB.

sudo apt-get update
sudo apt-get install -y mongodb-org

Ensure MongoDB is started and enabled to start on boot:

sudo systemctl start mongod
sudo systemctl enable mongod

Step 2: Configure MongoDB for Replica Set

Edit the MongoDB configuration file, usually found at /etc/mongod.conf, to enable replica sets. You'll need to add or modify the replication section:

replication:
  replSetName: \"rs0\"

Here, rs0 is the name of your replica set. You can choose any name you prefer.

After making these changes, restart MongoDB:

sudo systemctl restart mongod

Step 3: Initialize the Replica Set

On the primary server, access the MongoDB shell:

mongo

In the MongoDB shell, initialize the replica set:

rs.initiate({
  _id : \"rs0\",
  members: [
    { _id: 0, host: \"your_primary_server_ip:27017\" }
  ]
})

Replace \"your_primary_server_ip\" with the actual IP address of your server. This command initializes the replica set with a single member (the primary server).

Step 4: Add Additional Members to the Replica Set

If you have additional servers you want to include in the replica set as secondary nodes, use the rs.add() command:

rs.add(\"your_secondary_server_ip:27017\")

Replace \"your_secondary_server_ip\" with the IP address of your secondary server.

Repeat this step for each secondary server you wish to add to the replica set.

Step 5: Verify Replica Set Configuration

To verify that your replica set is configured correctly and all members have been added, use the following command:

rs.status()

This command provides detailed information about the replica set configuration and status of each member.

Conclusion

You now have a MongoDB replica set running on Ubuntu. This setup enhances your database's availability and fault tolerance. Keep in mind that managing a replica set involves regular maintenance tasks such as monitoring performance, managing backups, and handling failovers.