1. It’s necessary to have a primary replica set up before establishing a secondary replica. Ensure there is a running primary replica.
1. Open the MongoDB shell. You can connect it to the MongoDB instance by typing \`\`\` mongo \`\`\` in the terminal.
1. In the MongoDB shell, type: \`\`\` rs.status() \`\`\` to check the status of your replica set.
1. If you don’t have any members in your replica set, add a new member using: \`\`\` rs.add(“SECONDARY_HOST:SECONDARY_PORT”) \`\`\`
Replace SECONDARY_HOST and SECONDARY_PORT with the corresponding for your secondary server.1. When you add the new member, MongoDB automatically assigns it as secondary. You can type `rs.status()` again to check the state of the new member.
Your secondary replica is now set up.
Please note that in the process, you might encounter some issues if you have not configured MongoDB’s replica set initially in your MongoDB config file. Make sure you have something like this in your mongodb.conf file:
\`\`\`
replication:
replSetName: “rs0“
\`\`\`
Also, check your MongoDB servers can talk to each other via the network.
Note: it is good practice to have an odd number of members in a replica set to maintain a majority during elections in case a member goes down. If you need data redundancy but not necessarily more voting members, you can also add an arbiter.
