Prerequisites
Before setting up the MongoDB 6.0.10 replica set, ensure you have completed the following prerequisites:
Step 1: Install MongoDB 6.0.10
Install MongoDB 6.0.10 using the provided script:
sudo apt-get install gnupg curl -y
# Import the MongoDB public GPG Key
curl -fsSL <https://pgp.mongodb.com/server-6.0.asc> | \
sudo gpg -o /usr/share/keyrings/mongodb-server-6.0.gpg \
–dearmor
# Create a list file for MongoDB
echo “deb [ arch=amd64,arm64 signed-by=/usr/share/keyrings/mongodb-server-6.0.gpg ] <https://repo.mongodb.org/apt/ubuntu> jammy/mongodb-org/6.0 multiverse” | sudo tee /etc/apt/sources.list.d/mongodb-org-6.0.list
# Update package list and install MongoDB
sudo apt-get update
sudo apt-get install mongodb-org -y
Step 2: Add Hosts and Configure Server Hostnames
Add the hostnames and IP addresses of all three servers to the /etc/hosts file on each server. Use this example as a reference:
192.168.1.22 secondary1.mongo
192.168.1.23 secondary2.mongo
Step 3: Test Hostname Resolution
Ping each server from every other server using their hostnames to verify hostname resolution. Example:
ping secondary1.mongo
ping secondary2.mongo
Step 4: Create Admin User (If Not Enabled)
If you didn’t enable authentication during MongoDB installation, create an admin user.
Example:
mongosh –host <Hostname or IP of each>:27017
# Switch to the admin database
use admin
# Create an admin user with appropriate roles
db.createUser({
user: “admin”,
pwd: “your_password”,
roles: [
“userAdminAnyDatabase”,
“dbAdminAnyDatabase”,
“readWriteAnyDatabase”,
“root”
]
})
Replace “your_password” with a secure password for the admin user.
Step 5: Enable Security with Keyfile
Generate a key and store it at /etc/mongodb/keys/mongo-key,
Just copy & paste the below command on all three servers:
sudo chmod 600 /etc/mongodb/keys/mongo-key
Step 6: Restart MongoDB and Check Status
Restart MongoDB on all servers and check the status:
sudo service mongod status
Step 7: Test Connectivity (Optional)
Log in to MongoDB and check if it’s working:
Let’s begin with ReplicaSet Configuration
Now proceed with the main setup steps:
Step 1: Update MongoDB Configuration Files
On each server, update the MongoDB configuration file /etc/mongod.conf with the provided example:
dbPath: /opt/mongodb
systemLog:
destination: file
logAppend: true
path: /var/log/mongodb/mongod.log
net:
port: 27017
bindIp: 0.0.0.0
processManagement:
timeZoneInfo: /usr/share/zoneinfo
fork: true
security:
authorization: enabled
keyFile: /etc/mongodb/keys/mongo-key
transitionToAuth: true
replication:
replSetName: rs111
Step 2: Start MongoDB on Each Server
Start MongoDB on each server using the following command:
sudo service mongod status
Step 3: Connect to Primary’s Mongo Shell (mongosh or mongo)
Connect to one of the MongoDB servers using the MongoDB shell (mongosh). Example:
Replace server_ip with the IP address of the server you want to connect to.
Step 4: Initialize the Replica Set
Inside the MongoDB shell, initialize the replica set with the chosen name (rs111). Run this command on the server you want as the primary. Example:
_id: “rs111“,
members: [
{ _id: 0, host: “primary.mongo:27017“ },
{ _id: 1, host: “secondary1.mongo:27017“ },
{ _id: 2, host: “secondary2.mongo:27017“ }
]
})
Replace primary_hostname, secondary1_hostname, and secondary2_hostname with the hostnames of your servers. The primary should be the server where you run this command.
Step 5: Verify Replica Set Status
Verify the status of the replica set by running the following command in the MongoDB shell:
To check the status of replicaSet
Troubleshooting Common Issues & Notes
Issue 1: “no reachable/healthy members” or “STARTUP” state
Solution: If you encounter these issues, it means that one or more replica set members are not reachable or are still in the startup process. Check network connectivity, MongoDB status, and logs.
sudo less /var/log/mongodb/mongod.log
Solution: Check /etc/hosts in each server, are all three hostnames added and are they using correct IP Addresses.
192.168.1.21 primary.mongo
192.168.1.22 secondary1.mongo
192.168.1.23 secondary2.mongo
Solution: If nothing works reconfigure replicaSet using correct IP Addresses.
Connect to the primary node of your replica set using the mongo shell:
Replace primary_ip with the IP address of your primary node.
In the mongo shell, execute the following command to obtain the current replica set configuration:
This command stores the current replica set configuration in the cfg variable.
Edit the cfg variable to update the hostnames with their respective IP addresses. You will need to modify the host field for each member in the configuration. For example:
cfg.members[1].host = “192.168.1.22:27017”;
cfg.members[2].host = “192.168.1.23:27017”;
Replace primary_ip, secondary1_ip, and secondary2_ip with the actual IP addresses and port numbers for your servers.
After making the necessary changes, reconfigure the replica set using the updated cfg variable:
This command will apply the modified configuration to the replica set.
To ensure that the changes are applied successfully, you can check the replica set status using:
Verify that the hostnames have been updated with the correct IP addresses in the replica set configuration.
Make sure to execute these commands carefully and replace the placeholders with your actual server IP addresses and port numbers.
Issue 2: Authentication Errors
Solution: If you encounter authentication errors, ensure valid credentials are provided when connecting to MongoDB. Verify user privileges, or check if you’ve created an admin user in secondary servers.
Additional Notes:
Use 0.0.0.0 for bindIp only if you’ve enabled authentication by adding an admin user in the admin database of all MongoDB instances.
You can change default “dbPath: /var/lib/mongodb” or choose a different path like “dbPath: /opt/mongodb” in mongod.conf file.
