Converting StandAlone MongoDB to Replicaset

Table of Contents

Overview

Hi all, today i’ll show you how to convert standalone mongoDB mode to replicaset, in this post im just converting single instance.

Backup MongoDB

Before going further we need to backup all database, just in case s**t happen.

mkdir backup
mongodump --gzip --username adminmongo --password "mymongopassword" --host "localhost:27017" --out ~/backup/mongo/mongo-`date "+%d-%m-%Y"` --authenticationDatabase admin

Converting MongoDB to ReplicaSet

mongosh -u adminmongo -p  --authenticationDatabase admin
use admin
db.adminCommand(
   {
      shutdown: 1,
      comment: "Convert to cluster"
   }
)

change the configuration mongodb and set replica name like this

vi /etc/mongod.conf
----
security:
  authorization: enabled
  keyFile: /var/lib/mongodb/mongod.key
  
replication:
  replSetName: bippo

Create keyFile for authentication for each cluster.

openssl rand -base64 741 > /var/lib/mongod/mongod.key
chmod 400 /var/lib/mongod/mongod.key
chown mongod:mongod /var/lib/mongod/mongod.key

Before starting the service we need to edit current systemd configuration mongodDB file , because when i first time implement i got an error.

 'Environment variable MONGODB_CONFIG_OVERRIDE_NOFORK == 1, overriding "processManagement.fork" to false"'.

vi /lib/systemd/system/mongod.service
# uncomment this line
#Environment="MONGODB_CONFIG_OVERRIDE_NOFORK=1"

restart systemd and start mongodb

systemctl daemon-reload
systemctl start mongod; systemctl status mongod

mongosh -u adminmongo -p  --authenticationDatabase admin
> rs.initiate()
# to verify replicate use this command
rs.status()
# to check replicaset configuration
rs.config()

Connecting Apps using replicaSet string

This is an example of configuration client apps connecting to mongo replicaset

mongodb.uri=mongodb://adminmongo:mymongopassword@172.17.0.1:27017/admin?replicaSet=myReplicaSetName

Reference Link

https://www.mongodb.com/docs/manual/tutorial/convert-standalone-to-replica-set