Setup MongoDB replica set with three nodes

mongo_replica_config.sh

#!/bin/bash


######## Run this bash script on EACH replica set node to configure a Mongodb replica set #########

# HOWTO:
	# System recommendation : Ubuntu 16.04	
	# Download the script on each system of the replica set
	# Open in bash and make it executable with command: chmod +x mongo_replica_config.sh
	# Run with command: sudo ./mongo_replica_config.sh

# OTHER USEFUL SCRIPTS:
	# For MongoDB installation: https://gist.github.com/Maria-UET/1368387e2e72d2de96fc824919dad176
	# For initiating the MongoDB replica set after configuration: https://gist.github.com/Maria-UET/1368387e2e72d2de96fc824919dad176
 



# Replace with the ip addresses of all nodes in the replica set
IPS=("10.0.0.1" "10.0.0.2" "10.0.0.3")

# Replace with the hostnames of all nodes in the replica set 
HOSTS=("node1" "node2" "node3")


HOSTNAMES=("${IPS[0]} ${HOSTS[0]}" "${IPS[1]} ${HOSTS[1]}" "${IPS[2]} ${HOSTS[2]}")
ETC_HOSTS=/etc/hosts
REPL_SET="rs0"
BIND_IP=0.0.0.0


echo "Opening port 27017 for connection"
sudo iptables -A OUTPUT  -p tcp --source-port 27017 -m state --state ESTABLISHED -j ACCEPT
sudo iptables -A INPUT -p tcp --destination-port 27017 -m state --state NEW,ESTABLISHED -j ACCEPT


# Add the hostnames and ip addresses of all nodes in the replica set into /etc/hosts file
for i in ${!HOSTS[@]}
        do
            if [ -n "$(grep ${HOSTS[$i]} $ETC_HOSTS)" ]
                 then
                      echo "${HOSTS[$i]} already exists in $ETC_HOSTS" # check if the host is already present
            else
                 echo ${HOSTNAMES[$i]}>> /etc/hosts
            fi
        done


# Change the bingingIp of mongod server to allow binding to all three nodes. bindIp 0.0.0.0 allows binding to any ip, so do not use it without db authentication enabled 
echo "Changing bindingIP address to $BIND_IP"
sudo sed -i[bindIp] "s/bindIp: /bindIp: $BIND_IP #/g" /etc/mongod.conf


echo "Adding replica set configuration to the /etc/mongod.conf"
echo   "#replication config
replication:
  replSetName: $REPL_SET" >> /etc/mongod.conf


# Add the directory for server data if such directory doesnt already exist
echo "Creating directory /data/db"
sudo mkdir -p /data/db 


echo "Restarting the mongod server"
sudo systemctl stop mongod

sudo systemctl daemon-reload

#sudo systemctl start mongod
#echo `sudo systemctl restart mongod`


echo "Mongodb replica set configuration has been completed"
echo "Starting the mongod server with replica set $replSet with the following command:"
echo "sudo mongod --replSet $REPL_SET --bind_ip_all --fork --logpath /var/log/mongodb.log"
sudo mongod --replSet $REPL_SET --bind_ip $BIND_IP --fork --logpath /var/log/mongodb.log