1.run install.sh file in all 3 servers. 

2.vim /etc/mongod.conf (in all 3 servers.)

	net:
		bindIp: 0.0.0.0
		
	replication:
	   replSetName: "my_rep"
	   
	#save file

3. get mongo shell -> mongo (only in one server)

	run below command only in one server. *** CHANGE DNS BEFORE RUN THIS.

	rs.initiate({_id : "my_rep",members: [{ _id: 0, host: "mongo1.facetone.lk:27017" },{ _id: 1, host: "mongo2.facetone.lk:27017" },{ _id: 2, host: "mongo3.facetone.lk:27017" }]})

4. check replication
	rs.status()
	rs.conf()
	
5. Convert one secondary as an arbiter
	stop service in the needed server
	remove from replica-set (in primary)
		rs.remove("sec_ip:port")
	remove data from data dir 
	create dir again & set permissions
	start service
	in primary
		rs.addArb("ser_ip:port")
	check rs.status()
	
6. add user

	db.createUser({user:"duo", pwd:"DuoS123", roles:[{role:"root", db:"admin"}]})

##################################################################################
#install.sh file
apt-get update
wget -qO - https://www.mongodb.org/static/pgp/server-4.0.asc | sudo apt-key add -

echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.0.list

apt-get update

sudo apt-get install -y mongodb-org=4.0.19 mongodb-org-server=4.0.19 mongodb-org-shell=4.0.19 mongodb-org-mongos=4.0.19 mongodb-org-tools=4.0.19

#stop updating mongod
echo "mongodb-org hold" | sudo dpkg --set-selections
echo "mongodb-org-server hold" | sudo dpkg --set-selections
echo "mongodb-org-shell hold" | sudo dpkg --set-selections
echo "mongodb-org-mongos hold" | sudo dpkg --set-selections
echo "mongodb-org-tools hold" | sudo dpkg --set-selections

systemctl start mongod

systemctl enable mongod

echo "Mongo 4.0.19 installed"

mongod -version

#end

#######
LINKS
https://docs.mongodb.com/v4.0/installation/