Mongo Installation & Replica set step by Step

Mongo Installation

Step 1: Create a mongo repo file in /etc/yum.repos.d

[root@web01 yum.repos.d]# more mongodb.repo

[mongodb-org-3.6]

name=MongoDB Repository

baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/3.6/x86_64/

gpgcheck=1

enabled=1

gpgkey=https://www.mongodb.org/static/pgp/server-3.6.asc

Step 2: create mongod user & data directory

Useradd mongod

Passwd mongod

Mkdir -p /data/DATA

chown -R mongod:mongod /data/DATA

[Su to mongod]

Step 3: Create a Key File

openssl rand -base64 756 > mongo-keyfile

sudo mkdir /opt/mongo

sudo mv ~/mongo-keyfile /opt/mongo
sudo chmod 400 /opt/mongo/mongo-keyfile

sudo chown mongod:mongod /opt/mongo/mongo-keyfile

Step 4: Allow the port (iptables -Nl)

firewall-cmd --add-port=27017/tcp --permanent

firewall-cmd --reload

Step 3 : Intall Mongo

Yum install mongo

yum install -y mongodb-org

Step 4: Modify /etc/mongod.conf file

dbPath: /data/DATA

bindIp: 10.19.24.16

Step 4 : create sudoer file

vi /etc/sudoers.d/mongo
mongod ALL = (ALL) NOPASSWD: ALL

mongod ALL=(ALL) NOPASSWD: /usr/bin/systemctl start mongod

mongod ALL=(ALL) NOPASSWD: /usr/bin/systemctl stop mongod

mongod ALL=(ALL) NOPASSWD: /usr/bin/systemctl restart mongod

mongod ALL=(ALL) NOPASSWD: /usr/bin/systemctl status mongod

Step 5: Start mongo from mongod user

sudo systemctl start mongod

Step 6:

 mongo --port 27017 --host 10.19.24.16

use admin

db.createUser({user: "mongo-admin", pwd: "password125", roles:[{role: "root", db: "admin"}]})

Successfully added user: {

        "user" : "mongo-admin",

        "roles" : [

                {

                        "role" : "root",

                        "db" : "admin"

                }

        ]

}

Successfully added user: {

        "user" : "mongo-admin",

        "roles" : [

                {

                        "role" : "root",

                        "db" : "admin"

                }

        ]

}

Step 8:

Repeat everything same on node 2 from Step 1 to Step 5

Step 9: On node 1

Vi /etc/mongod.conf

security:

 keyFile: /opt/mongo/mongo-keyfile

replication:

 replSetName: rs0

sudo systemctl restart mongod

Step 10:

mongo --port 27017 -u mongo-admin -p password125 --authenticationDatabase admin --host 10.19.24.16

rs.initiate()

Rs.status()

Rs.add("10.19.24.17:27017")

 "errmsg" : "Quorum check failed because not enough voting nodes responded; required 2 but only the following 1 voting nodes responded10.19.24.17:27017; the following nodes did not respond affirmatively: 10.19.24.16:27017 failed with Authentication failed.",

rs.add( { host: "10.19.24.17:27017", priority: 0, votes: 0 } )

{

        "ok" : 1,

        "operationTime" : Timestamp(1540556102, 1),

        "$clusterTime" : {

                "clusterTime" : Timestamp(1540556102, 1),

                "signature" : {

                        "hash" : BinData(0,"drp3iE9HNq5ciPWaqHWedjHR9Vg="),

                        "keyId" : NumberLong("6616633136530849793")

                }

        }

}

In rs.status you can see some err " not reachable/healthy"

You need to add below to /etc/mongod.conf

security:

 keyFile: /opt/mongo/mongo-keyfile

replication:

 replSetName: rs0

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Testing if replication is working fine

rs0:PRIMARY> use ashishtest

switched to db ashishtest

rs0:PRIMARY> db

ashishtest

rs0:PRIMARY> db.movie.insert({"name":"Ashish Francis"})

WriteResult({ "nInserted" : 1 })

rs0:PRIMARY> db.movie.find()

{ "_id" : ObjectId("5bd3073ee3751e75430decfe"), "name" : "Ashish Francis" }

rs0:PRIMARY> show dbs;

admin       0.000GB

ashishtest  0.000GB

config      0.000GB

local       0.000GB

rs0:PRIMARY>

Now login to node to see if data replicated

 mongo --port 27017 -u mongo-admin -p password125 --authenticationDatabase admin --host 10.19.24.17

rs.slaveOk() -- so you can query slave node

rs0:SECONDARY> use ashishtest

switched to db ashishtest

rs0:SECONDARY> db.movie.find()

{ "_id" : ObjectId("5bd3073ee3751e75430decfe"), "name" : "Ashish Francis" }

rs0:SECONDARY>

We see the same data. Hence, replication is setup correctly.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

For application I created a database and a user to access that db

rs0:PRIMARY> use FIRSTDB

switched to db FIRSTDB

rs0:PRIMARY> db.createUser(

...    {

...      user: "firstuser",

...      pwd: "firstuser123",

...      roles: [{role: "userAdmin", db: "FIRSTDB"}]

...    }

... );

Successfully added user: {

        "user" : "firstuser",

        "roles" : [

                {

                        "role" : "userAdmin",

                        "db" : "FIRSTDB"

                }

        ]

}

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