MongoDB does not store data in tables, instead, it stores data in a “document” structure similar to JSON (in MongoDB called BSON).MongoDB is a NoSQL database that provides high performance, high availability, and automatic scaling. NoSQL database means that, unlike MySQL or PostgreSQL, it does not support SQL (Structured Query Language) to retrieve or manipulate the stored data.

Prerequisites

• CentOS 7
• Root privileges

Steps:

+Add the MongoDB repository.

+Installing MongoDB.

+Fix some MongoDB errors.

+Create an administrator user.

+Enable MongoDB authentication and Testing.

Connect to your CentOS 7 server with the ssh root account:

#ssh root@10.0.0.211

create new repository file ‘mongodb-org-3.2.repo’

#cd /etc/yum.repos.d/
#vi mongodb-org-3.2.repo

paste the followings

[mongodb-org-3.2]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/3.2/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-3.2.asc

save the file and and exit the editor.

Installing MongoDB

Run the command below and make sure mongodb repository is there.

#yum repolist

=====
repo id                                                                                               repo name                                                                                                                         status
!base/7/x86_64                                                                                        CentOS-7 - Base                                                                                                                   10,019
!epel/x86_64                                                                                          Extra Packages for Enterprise Linux 7 - x86_64                                                                                    12,985
!extras/7/x86_64                                                                                      CentOS-7 - Extras                                                                                                                    382
!jenkins                                                                                              Jenkins-stable                                                                                                                        86
!mongodb-org-3.2/7                                                                                    MongoDB Repository                                                                                                                   115
!updates/7/x86_64                                                                                     CentOS-7 - Updates  

Next, install MongoDB with the yum command.

#yum -y install mongodb-org

When the installation is finished, start MongoDB with this systemctl command:

systemctl start mongod

Check that MongoDB is running by checking that the port ‘27017’ is open.

#netstat -plntu

[root@syam ~]# netstat -plntu
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 127.0.0.1:27017         0.0.0.0:*               LISTEN      3110/mongod         
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      267/sshd            
tcp        0      0 0.0.0.0:1723            0.0.0.0:*               LISTEN      2889/pptpd          
tcp6       0      0 :::8080                 :::*                    LISTEN      1725/java           
tcp6       0      0 :::22                   :::*                    LISTEN      267/sshd            
udp6       0      0 :::33848                :::*                                1725/java           
udp6       0      0 :::5353                 :::*                                1725/java

And make sure the mongodb service is active.

[root@syam ~]# systemctl status mongod
● mongod.service - SYSV: Mongo is a scalable, document-oriented database.
   Loaded: loaded (/etc/rc.d/init.d/mongod; bad; vendor preset: disabled)
   Active: active (running) since Thu 2019-03-21 15:41:53 UTC; 1 day 12h ago
     Docs: man:systemd-sysv-generator(8)
  Process: 3077 ExecStop=/etc/rc.d/init.d/mongod stop (code=exited, status=0/SUCCESS)
  Process: 3095 ExecStart=/etc/rc.d/init.d/mongod start (code=exited, status=0/SUCCESS)
   CGroup: /system.slice/mongod.service
           └─3110 /usr/bin/mongod -f /etc/mongod.conf

Mar 21 15:41:53 syam systemd[1]: Stopped SYSV: Mongo is a scalable, document-oriented database..
Mar 21 15:41:53 syam systemd[1]: Starting SYSV: Mongo is a scalable, document-oriented database....
Mar 21 15:41:53 syam mongod[3095]: /etc/rc.d/init.d/mongod: line 67: ulimit: max locked memory: cannot modify limit: Operation not permitted
Mar 21 15:41:53 syam runuser[3106]: pam_unix(runuser:session): session opened for user mongod by (uid=0)
Mar 21 15:41:53 syam runuser[3106]: pam_unix(runuser:session): session closed for user mongod
Mar 21 15:41:53 syam systemd[1]: Started SYSV: Mongo is a scalable, document-oriented database..
Mar 21 15:41:53 syam mongod[3095]: Starting mongod: [  OK  ]

Fix a MongoDB Error

MongoDB is installed. Now we can access the mongodb shell by using the command below:

#mongo

You will probably see this error about ulimit configuration on the server.

** WARNING: soft rlimits too low. rlimits set to 4096 processes, 64000 files. Number of processes should be at least 32000…

the MongoDB database is running under the user ‘mongod’. Go to the ‘security’ directory and edit the ‘limits.conf’ configuration file.

#cd /etc/security/
#vi limits.conf

Paste new configuration below to the end of the file:

mongod soft nproc 64000
mongod hard nproc 64000
mongod soft nofile 64000
mongod hard nofile 64000

Save the limits.conf file.

#systemctl restart mongod
#mongo

[root@syam ~]# mongo
MongoDB shell version: 3.2.22
connecting to: test
> 

Type in the MongoDB query below to create the new administrator user:

[root@syam ~]# mongo
MongoDB shell version: 3.2.22
connecting to: test
> use admin
switched to db admin
> db.createUser(
...   {
...     user: "syam",
...     pwd: "syam123!@#",
...     roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]
...   }
... )
Successfully added user: {
	"user" : "syam",
	"roles" : [
		{
			"role" : "userAdminAnyDatabase",
			"db" : "admin"
		}
	]
}
> show users
{
	"_id" : "admin.admin",
	"user" : "admin",
	"db" : "admin",
	"roles" : [
		{
			"role" : "userAdminAnyDatabase",
			"db" : "admin"
		}
	]
}
{
	"_id" : "admin.syam",
	"user" : "syam",
	"db" : "admin",
	"roles" : [
		{
			"role" : "userAdminAnyDatabase",
			"db" : "admin"
		}
	]
}
> 

Enable User Authentication in MongoDB

Enable authentication for users to prevent that another user without sufficient privileges is able to see the data on the database.

On our CentOS 7 server, MongoDB is running under systemd with an init script in the ‘/etc/init.d/’ dirctory. We will edit that script to force the mongodb service to run with the ‘–auth’ option.

Go to the ‘/etc/init.d/’ directory and edit the “mongod” file:

#cd /etc/init.d/
vi mongod

In line 15 edit the following as follows,

OPTIONS=" --auth -f $CONFIGFILE"

save and exit editor

Reload the systemd service and restart MongoDB.

systemctl daemon-reload
systemctl restart mongod

Next, we have to test the configuration by logging into the mongo shell and switch to the admin database, then try to see the admin users.

mongo
 
use admin
show users

You will see an error about the unauthorised execution of the command in the database admin. Now we need to use the command ‘db.auth()’ for the authentication.

db.auth('admin', 'admin123')

Please see the mongo console details

[root@syam init.d]# mongo
MongoDB shell version: 3.2.22
connecting to: test
> use admin
switched to db admin
> show users
2019-03-23T04:07:59.196+0000 E QUERY    [thread1] Error: not authorized on admin to execute command { usersInfo: 1.0 } :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
DB.prototype.getUsers@src/mongo/shell/db.js:1523:1
shellHelper.show@src/mongo/shell/utils.js:764:9
shellHelper@src/mongo/shell/utils.js:671:15
@(shellhelp2):1:1

> db.auth('admin', 'admin123')
1
> show users
{
	"_id" : "admin.admin",
	"user" : "admin",
	"db" : "admin",
	"roles" : [
		{
			"role" : "userAdminAnyDatabase",
			"db" : "admin"
		}
	]
}
{
	"_id" : "admin.syam",
	"user" : "syam",
	"db" : "admin",
	"roles" : [
		{
			"role" : "userAdminAnyDatabase",
			"db" : "admin"
		}
	]
}
> 

Thats it…