How to enable Authentication in mongodb ?

Lets learn how to enable authentication in a local installation of mongodb.

Note: These steps are to be done on a linux OS

1. Start mongodb deamon
   $ sudo systemctl start mongod

2. Connect to mongodb using shell
   $ mongosh

3. Use admin database
   $ use admin

4. Create new user. Replace USER_NAME & USER_PASSWORD with the values that you want.
   $ db.createUser(
... {
... user: "USER_NAME",
... pwd: "USER_PASSWORD",
... roles: ["readWriteAnyDatabase"]
... }
... )

5. Exit shell
   $ exit

6. Modify the configuration file to enable authentication
   $ sudo nano /etc/mongod.conf

7. Uncomment security option and add authentication. The previous content will be
   #secutiry

8. There are 2 spaces before the authorization: enabled line. Save using Ctrl+X, confirm using Y and Enter. After updating configuration it will look like this.
   security:
authorization: enabled

9. Restart mongod
   $ sudo systemctl restart mongod

10. Verify the deamon is running and status is active
    $ sudo systemctl status mongod

11. Connect to mongoDb using shell.
    $ mongosh -u "USER_NAME" -p "USER_PASSWORD" --authenticationDatabase "admin"

If everything is correct it will connect to the default test database. To verify whether authentication is working use $ exit command and try to connect to mongoDb using
$ mongosh and list databases $ show dbs. It will return an error saying "MongoServerError: command listDatabases requires authentication".