after install run
sudo nano /etc/mongodb.conf
disable security # Security settings. #security: # authorization: enabled
the restart service and run with config
mongod --config /etc/mongodb.conf
other commands
db.createUser( { user: "admin", pwd: "admin", roles: [ { role: "root", db: "admin" } ] } );
db.createUser( { user: "mahmood", pwd: "12345", roles: ["readWrite"] } );
References
https://docs.mongodb.com/v3.0/reference/configuration-options/
http://stackoverflow.com/questions/23943651/mongodb-admin-user-not-authorized
http://stackoverflow.com/questions/35881662/mongodb-error-not-authorized-to-execute-command
https://docs.mongodb.com/manual/tutorial/enable-authentication/
http://stackoverflow.com/questions/23003391/how-do-i-add-an-admin-user-to-mongo-in-2-6