How to enable password authentication in MongoDB 3.x

Create one admin user in the special db admin like this:

  $ mongo
  > use admin
  > db.createUser({user:"root-username",pwd:"root-password", roles:[{role:"root",db:"admin"}]})
  > exit

Now open /ect/mongod.conf in your favorite text editor and enable authentication by adding this to it:

security:
   authorization: enabled

Now restart your mongodb sudo service mongod restart.