use admin

db.createUser(
{
    user: "root",
    pwd: "abc123",
    roles: [
    {
        role: "root",
        db: "admin"
    }]
})

use project_db

db.createUser(
{
    user: "project_admin",
    pwd: "def456",
    roles: [
    {
        role: "dbOwner",
        db: "project_db"
    }]
})

mongo --username project_admin
      --password def456
      --authenticationDatabase project_db
    < "${path_to_db_build_script}"

db = connect("localhost:27017/project_db");
db.getSiblingDB("project_db").auth("project_admin", "def456");

db.auth("project_admin", "def456")

db.auth({ user: "project_admin", pwd: "def456" })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: fails })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: true })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: true, mechanism: "PLAIN" })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: fails, mechanism: "SCRAM-SHA-1" })

db.auth({ user: "project_admin", pwd: "def456", digestPassword: true, mechanism: "SCRAM-SHA-1" })

mongo admin -u root -p abc123

...
{
    "_id": "project_db.project_admin",
    "user": "project_admin",
    "db": "project_db",
    "credentials":
    {
        "SCRAM-SHA-1":
        {
            "iterationCount": 10000,
            "salt": "WnKFmGs3BTbmkbUWi0RPnA==",
            "storedKey": "EEIMqBEMUUOpoR3i3pgKz0iRumI=",
            "serverKey": "HsSOxujNODlKcRiEdi1zkj83MRo="
        }
    },
    "roles": [
    {
        "role": "dbOwner",
        "db": "project_db"
    }]
}
  ...

touch conn.js
chmod 600 conn.js
vim conn.js
# db = connect('localhost/mydb', 'myuser', 'pword');
vim myscript.js
# load('conn.js')
# db.coll.count()
mongo --nodb < myscript.js

var mongoose = require('mongoose');
var bcrypt = require('bcrypt');
var SALT_WORK_FACTOR = 10;
mongoose.connect('mongodb://localhost/project_db');

var db = mongoose.connection;

db.on('error', function(err){
    console.log('connection error', err);
});

db.once('open', function(){
    console.log('Connection to DB successful');
});

var Schema = mongoose.Schema;
var userSchema= new Schema({
    name:String,
    password:String
});

var User = mongoose.model('User', userSchema);

userSchema.pre('save', function(next){
    var user = this;
    if (!user.isModified('password')) return next();

    bcrypt.genSalt(SALT_WORK_FACTOR, function(err, salt){
        if(err) return next(err);

        bcrypt.hash(user.password, salt, function(err, hash){
            if(err) return next(err);

            user.password = hash;
            next();
        });
    });
});

var testSample = new  User({
    name: "admin",
   password: "password1234"
});

testSample.save(function(err, data){
    if(err) console.log(err);
    else console.log ('Sucess:' , data);
});