D:\programs\mongoDB\bin>mongo

 MongoDB shell version v3.4.6

 connecting to: mongodb://127.0.0.1:27017

 MongoDB server version: 3.4.

 > use admin

 switched to db admin　　

 >db.createUser(

    {

      user: "root",

      pwd: "rootpwd",

      roles: [ {role:"root", db:"admin"} ]

    }

 )

 > use admin  #1数据库切换至admin管理库

 switched to db admin

 > db.auth('root', 'rootpwd') #2验证root用户

 　

> use mydb  #3切换至业务库 在该库创建访问该库的用

>db.createUser(   # 创建用户

    {

      user: "test1",

      pwd: "",

      roles: [ {role:"dbOwner", db:"test1"} ]

    }

 )