[root@localhost zhangy]# mongo
MongoDB shell version: 2.4.6
connecting to: tank
> use admin          //切换到admin数据库
switched to db admin
> show collections;
system.indexes
system.users          //用户表
> db.system.users.find();   //用户表没有数据
> db.addUser('tank','test');  //添加一个管理员账号
{
  "user" : "tank",
  "readOnly" : false,
  "pwd" : "988432606980d0695e4f668f6bbc643a",
  "_id" : ObjectId("529e5d543b6a4608ac833429")
}

[root@localhost zhangy]# vim /etc/mongodb.conf      //将auth=true前面的注释拿掉
[root@localhost zhangy]# /etc/init.d/mongod restart   //重启生效

[root@localhost zhangy]# mongo
MongoDB shell version: 2.4.6
connecting to: tank
> show dbs;      //显示所有数据库失败，因为还没有认证
Wed Dec 4 06:39:50.925 listDatabases failed:{ "ok" : 0, "errmsg" : "unauthorized" } at src/mongo/shell/mongo.js:46
> db.auth('tank','test');  //认证失败，因为这个用户不属于tank这个数据库
Error: 18 { code: 18, ok: 0.0, errmsg: "auth fails" }
0
> use admin    //切换到admin数据库
switched to db admin
> db.auth('tank','test');  //在admin数据库认证成功
1
> use tank;      //切换到tank数据库
switched to db tank
> show collections;  //不会在提示没有权限了
contact
system.indexes
users

> use tank;
switched to db tank
> db.addUser('tank1','test');   //为tank数据库添加了一个可读写用户tank1
{
  "_id" : ObjectId("529e5f8474b4c660718a70f3"),
  "user" : "tank1",
  "readOnly" : false,
  "pwd" : "35dd47abff098f5b4f0b567db8edeac5"
}
> db.addUser('tank2','test',true); //为tank数据库添加了一个只读用户tank2
{
  "user" : "tank2",
  "readOnly" : true,
  "pwd" : "1792916c544d247538ded52e6df7b887",
  "_id" : ObjectId("529e67553992b24438d5e315")
}
> exit  //退出
bye
[root@localhost zhangy]# mongo
MongoDB shell version: 2.4.6
connecting to: tank
> db.auth('tank1','test');  //刚添加的用户可以登录。

$mongo = new Mongo();  

$db = $mongo->selectDB('tank');  //切换到tank数据库 

$db->authenticate("tank3", "test");  //认证

$users= $db->selectCollection("users"); //选取users表

$cursor = $users->find();  //读取数据

foreach ($cursor as $id => $value) {
  echo "$id: "; print_r($value); echo "<br>";
}

$mongo = new Mongo("mongodb://tank3:test@127.0.0.1:27017/tank");  //认证用户，这里的数据库，只启认证作用

$db = $mongo->selectDB('tank'); //选取数据库

$users= $db->selectCollection("users");

$cursor = $users->find();

foreach ($cursor as $id => $value) {
  echo "$id: "; print_r($value); echo "<br>";
}