> use admin 
switched to db admin 
> db.addUser('tank','test'); 

#bind_ip = 127.0.0.1   //注釋此行 
auth = true       //將此行前的注釋去掉

/etc/init.d/mongod 

iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 27017 -j ACCEPT