/etc/sudoers文件设置为允许用户在不输入该用户的密码的情况下使用所有命令

grep 666 /etc/sudoers
666     ALL=(ALL)    NOPASSWD:ALL
#666     ALL=(ALL)       ALL #sudo su - 时是需要输入666用户的密码，才能切换成root权限！！！！

$ who am i
666      pts/0        2017-04-26 11:15 
-bash-4.1$ sudo su -
[root@86 ~]# 
#免密码切到root权限
# who am i
666      pts/0        2017-04-26 11:15

grep root /etc/sudoers
## the root user, without needing the root password.
## Allow root to run any commands anywhere 
root    ALL=(ALL)     ALL