说明：
sudo命令的执行流程是: 当前用户转换到root, 然后以root身份执行命令, 执行完成后, 直接退回到当前用户.
需要注意的是: 执行sudo时输入的密码, 是当前用户的密码, 并非root密码

1、修改文件写权限
# ls -l /etc/sudoers
-r--r----- 1 root root 4042 Nov  4 15:05 /etc/sudoers
# chmod u+x /etc/sudoers
# vi /etc/sudoers
# ls -l /etc/sudoers

2、添加免密用户
vi  /etc/sudoers
## Allow root to run any commands anywhere
root    ALL=(ALL)       ALL
## add MySQL user 
mysql   ALL=(ALL)     NOPASSWD: ALL

3、sudo免密测试
[mysql@devdb01 ~]$ sudo ip addr
1: lo:  mtu 65536 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0:  mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:50:56:87:3b:bd brd ff:ff:ff:ff:ff:ff
    inet 1x2.55.3.xx/24 brd 196.55.3.255 scope global eth0
    inet6 fe80::250:56ff:fe87:3bbd/64 scope link 
       valid_lft forever preferred_lft forever
[mysql@devdb01 ~]$