sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set

jason@jason-PC:~$ sudo 

sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set

and used to the root's passwd is unkonwn.

1.开机按shift或esc先进行recovery模式

2.选择root命令行模式

3.先执行

#mount -o remount,rw /

4. passwd root 

use this comand to modity the root's passwd

5.reboot the system

6.execute :su

and input the passwd you have set

7.now you can use: sudo