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