没有设root密码，sudoers文件权限怎么改回来

cyt@ubuntu:/etc$ ls -l|grep sudoer
-rwxrwxrwx  1 root    root      652 2011-06-02 21:45 sudoers
drwxr-xr-x  2 root    root     4096 2010-04-29 05:18 sudoers.d
cyt@ubuntu:/etc$ sudo chmod 0440 sudoers
sudo: /etc/sudoers is mode 0777, should be 0440
sudo: no valid sudoers sources found, quitting
cyt@ubuntu:/etc$ chmod 0440 sudoers
chmod: changing permissions of `sudoers': Operation not permitted
cyt@ubuntu:/etc$ su -
Password:
su: Authentication failure
cyt@ubuntu:/etc$

ubuntu没有root用户吧
只能用sudo
你试试sudo而不要用su -