no valid sudoers sources found, quitting

执行sudo 。。。命令时报

sudo: /etc/sudoers is world writable
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin

解决办法，将/etc/sudoers的所有者，用户组，以及其他权限修改为 440
如下：chmod 440 /etc/sudoers