/etc/sudoers is mode 0644 should be 0440

[test: /home] sudo mount /aaa

sudo: /etc/sudoers is mode 0644, should be 0440

sudo: no valid sudoers sources found, quitting

위와 깉에 어러가 날경우

root 권한으로 변경후

[test: /home] su

[root@/test] chmod 0440 /etc/sudoers

하면 된다.