Question: sudo /etc/sudoers is mode 0640 should be 0440?
Answer: If for whatever reason you change the permissions on your sudoers file you will get a similar error to "sudo: /etc/sudoers is mode 0640, should be 0440" whenever you try to run the sudo command. The problem is that because the permissions are wrong on the sudoers file, linux won't let you run the sudo command!