run install by root, but always get error : "root is not in the sudoers file. This incident will be reported." why installer try to 'sudo'?

[#1]

I checked all files requiered FQDN in /etc/sysconfig/network, /etc/hosts.., and add root ALL=(ALL) NOPASSWD: ALL at end of sudoers file. why it always complain about root is not in sudoers file? and error only occurs when you do 'sudo' as root user.

is it possible a bug in installer?

[#2]

@Robin Dong Any updates?