Centos - why don't sudo rules for localhost work?

Question

local server

Greetings!
Because of what could this be?
the following rules do not work:
%groupname localhost=/sbin/shutdown -r now
, but the following rules work:
%groupname fullhostname=/sbin/shutdown -r now
fullhostname - machine name from /etc/hostname
At the same time, localhost is pinged.
OS - Centos 7.

Answer 1

From "man sudo":
Those. you need to write not "localhost", but what the "hostname" command says.