sudo.d(directory):

Note also, that becasuse sudoers contents can vary widely, no attempt is made to add this 
directive to existing sudoers files on upgrade. Feel free to add the above directive to the 
end of your /etc/sudoers file to enabe this functionality for existing installations if you 
wish! Sudo versions older than the one in Debian 11(bullseye) require the directive will only 
support the old syntax #includedir, and the current sudo will happily accept both @includedir 
and #includedir

install

using root:

su - root

install:

apt install sudo

manual

chmod 640 /etc/sudoers
nano /etc/sudoers

在配置文件/etc/sudoers加入：

# User privilege specification
tdtc ALL=(ALL:ALL) ALL

把文件权限改为只读:

chmod 440 /etc/sudoers