What is the of /etc/rd.d in the land where debian is king?

Here is what I am looking at:

"Now that your Internet Connection Sharing is setup it is recommend that you
combine all of the above commands into a script file so that it can be loaded
automatically every time your system boots up. To do this simply go to the
directory that contains some of the boot up commands, for example cd
/etc/rc.d/, in this directory you want to create a file say called
rc.firewall, and enter the following into the file:"

I do not have a /etc/rc.d, and since this guide was created for red hat I am
not surprised...

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Robert James Wultsch III
robert.wultsch@asu.edu
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