This is some damn fine IT cartography, right here.
If you understand and are able to make appropriate use of every tool in those diagrams in solving comolex problems, there won’t be a GNU/Linux system (or any other, really, since this is the core of how computers work) you can’t learn to administer extremely quickly.
Masterful work, Mr. Gregg.
His site, incidentally, is so impressive that I renamed the post from its original title of “Excellent Concept-to-Command System Administration Maps” to its current title.
I’ve got some studying to do.