Hi.
For the topic of how components fit together, I preferred an O'Reilly graphic from Power Tools, rather than the onion for training in *nix -- see Figure 1.1 on page 8 (click
Browse Contents button on top of book image) at
Unix Power Tools, 3rd Edition-O'Reilly Media or see page 5 of the really long PDF
O'reilly Unix Unix Power Tools (5.6 Mb) PDF Ebook Download
(I'm not sure I can post it directly from O'Reilly or from the pdf for legal reasons, there may be other sources, and it's possible that O'Reilly might not mind, but I just don't know.)
It was better for me in the pedagogical sense, because I could start with the
User block on the whiteboard, and develop the diagram as the topic unfolded. Not much drawing skill was required, thankfully.
One could then discuss development, libraries, etc. -- very open-ended -- with simple block diagrams. Having the students do the drawing as we talked and answered questions helped them see and internalize the
big picture -- which is what we called that section ... cheers, drl