The best part: It is "Gold" as in , I have a perfect installation. Something goes wrong, and I got back to the LVM snapshot where it was pristine. This never happened, but sometimes, instead of uninstalling stuff I need to test, I just rollback any way. It runs wonderfully on one E3-1260L core and 512MB RAM.
This is exactly how Windows XP should be used these days, and it works perfectly fine. XP for Win32 functionality, the rest on Linux.
So, should any developer know this? That is debatable. I've had very competent developers who had next to no clue about how DNS works. They could do their job just fine with that. Me? Personally, I'm not up to snuff with the finer points of SQL queries and all the joins that exists and when it makes sense to create an index, etc. Could I find out? Most likely, but I haven't had the need to recently.
The problem is, that you are mapping your knowlegde to "what people must know". I used to do that too, and I probably still do often enough. The DNS example above didn't come from nowhere: I had the case, and I was really thinking "how could such a competent person not know this", but then this person could probably enlighten me about dozens of things I don't know well enough.
It all comes down to what you define as "general knowgledge" for a developer should be and that is highly subjective.
TL;DR Hiring people is hard. Especially, technical people.
"One lawyer can steal more than a hundred men with guns." -- The Godfather