I actually hoard quite a bit of information for that, among other, contingencies. I've got engineering textbooks of all kinds, a book on the preservation of library books, books on metallurgy, a book on vacuum tube design, military survival manuals, medical textbooks, a book of constants and equations, chemistry textbooks, a Debian mirror and quite a bit more random stuff I've thought might be useful. It lives on several computers, plus some books in dead tree format. I have everything I'd need to devise a way to power any one of those computers without electricity from the grid essentially on demand. I probably ought to keep an archive of all that on optical disks, but if there's an EMP I'm pretty much screwed anyway.

I'm not a survivalist or something, I just started doing this on a whim because I was procrastinating on something. I honestly expect to never need most of it, but having my own Debian mirror is very convenient.