I didn't even know about tar or rsync until I started to use Linux, and I don't really see how else one get to the point where you need to know about them. And even symlinks are still in my mind as 'shortcuts but [...]' (even though the other way around is probably more accurate). Even as a dev, it's very possible to go through life without touching Linux.

If you've built any open source software ever, it's pretty hard not to know of tar, even if you don't know exactly what it is. I think it's reasonable to expect anyone interested in computers would be familiar with common compression tools, let alone a CS major.