You don't really have to know the internals but I personally think you ought to know the abstactions themselves at the very least. To be more specific, you need

You don't really have to know the internals but I personally think you ought to know the abstactions themselves at the very least. To be more specific, you need not know say the internals of your compiler but you ought to know how compilers in general work. Same with protocols, filesystems, OS {vm,scheduler} ...etc.