There are a couple of weird APIs like unshare(2) where it matters that you do things in the shell itself, not in a process spawned by a shell. (chdir(2) might be an even better example, come to think of it.) I once wrote a bash plugin for playing with unshare(2) specifically.<p>That said, unshare(1) now supports `-r` with `-U`, which was the thing I needed.