Each process has a port that is its root directory, just as it has a port that is its current working directory. The root directory port is inherited by fork/exec just like the current directory port is. This is how chroot works (the other piece of chroot is a filesystem RPC used to get a directory port that doesn't let /.. get out of the chosen "root" directory). As with chroot on Unix, a setuid program (called a secure exec in Hurdish) reverts to the global root directory port. So, modulo setuid, you can chroot your shell to a filesystem of your choice and the processes that descend from it will see that filesystem as the root for their lookups.
So, by setting a translator the implements the filesystem name space you want to see on ~/myroot, you can do "chroot ~/myroot" to go into that world.
