O mount bind deve fazer o truque:
mount --bind /some/where /else/where
A partir de esta excelente resposta :
What is a bind mount?
A bind mount is an alternate view of a directory tree. Classically, mounting creates a view of a storage device as a directory tree. A bind mount instead takes an existing directory tree and replicates it under a different point. The directories and files in the bind mount are the same as the original. Any modification on one side is immediately reflected on the other side, since the two views show the same data.