Description:

Unionfs is a Stackable Unification File System.
This project builds a stackable unification file system, which can
appear to merge the contents of several directories (branches), while
keeping their physical content separate. Unionfs is useful for unified
source tree management, merged contents of split CD-ROM, merged
separate software package directories, data grids, and more. Unionfs
allows any mix of read-only and read-write branches, as well as
insertion and deletion of branches anywhere in the fan-out. To
maintain unix semantics, Unionfs handles elimination of duplicates,
partial-error conditions, and more. Unionfs is part of the larger FiST
project.