Virtual File System Overview

The virtual file system is an abstraction of a physical file system implementation. It provides a consistent interface to multiple file systems, both local and remote. This consistent interface allows the user to view the directory tree on the running system as a single entity even when the tree is made up of a number of diverse file system types.

The interface also allows the logical file system code in the kernel to operate without regard to the type of file system being accessed. For more information on the logical file system, see Logical File System Overview.

A virtual file system can also be viewed as a subset of the logical file system tree, that part belonging to a single file system implementation. A virtual file system can be physical (the instantiation of a physical file system), remote, or strictly logical. In the latter case, for example, a virtual file system need not actually be a true file system or entail any underlying physical storage device.

A virtual file system mount point grafts a virtual file system subtree onto the logical file system tree. This mount point ties together a mounted-over v-node (virtual node) and the root of the virtual file system subtree. A mounted-over, or stub, v-node points to a virtual file system, and the mounted VFS points to the v-node it is mounted over.