File System Name Space in NFS Version 4

NFS Version 4 servers create and maintain a pseudo file system that provides clients with seamless access to all exported objects on the server. Prior to NFS Version 4, the pseudo file system did not exist. Clients were forced to mount each shared server file system for access.

A pseudo file system is a structure that contains only directories and is created by the server. The pseudo file system permits a client to browse the hierarchy of exported file systems. Thus, the client's view of the pseudo file system is limited to paths that lead to exported file systems.

Previous versions of NFS did not permit a client to traverse server file systems without mounting each file system. However, in NFS Version 4, the server name space does the following:

• Restricts the client's file system view to directories that lead to server exports.

• Provides clients with seamless access to server exports without requiring the client to mount each underlying file system. However, different operating systems might require the client to mount each server file system.

Views of the Server File System and the Client File System in NFS Version 4

In the example shown in the figure, the client cannot see the payroll directory and the nfs4x directory because these directories are not exported and do not lead to exported directories. However, the local directory is visible to the client because local is an exported directory. The projects directory is visible to the client because projects leads to the exported directory, nfs4. Thus, portions of the server name space that are not explicitly exported are bridged with a pseudo file system that views only the exported directories and those directories that lead to server exports.