NFS Services Administrator's Guide (B1031-90072, March 2011)

the server file tree. If you use the PUTROOTFH operation, the client can traverse the entire
file tree using the LOOKUP operation.
◦ Persistent
The persistent file handle is an assigned fixed value for the lifetime of the filesystem object
that it refers to. When the server creates the file handle for a filesystem object, the server
must accept the same file handle for the lifetime of the object. The persistent file handle
persists across server reboots and filesystem migrations.
◦ Volatile
Volatile file handles can be set to expire at a certain time. For example, they can be set
to expire during the filesystem migration. This file handle type is useful for servers that
cannot implement persistent file handles. However, the volatile file handles do not share
the same longevity characteristics of a persistent file handle, because these file handles
can become invalid or expire.
NOTE: HP-UX supports only persistent file handles. The client must know how to handle
persistent and volatile file handles. However, the server is not required to support both
types.
• Namespace Changes
The namespace describes the set of available files that are arranged in a hierarchy. When a
server shares files, it typically shares only a portion of its namespace. In NFSv4, the shared
namespace of the server forms a single hierarchy.
When a server shares separate filesystems as a disconnected portion of its namespace, the
server creates a pseudo filesystem to bridge the unshared portions of the namespace. This
enables a client, which has been enabled to traverse remote filesystems without having to
mount them, to access the shared points from a single common root.
The NFSv4 specification does not require a client to traverse the NFS server’s namespace.
For example, a server shares /opt/dce, /opt/hpsmh, and /doc/archives directories.
In this list, the shared list hierarchy is not connected. The /doc/archives directory is neither
a parent nor a child directory of /opt.
Figure 1 shows the server view of the shared directories.
Figure 1 Server View of the Shared Directories
If the administrator shares /, and /opt/dce. If the client mounts then the NFS client using
NFSv2 and NFSv3 can mount /and /opt/dce. Attempts to mount /opt will fail.
In NFSv4, the client can mount /, /opt and /opt/dce. If the client mounts /opt and lists
the contents of the directory, only the directory dce is seen. If you change directory (cd) to
dce, the contents of dce will be visible. HP-UX will allow the client to transparently cross this
filesystem boundary if the client has installed B.11.31.03 or greater.
• String Identifiers
NFSv4 represents users and groups in the following manner:
12 Introduction