NFS Services Administrator's Guide (B.11.31.02) January 2008

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 is not visible. The client must specifically mount /opt/dce to see
the contents of dce. Future versions of HP-UX will allow the client to cross this filesystem
boundary on the server.
• String Identifiers
NFSv4 represents users and groups in the following manner:
users@domain
Or
group@domain
Where:
users specifies the string representation of the user
group specifies the string representation of the group
domain specifies a registered DNS domain or a sub-domain of a registered domain
However, UNIX systems use integers to represent users and groups in the underlying
filesystems stored on the disk. As a result, using string identifiers requires mapping of string
names to integers and back.
The nfsmapid daemon is used to map the owner and owner_group identification attributes
with the local user identification (UID) and group identification (GID) numbers, which are
used by both the NFSv4 server and the NFSv4 client.
On the NFS client, the nfsmapid daemon maps a numeric UID or a numeric GID to a string
representation. On the NFS server, it maps a string representation to a numeric UID or a
numeric GID.
For example, user casey with UID 121212 on an NFSv4 client whose fully qualified name
is system.anydomain.com is mapped to [e-mail]. The NFS client sends
the string representation, [e-mail], to the NFS server. The NFS server maps
the string representation, [e-mail], to the unique ID 121212.
The nfsmapid daemon uses the user and group entries in the /etc/nsswitch.conf file,
to determine which name service to use while converting strings and numerical values and
back.
For information on how to configure the nfsmapid daemon, see nfsmapid(1M).
• File Locking
File locking support is integrated with the NFSv4 protocol. NFSv4 introduces leases for lock
management.
When a server grants a lock to control the access of a file for a specific period of time, it is
called a lease. During the lease period, the server cannot grant conflicting access to another
client.
The lock lease interval can accept values higher than the cache consistency leases. As a result,
the client requires only a smaller number of refreshes. The lease ensures that the client does
not lose the locking state.
If a client refreshes a lock, all locks held by the client with that server are validated. This
reduces the number of lease refreshes by the client from one per lock to one per client for a
specific lease.
For information on configuring NFSv4 for the server, see “Configuring the NFSv4 Server Protocol
Version ” (page 24). For information on configuring NFSv4 for the client, see “Configuring the
NFSv4 Client Protocol Version” (page 39).
New Features in NFS 17