nfs(7)                                                               nfs(7)




 NAME    [Toc]    [Back]
      nfs, NFS - network file system

 DESCRIPTION    [Toc]    [Back]
      The Network File System (NFS) allows a client node to perform
      transparent file access over the network.  By using NFS, a client node
      operates on files residing on a variety of servers and server
      architectures, and across a variety of operating systems.  File access
      calls on the client (such as read requests) are converted to NFS
      protocol requests and sent to the server system over the network.  The
      server receives the request, performs the actual file system
      operation, and sends a response back to the client.

      NFS operates in a stateless manner using remote procedure calls (RPC)
      built on top of an external data representation (XDR) protocol.  The
      RPC protocol enables version and authentication parameters to be
      exchanged for security over the network.

      A server grants access to a specific file system to clients by adding
      an entry for that file system to the server's /etc/exports file.

      A client gains access to that file system using the mount command to
      request a file handle for the file system (see mount(1M)).  (A file
      handle is the means by which NFS identifies remote files.) Once a
      client mounts the file system, the server issues a file handle to the
      client for each file (or directory) the client accesses.  If the file
      is removed on the server side, the file handle becomes stale
      (dissociated with a known file), and the server returns an error with
      errno set to [ESTALE].

      A server can also be a client with respect to file systems it has
      mounted over the network; however, its clients cannot directly access
      those file systems.  If a client attempts to mount a file system for
      which the server is an NFS client, the server returns with errno set
      to [EREMOTE].  The client must mount the file system directly from the
      server on which the file system resides.

      The user ID and group ID mappings must be the same between client and
      server.  However, the server maps UID 0 (the superuser) to UID -2
      before performing access checks for a client.  This process prevents
      gaining superuser privileges on remote file systems.

 RETURN VALUE    [Toc]    [Back]
      Generally, physical disk I/O errors detected at the server are
      returned to the client for action.  If the server is down or
      inaccessible, the client receives the message:

           NFS:  file server not responding: still trying.

      The client continues resending the request until it receives an
      acknowledgement from the server.  Therefore, the server can crash or



 Hewlett-Packard Company            - 1 -   HP-UX 11i Version 2: August 2003






 nfs(7)                                                               nfs(7)




      power down, and come back up without any special action required by
      the client.  The client process requesting the I/O will block, but
      remains sensitive to signals (unless mounted with the nointr option)
      until the server recovers.  However, if mounted with the soft option,
      the client process returns an error instead of waiting indefinitely.

 AUTHOR    [Toc]    [Back]
      nfs was developed by Sun Microsystems, Inc.

 SEE ALSO    [Toc]    [Back]
      exportfs(1M), mount(1M), mount_nfs(1M), nfsd(1M), mount(2), fstab(4),
      exports(4).


 Hewlett-Packard Company            - 2 -   HP-UX 11i Version 2: August 2003