NFS(5)							     Linux Programmer's Manual							    NFS(5)

NAME

       nfs - nfs fstab format and options

SYNOPSIS

       /etc/fstab

DESCRIPTION

       The  fstab  file contains information about which filesystems to mount where and with what options.  For NFS mounts, it contains the server
       name and exported server directory to mount from, the local directory that is the mount point, and the NFS specific  options  that  control
       the way the filesystem is mounted.

       Here is an example from an /etc/fstab file from an NFS mount.

       server:/usr/local/pub	/pub   nfs    rsize=8192,wsize=8192,timeo=14,intr

   Options
       rsize=n	      The number of bytes NFS uses when reading files from an NFS server.  The default value is dependent on the kernel, currently
		      1024 bytes.  (However, throughput is improved greatly by asking for rsize=8192.)

       wsize=n	      The number of bytes NFS uses when writing files to an NFS server.  The default value is dependent on the	kernel,  currently
		      1024 bytes.  (However, throughput is improved greatly by asking for wsize=8192.)

       timeo=n	      The value in tenths of a second before sending the first retransmission after an RPC timeout.  The default value is 7 tenths
		      of a second.  After the first timeout, the timeout is doubled after each successive timeout until a maximum  timeout  of	60
		      seconds  is  reached  or	the enough retransmissions have occured to cause a major timeout.  Then, if the filesystem is hard
		      mounted, each new timeout cascade restarts at twice the initial value of	the  previous  cascade,  again	doubling  at  each
		      retransmission.	The  maximum  timeout  is always 60 seconds.  Better overall performance may be achieved by increasing the
		      timeout when mounting on a busy network, to a slow server, or through several routers or gateways.

       retrans=n      The number of minor timeouts and retransmissions that must occur before a major timeout occurs.  The default is 3  timeouts.
		      When  a  major  timeout  occurs, the file operation is either aborted or a "server not responding" message is printed on the
		      console.

       acregmin=n     The minimum time in seconds that attributes of a regular file should be cached before requesting fresh  information  from  a
		      server.  The default is 3 seconds.

       acregmax=n     The  maximum  time  in  seconds  that  attributes of a regular file can be cached before requesting fresh information from a
		      server.  The default is 60 seconds.

       acdirmin=n     The minimum time in seconds that attributes of a directory should be cached  before  requesting  fresh  information  from  a
		      server.  The default is 30 seconds.

       acdirmax=n     The  maximum time in seconds that attributes of a directory can be cached before requesting fresh information from a server.
		      The default is 60 seconds.

       actimeo=n      Using actimeo sets all of acregmin, acregmax, acdirmin, and acdirmax to the same value.  There is no default value.

       retry=n	      The number of minutes to retry an NFS mount operation in the foreground or background before giving up.  The  default  value
		      is 10000 minutes, which is roughly one week.

       namlen=n       When  an	NFS  server does not support version two of the RPC mount protocol, this option can be used to specify the maximum
		      length of a filename that is supported on the remote filesystem.	This is used to support the POSIX pathconf functions.  The
		      default is 255 characters.

       port=n	      The  numeric value of the port to connect to the NFS server on.  If the port number is 0 (the default) then query the remote
		      host's portmapper for the port number to use.  If the remote host's NFS daemon is not registered with  its  portmapper,  the
		      standard NFS port number 2049 is used instead.

       mountport=n    The numeric value of the mountd port.

       mounthost=name The name of the host running mountd .

       mountprog=n    Use  an  alternate  RPC program number to contact the mount daemon on the remote host.  This option is useful for hosts that
		      can run multiple NFS servers.  The default value is 100005 which is the standard RPC mount daemon program number.

       mountvers=n    Use an alternate RPC version number to contact the mount daemon on the remote host.  This option is useful  for  hosts  that
		      can run multiple NFS servers.  The default value is version 1.

       nfsprog=n      Use  an alternate RPC program number to contact the NFS daemon on the remote host.  This option is useful for hosts that can
		      run multiple NFS servers.  The default value is 100003 which is the standard RPC NFS daemon program number.

       nfsvers=n      Use an alternate RPC version number to contact the NFS daemon on the remote host.  This option is useful for hosts that  can
		      run multiple NFS servers.  The default value is version 2.

       nolock	      Disable NFS locking. Do not start lockd.	This has to be used with some old NFS servers that don't support locking.

       bg	      If  the  first NFS mount attempt times out, retry the mount in the background.  After a mount operation is backgrounded, all
		      subsequent mounts on the same NFS server will be backgrounded immediately, without first attempting the  mount.	A  missing
		      mount point is treated as a timeout, to allow for nested NFS mounts.

       fg	      If  the  first NFS mount attempt times out, retry the mount in the foreground.  This is the complement of the bg option, and
		      also the default behavior.

       soft	      If an NFS file operation has a major timeout then report an I/O error to the calling program.  The default  is  to  continue
		      retrying NFS file operations indefinitely.

       hard	      If an NFS file operation has a major timeout then report "server not responding" on the console and continue retrying indef-
		      initely.	This is the default.

       intr	      If an NFS file operation has a major timeout and it is hard mounted, then allow signals to interupt the file  operation  and
		      cause it to return EINTR to the calling program.	The default is to not allow file operations to be interrupted.

       posix	      Mount  the  NFS filesystem using POSIX semantics.  This allows an NFS filesystem to properly support the POSIX pathconf com-
		      mand by querying the mount server for the maximum length of a filename.  To do this, the remote host  must  support  version
		      two of the RPC mount protocol.  Many NFS servers support only version one.

       nocto	      Suppress the retrieval of new attributes when creating a file.

       noac	      Disable all forms of attribute caching entirely.	This extracts a server performance penalty but it allows two different NFS
		      clients to get reasonable good results when both clients are actively writing to common filesystem on the server.

       tcp	      Mount the NFS filesystem using the TCP protocol instead of the default UDP protocol.  Many NFS servers only support UDP.

       udp	      Mount the NFS filesystem using the UDP protocol.	This is the default.

       All of the non-value options have corresponding nooption forms.	For example, nointr means don't allow file operations to be interrupted.

FILES

       /etc/fstab

SEE ALSO

       fstab(5), mount(8), umount(8), exports(5)

AUTHOR

       "Rick Sladkey" <jrs@world.std.com>

BUGS

       The posix, and nocto options are parsed by mount but currently are silently ignored.

       The tcp and namlen options are implemented but are not currently supported by the Linux kernel.

       The umount command should notify the server when an NFS filesystem is unmounted.

Linux 0.99							 20 November 1993							    NFS(5)