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mount_nfs(1M)							 mount_nfs(1M)

       mount_nfs: mount, umount - mount and unmount remote NFS resources

       specific_options] resource mount_point


       This  manpage  describes	 only  the  NFS-specific  and  commands.   See
       mount(1M) for the description of the non-NFS commands.

       The utility attaches a named resource to the file system	 hierarchy  at
       the  pathname  location	mount_point,  which  must  already  exist.  If
       mount_point has any contents  prior  to	the  operation,	 the  contents
       remain hidden until the resource is once again unmounted.

       Only a superuser can mount file systems.

       The utility unmounts mounted file systems.

       Only a superuser can unmount file systems.

       resource can be of the form:

	    The	 host  can  be	the name of the NFS server host, or an IPv4 or
		 IPv6 address  string.	 As  IPv6  addresses  already  contain
		 colons, enclose host in a pair of square brackets when speci‐
		 fying an IPv6 address string.	Otherwise,  the	 first	occur‐
		 rence	of a colon can be interpreted as the separator between
		 the host name and path; for example:

		 See IPv6(7P).

		 pathname is the path name of  the  directory  on  the	server
		 being mounted.	 The path name is interpreted according to the
		 server's path name parsing rules, and the path	 name  is  not
		 necessarily  slash-separated.	 However, on most servers, the
		 path name is slash-separated.

	    Specify an NFS URL and follow the standard convention for
		 NFS URL as described in See the discussion of URL's  and  the
		 option under section below for a more detailed discussion.

	    A comma-separated list of:
		 or  See  the  discussion on under for a more detailed discus‐

	    A comma-separated list of:
		 hosts followed by a suffix.  See the discussion on under  for
		 a more detailed discussion.

   Options (mount)
       See mount(1M) for the description of the options.  Note that the option
       only accepts either or forces the use  of  NFS  Version	3  unless  the
       option is used.

       The options are as follows:

       Print debug messages to stderr.
	    This option is to be used by HP support engineers.

	    specific_options are NFS-specific only.

	    Set	 file  system  specific options according to a comma-separated
	    list with no intervening spaces.  are defined as follows:
	    Hold cached attributes for no more than n seconds after  directory
	    update.  The default value is

	    Hold cached attributes for at least
		   n seconds after directory update.  The default value is

	    Hold cached attributes for no more than
		   n seconds after file modification.  The default value is

	    Hold cached attributes for at least
		   n seconds after file modification.  The default value is

	    Set	   min	and  max  times for regular files and directories to n
		   seconds.  has no default; it sets and to the	 value	speci‐
		   fied by n.

	    If the first attempt fails, retry in the background
		   or in the foreground The default is

	    If	   is  specified,  then	 for the duration of the mount, forced
		   direct is used.  If the file system is mounted  using  data
		   is  transferred directly between client and server, with no
		   buffering on the client.  If the  file  system  is  mounted
		   using  data	is  buffered  on the client.  is a performance
		   option that is of benefit only  in  large  sequential  data
		   transfers.  The default behavior is

	    By default, the
		   GID associated with a newly created file obeys the System V
		   semantics; that is, the GID is set to the effective GID  of
		   the	calling process.  This behavior can be overridden on a
		   per-directory basis by setting the set-GID bit of the  par‐
		   ent	directory;  in	this  case, the GID of a newly created
		   file is set to the GID of the parent directory (see open(2)
		   and	mkdir(2)).   Files  created  on	 file systems that are
		   mounted with the option will obey BSD semantics independent
		   of  whether the set-GID bit of the parent directory is set;
		   that is, the GID is unconditionally inherited from that  of
		   the parent directory.

	    Continue to retry requests until the server responds
		   or give up and return an error The default value is

	    Allow  or  do not allow keyboard interrupts to kill a process that
		   is hung while waiting for a response on a hard-mounted file
		   system.   The  default is which allows clients to interrupt
		   applications that can be waiting for a remote mount.

	    By default, lock/unlock requests are sent to the server's
		   which enforces the requests.	 With  this  option  set,  the
		   lock/unlock	requests  are  not  sent to the remote and are
		   enforced locally.  These  local  locks  are	enforced  much
		   faster,  but	 if  other NFS clients access the same data on
		   the server, there is a risk	of  data  corruption.	Conse‐
		   quently,  this option must be used when only one NFS client
		   accesses the data on the server.

	    Suppress data and attribute caching.
		   The data caching that is suppressed	is  the	 write-behind.
		   The	local  page cache is still maintained, but data copied
		   into it is immediately written to the server.

	    Do not perform the normal close-to-open consistency.
		   When a file is closed, all modified	data  associated  with
		   the	file  is  flushed  to  the  server and not held on the
		   client.  When a file is opened the client sends  a  request
		   to  the server to validate the client's local caches.  This
		   behavior ensures a file's consistency across	 multiple  NFS
		   clients.   When  is	in effect, the client does not perform
		   the flush on close and the request for validation, allowing
		   the	possibility  of	 differences  among copies of the same
		   file as stored on multiple clients.

		   This option can be used in situations that  guarantee  that
		   accesses  to a specified file system are made from only one
		   client and only that client.	 Under such a  condition,  the
		   effect of can be a slight performance gain.

	    The server IP port number.
		   The	default	 is  If	 the  option  is specified, and if the
		   resource includes one or more NFS URLs, and if any  of  the
		   include  a number, then the number in the option and in the
		   URL must be the same.

		   semantics for the file system.  Requires a mount  NFS  Ver‐
		   sion 2 on the server.  See mountd(1M).

	    netid  is  a value of network_id field from entry in the file.  By
		   default, the transport protocol used for the NFS mount will
		   be  first available connection-oriented transport supported
		   on both the client and the server.  If  no  connection-ori‐
		   ented  transport is found, then the first available connec‐
		   tionless transport is used.	This default behavior  can  be
		   overridden with the option.

	    The	   option  forces  the use of the public file handle when con‐
		   necting to the NFS server.  The  resource  specified	 might
		   not	have  an  NFS  URL.  See the discussion on under for a
		   more detailed discussion.

	    Enable or prevent the command to check whether the	user  is  over
		   quota  on  this file system.	 If the file system has quotas
		   enabled on the server, quotas are still checked for	opera‐
		   tions on this file system.  See quota(1).

	    Disable the
		   functionality, which is used by default on an NFS Version 3
		   mount point,	 and  use  the	NFS  Version  2	 functionality
		   instead.   The  performance	of applications that read huge
		   directories over NFS will vary between NFS  Version	2  and
		   NFS Version 3 depending on the type of information that the
		   applications need.  The command will be  faster  using  NFS
		   Version  3  while the command will be faster using NFS Ver‐
		   sion 2 The option must be used on  a	 case  by  case	 basis
		   depending  upon  the application.  There is no effect on an
		   NFS Version 2 mount point.

	    Remount a read-only file system as read-write (using the

	    Set the number of NFS retransmissions to
		   n.  The default value  is  For  connection-oriented	trans‐
		   ports, this option has no effect because it is assumed that
		   the transport performs retransmissions on behalf of NFS.

	    The number of times to retry the
		   operation.  The default for the command is

		   is mounted read-write or read-only The default is

	    Set the read buffer size to
		   n bytes.  The default value is when using Version 3 of  the
		   NFS	protocol.   The	 default can be negotiated down if the
		   server prefers a smaller transfer size.  When using Version
		   2, the default value is

	    Set the security
		   mode for NFS transactions.  See nfssec(5) for the available
		   security mode options.

		   If is not specified, then the default action is to use over
		   NFS	Version 2 mounts, or to negotiate a security mode over
		   NFS Version 3 mounts.  NFS Version  3  mounts  negotiate  a
		   security  mode when the server returns an array of security
		   modes.  The client picks the first mode in the  array  that
		   is supported on the client.

		   Only one mode can be specified with the option.

	    This option is equivalent to the
		   option (Diffie-Hellman public key system).

	    Setuid execution is allowed
		   or disallowed The default is

	    Set the
		   NFS	timeout to n tenths of a second.  The default value is
		   tenths of  a	 second	 for  connectionless  transports,  and
		   tenths of a second for connection-oriented transports.

	    By default, the version of
		   NFS	protocol used between the client and the server is the
		   highest one available on both systems.  If the  NFS	server
		   does not support NFS Version 3 protocol, then the NFS mount
		   will use NFS Version 2 protocol.

		   To specify NFS Version 2, set NFS_version_number to be 2.

		   To specify NFS Version 3, set NFS_version_number to be 3.

		   If the option and are both specified, overrides the option.

	    Set the write buffer size to
		   n bytes.  The default value is when using Version 3 of  the
		   NFS	protocol.   The	 default can be negotiated down if the
		   server prefers a smaller transfer size.  When using Version
		   2, the default value is

       Prevent printing a warning message for unknown
	    specific_option.   If  the option is not specified, and an unknown
	    specific_option is encountered, the utility prints a warning  mes‐
	    sage and processes the next one.  The option prevents printing the
	    warning message.

       Overlay mount.
	    Allow the file system to be mounted over an existing mount	point,
	    making  the	 underlying  file  system inaccessible.	 If a mount is
	    attempted on a pre-existing mount point without setting this flag,
	    the mount will fail, producing the error

   Options (umount)
       The options are as follows:

       Attempt to unmount all NFS file systems described in

       Print debug messages to stderr.
	    This option is to be used by HP support engineers.

       Forcibly unmount a file system.
	    If this option is not specified, the utility does not allow a file
	    system to be unmounted if a file  on  the  file  system  is	 busy.
	    Using  the	option	can  cause  data loss for open files; programs
	    which access files after the file system has been  unmounted  will
	    get an error (EIO).

   Background versus Foreground
       File  systems  mounted with the option indicate that is to retry in the
       background  if  the  server's  mount  daemon  does  not	respond.   See
       mountd(1M).   retries  the  request  up	to  the count specified in the
       option.	Once the file system is mounted, each NFS request made in  the
       kernel  waits  tenths  of  a  second  for  a  response.	If no response
       arrives, the time-out is multiplied by and the request  is  retransmit‐
       ted.   When the number of retransmissions has reached the number speci‐
       fied in the option, a file system mounted with the  option  returns  an
       error on the request; one mounted with the option prints a warning mes‐
       sage and continues to retry the request.

   Hard versus Soft
       File systems that are mounted read-write	 or  that  contain  executable
       files  should  always  be  mounted with the option.  Applications using
       mounted file systems can incur unexpected I/O errors, file  corruption,
       unexpected  program  core  dumps, and delays in system reboot/shutdown.
       The option is not recommended.

   Authenticated requests
       The server can require authenticated NFS requests from the client.  The
       authentication  (Diffie-Hellman	public	key system) might be required.
       See nfssec(5).

   URLs and the public Option
       If the option is specified, or if the resource  includes	 an  NFS  URL,
       attempts	 to  connect to the server using the public file handle lookup
       protocol.  See If the server  supports  the  public  file  handle,  the
       attempt	is  successful;	 does not need to contact the server's and the
       daemons to get the port number of the server and the initial file  han‐
       dle of pathname, respectively.  See rpcbind(1M) and mountd(1M).	If the
       NFS client and server are separated by a firewall that allows all  out‐
       bound  connections  through  specific  ports,  such as then these ports
       enable NFS operations through the firewall.  The option and the NFS URL
       can be specified independently or together.  They interact as specified
       in the following matrix:

       │	      │		     Resource Style		  │
       │	      ├─────────────────────┬─────────────────────┤
       │	      │ host:pathname	    │ NFS URL		  │
       │public option │ Force  public  file │ Force  public  file │
       │	      │ handle	 and   fail │ handle   and   fail │
       │	      │ mount if  not  sup‐ │ mount if	not  sup‐ │
       │	      │ ported.	 Use Native │ ported.  Use Canon‐ │
       │	      │ paths.		    │ ical paths.	  │
       │Default	      │ Use MOUNT protocol. │ Try   public   file │
       │	      │			    │ handle with Canoni‐ │
       │	      │			    │ cal  paths.    Fall │
       │	      │			    │ back  to MOUNT pro‐ │
       │	      │			    │ tocol if	not  sup‐ │
       │	      │			    │ ported.		  │
       A  Native  path is a path name that is interpreted according to conven‐
       tions used on the native operating system of the NFS server.  A Canoni‐
       cal path is a path name that is interpreted according to the URL rules.
       See See for uses of Native and Canonical paths.

   Replicated File Systems and Failover
       resource can list multiple read-only file systems to be used to provide
       data.   These  file  systems should contain equivalent directory struc‐
       tures and identical files.  HP also recommends creating the file system
       directory  structure  with  a utility such as (see rdist(1)).  The file
       systems can be specified either with a comma-separated list of  entries
       and/or NFS URL entries, or with a comma-separated list of hosts, if all
       file system names are the same.	If multiple file systems are named and
       the  first server in the list is down, failover uses the next alternate
       server to access files.	If the read-only option is not chosen,	fails.
       Note that the option is always used for replicated servers.

   File Attributes
       To  improve NFS read performance, files and file attributes are cached.
       File modification times get updated whenever a write occurs.   However,
       file  access  times can be temporarily out-of-date until the cache gets

       The attribute cache retains file attributes on the client.   Attributes
       for  a file are assigned a time to be flushed.  If the file is modified
       before the flush time, then the flush time  is  extended	 by  the  time
       since  the  last	 modification  (under  the  assumption that files that
       changed recently are likely to change soon).  There is  a  minimum  and
       maximum	flush  time  extension	for regular files and for directories.
       Setting sets flush time to n seconds for both regular files and	direc‐

       Setting disables attribute caching on the client.  Then every reference
       to attributes is satisfied directly from the server though file data is
       still  cached.	Although  the  client is guaranteed to always have the
       latest  file  attributes	 from  the  server,  performance  is  affected
       adversely through additional latency, network load, and server load.

       Setting the option also disables attribute caching, but has the further
       effect of disabling client  write  caching.   Although  this  situation
       guarantees  that	 an application can write data directly to a server so
       that the data can be viewed immediately by other clients, a significant
       adverse	effect	on  client  write performance can occur.  Data written
       into memory-mapped file pages are not written directly to this  server.
       See mmap(2).

       returns the following values:

       Successful completion.

       An error occurred.
	      See the section.

       If  error  code	157 is returned, has reached the process thread limit.
       Increase the value of nkthread.	See nkthread(5) for more details.

   Example 1: Mounting an NFS File System
       To mount an NFS file system:

   Example 2: Mounting NFS File System Read-Only With No suid Privileges
       To mount an NFS file system read-only with no suid privileges:

   Example 3: Mounting NFS File System Over NFS Version 2 with the UDP	Trans‐
       To mount an NFS file system over NFS Version 2 with the UDP transport:

   Example 4: Mounting NFS File System Using An NFS URL
       To mount an NFS file system using an NFS URL (a canonical path):

   Example 5: Mounting With Forcing Use Of The Public File Handle
       To mount an NFS file system and force the use of the public file handle
       and an NFS URL (a canonical path) that has a  non  7-bit	 ASCII	escape

   Example 6: Mounting an NFS File System Using a Native Path
       To  mount an NFS file system using a native path (where the server uses
       colons as the component separator) and the public file handle:

   Example 7: Mounting a Replicated Set with Same Pathnames
       To mount a replicated set of NFS file systems with the same pathnames:

   Example 8: Mounting a Replicated Set with Different Pathnames
       To mount a replicated set of NFS file systems with different pathnames:

       If the directory on which a file system is to be mounted is a  symbolic
       link, the file system is mounted on the directory to which the symbolic
       link refers, rather than being mounted on  top  of  the	symbolic  link

       Table of mounted file systems

       Default distributed file system type

       Table of automatically mounted resources

       quota(1),  rdist(1),  fstyp(1M),	 lockd(1M),  mountall(1M), mountd(1M),
       statd(1M), mkdir(2), mmap(2), mount(2), open(2), umount(2),  mnttab(4),
       nfssec(5), quota(5), inet(7F), IPv6(7P).

       Callaghan, Brent, RFC 2054, October 1996.

       Callaghan, Brent, RFC 2224, October 1997.

       Berners-Lee, Masinter & McCahill , RFC 1738, December 1994.


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