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MOUNT_NFS(8)		FreeBSD	System Manager's Manual		  MOUNT_NFS(8)

NAME
     mount_nfs -- mount	NFS file systems

SYNOPSIS
     mount_nfs [-23bcdiLlNPsTU]	[-a maxreadahead] [-D deadthresh]
	       [-g maxgroups] [-I readdirsize] [-o options] [-R	retrycnt]
	       [-r readsize] [-t timeout] [-w writesize] [-x retrans]
	       rhost:path node

DESCRIPTION
     The mount_nfs utility calls the nmount(2) system call to prepare and
     graft a remote NFS	file system (rhost:path) on to the file	system tree at
     the point node.  This command is normally executed	by mount(8).  It
     implements	the mount protocol as described	in RFC 1094, Appendix A	and
     NFS: Network File System Version 3	Protocol Specification,	Appendix I.

     If	the file system	type is	specified as ``oldnfs'', which implies this
     command is	run as ``mount_oldnfs'', then it forces	use of the old NFS
     client, which does	not support the	nfsv4 option.

     By	default, mount_nfs keeps retrying until	the mount succeeds.  This be-
     haviour is	intended for file systems listed in fstab(5) that are critical
     to	the boot process.  For non-critical file systems, the bg and retrycnt
     options provide mechanisms	to prevent the boot process from hanging if
     the server	is unavailable.

     If	the server becomes unresponsive	while an NFS file system is mounted,
     any new or	outstanding file operations on that file system	will hang
     uninterruptibly until the server comes back.  To modify this default be-
     haviour, see the intr and soft options.

     The options are:

     -o	     Options are specified with	a -o flag followed by a	comma sepa-
	     rated string of options.  See the mount(8)	man page for possible
	     options and their meanings.  The following	NFS specific options
	     are also available:

	     acregmin=<seconds>

	     acregmax=<seconds>

	     acdirmin=<seconds>

	     acdirmax=<seconds>
		     When attributes of	files are cached, a timeout calculated
		     to	determine whether a given cache	entry has expired.
		     These four	values determine the upper and lower bounds of
		     the timeouts for ``directory'' attributes and ``regular''
		     (ie: everything else).  The default values	are 3 -> 60
		     seconds for regular files,	and 30 -> 60 seconds for
		     directories.  The algorithm to calculate the timeout is
		     based on the age of the file.  The	older the file,	the
		     longer the	cache is considered valid, subject to the lim-
		     its above.

	     allgssname
		     This option can be	used along with	-o gssname to specify
		     that all operations should	use the	host-based initiator
		     credential.  This may be used for clients that run	system
		     daemons that need to access files on the NFSv4 mounted
		     volume.

	     bg	     If	an initial attempt to contact the server fails,	fork
		     off a child to keep trying	the mount in the background.
		     Useful for	fstab(5), where	the file system	mount is not
		     critical to multiuser operation.

	     deadthresh=<value>
		     Set the ``dead server threshold'' to the specified	number
		     of	round trip timeout intervals before a ``server not
		     responding'' message is displayed.

	     dumbtimer
		     Turn off the dynamic retransmit timeout estimator.	 This
		     may be useful for UDP mounts that exhibit high retry
		     rates, since it is	possible that the dynamically esti-
		     mated timeout interval is too short.

	     fg	     Same as not specifying bg.

	     gssname=<service-principal-name>
		     This option can be	used with the KerberosV	security fla-
		     vors for NFSv4 mounts to specify the
		     ``service-principal-name''	of a host-based	entry in the
		     default keytab file that is used for system operations.
		     It	allows the mount to be performed by ``root'' and
		     avoids problems with cached credentials for the system
		     operations	expiring.  The ``service-prinicpal-name''
		     should be specified without instance or domain and	is
		     typically ``host'', ``nfs'' or ``root''.

	     hard    Same as not specifying soft.

	     intr    Make the mount interruptible, which implies that file
		     system calls that are delayed due to an unresponsive
		     server will fail with EINTR when a	termination signal is
		     posted for	the process.

	     maxgroups=<value>
		     Set the maximum size of the group list for	the creden-
		     tials to the specified value.  This should	be used	for
		     mounts on old servers that	cannot handle a	group list
		     size of 16, as specified in RFC 1057.  Try	8, if users in
		     a lot of groups cannot get	response from the mount	point.

	     mntudp  Force the mount protocol to use UDP transport, even for
		     TCP NFS mounts.  (Necessary for some old BSD servers.)

	     nametimeo=<value>
		     Override the default of NFS_DEFAULT_NAMETIMEO for the
		     timeout (in seconds) for positive name cache entries.  If
		     this is set to 0 it disables positive name	caching	for
		     the mount point.

	     negnametimeo=<value>
		     Override the default of NFS_DEFAULT_NEGNAMETIMEO for the
		     timeout (in seconds) for negative name cache entries. If
		     this is set to 0 it disables negative name	caching	for
		     the mount point.

	     nfsv2   Use the NFS Version 2 protocol (the default is to try
		     version 3 first then version 2).  Note that NFS version 2
		     has a file	size limit of 2	gigabytes.

	     nfsv3   Use the NFS Version 3 protocol.

	     nfsv4   Use the NFS Version 4 protocol.  This option will force
		     the mount to use TCP transport.

	     minorversion=<value>
		     Override the default of 0 for the minor version of	the
		     NFS Version 4 protocol.  The only minor version currently
		     supported is 1.  This option is only meaningful when used
		     with the nfsv4 option.

	     pnfs    Enable support for	parallel NFS (pNFS) for	minor version
		     1 of the NFS Version 4 protocol.  This option is only
		     meaningful	when used with the minorversion	option.

	     noconn  For UDP mount points, do not do a connect(2).  This must
		     be	used if	the server does	not reply to requests from the
		     standard NFS port number 2049 or replies to requests
		     using a different IP address (which can occur if the
		     server is multi-homed).  Setting the
		     vfs.nfs.nfs_ip_paranoia sysctl to 0 will make this	option
		     the default.

	     nocto   Normally, NFS clients maintain the	close-to-open cache
		     coherency.	 This works by flushing	at close time and
		     checking at open time.  Checking at open time is imple-
		     mented by getting attributes from the server and purging
		     the data cache if they do not match attributes cached by
		     the client.

		     This option disables checking at open time.  It may
		     improve performance for read-only mounts, but should only
		     be	used if	the data on the	server changes rarely.	Be
		     sure to understand	the consequences before	enabling this
		     option.

	     noinet4, noinet6
		     Disables AF_INET or AF_INET6 connections.	Useful for
		     hosts that	have both an A record and an AAAA record for
		     the same name.

	     nolockd
		     Do	not forward fcntl(2) locks over	the wire.  All locks
		     will be local and not seen	by the server and likewise not
		     seen by other NFS clients.	 This removes the need to run
		     the rpcbind(8) service and	the rpc.statd(8) and
		     rpc.lockd(8) servers on the client.  Note that this
		     option will only be honored when performing the initial
		     mount, it will be silently	ignored	if used	while updating
		     the mount options.

	     principal
		     For the RPCSEC_GSS	security flavors, such as krb5,	krb5i
		     and krb5p,	this option sets the name of the host based
		     principal name expected by	the server. This option	over-
		     rides the default,	which will be ``nfs@<server-fqdn>''
		     and should	normally be sufficient.

	     noresvport
		     Do	not use	a reserved socket port number (see below).

	     port=<port_number>
		     Use specified port	number for NFS requests.  The default
		     is	to query the portmapper	for the	NFS port.

	     rdirplus
		     Used with NFSV3 to	specify	that the ReaddirPlus RPC
		     should be used.  For NFSV4, setting this option has a
		     similar effect, in	that it	will make the Readdir Opera-
		     tion get more attributes.	This option reduces RPC	traf-
		     fic for cases such	as ``ls	-l'', but tends	to flood the
		     attribute and name	caches with prefetched entries.	 Try
		     this option and see whether performance improves or
		     degrades.	Probably most useful for client	to server net-
		     work interconnects	with a large bandwidth times delay
		     product.

	     readahead=<value>
		     Set the read-ahead	count to the specified value.  This
		     may be in the range of 0 -	4, and determines how many
		     blocks will be read ahead when a large file is being read
		     sequentially.  Trying a value greater than	1 for this is
		     suggested for mounts with a large bandwidth * delay prod-
		     uct.

	     readdirsize=<value>
		     Set the readdir read size to the specified	value.	The
		     value should normally be a	multiple of DIRBLKSIZ that is
		     <=	the read size for the mount.

	     resvport
		     Use a reserved socket port	number.	 This flag is obso-
		     lete, and only retained for compatibility reasons.
		     Reserved port numbers are used by default now.  (For the
		     rare case where the client	has a trusted root account but
		     untrustworthy users and the network cables	are in secure
		     areas this	does help, but for normal desktop clients this
		     does not apply.)

	     retrans=<value>
		     Set the retransmit	timeout	count for soft mounts to the
		     specified value.

	     retrycnt=<count>
		     Set the mount retry count to the specified	value.	The
		     default is	a retry	count of zero, which means to keep
		     retrying forever.	There is a 60 second delay between
		     each attempt.

	     rsize=<value>
		     Set the read data size to the specified value.  It	should
		     normally be a power of 2 greater than or equal to 1024.
		     This should be used for UDP mounts	when the ``fragments
		     dropped due to timeout'' value is getting large while
		     actively using a mount point.  (Use netstat(1) with the
		     -s	option to see what the ``fragments dropped due to
		     timeout'' value is.)

	     sec=<flavor>
		     This option specifies what	security flavor	should be used
		     for the mount.  Currently,	they are:

		     krb5 -  Use KerberosV authentication
		     krb5i - Use KerberosV authentication and
			     apply integrity checksums to RPCs
		     krb5p - Use KerberosV authentication and
			     encrypt the RPC data
		     sys -   The default AUTH_SYS, which uses a
			     uid + gid list authenticator

	     soft    A soft mount, which implies that file system calls	will
		     fail after	retrycnt round trip timeout intervals.

	     tcp     Use TCP transport.	 This is the default option, as	it
		     provides for increased reliability	on both	LAN and	WAN
		     configurations compared to	UDP.  Some old NFS servers do
		     not support this method; UDP mounts may be	required for
		     interoperability.

	     timeout=<value>
		     Set the initial retransmit	timeout	to the specified
		     value.  May be useful for fine tuning UDP mounts over
		     internetworks with	high packet loss rates or an over-
		     loaded server.  Try increasing the	interval if nfsstat(1)
		     shows high	retransmit rates while the file	system is
		     active or reducing	the value if there is a	low retransmit
		     rate but long response delay observed.  (Normally,	the
		     dumbtimer option should be	specified when using this
		     option to manually	tune the timeout interval.)

	     udp     Use UDP transport.

	     wcommitsize=<value>
		     Set the maximum pending write commit size to the speci-
		     fied value.  This determines the maximum amount of	pend-
		     ing write data that the NFS client	is willing to cache
		     for each file.

	     wsize=<value>
		     Set the write data	size to	the specified value.  Ditto
		     the comments w.r.t. the rsize option, but using the
		     ``fragments dropped due to	timeout'' value	on the server
		     instead of	the client.  Note that both the	rsize and
		     wsize options should only be used as a last ditch effort
		     at	improving performance when mounting servers that do
		     not support TCP mounts.

COMPATIBILITY
     The following command line	flags are equivalent to	-o named options and
     are supported for compatibility with older	installations.

     -2	     Same as -o	nfsv2

     -3	     Same as -o	nfsv3

     -D	     Same as -o	deadthresh

     -I	     Same as -o	readdirsize=<value>

     -L	     Same as -o	nolockd

     -N	     Same as -o	noresvport

     -P	     Use a reserved socket port	number.	 This flag is obsolete,	and
	     only retained for compatibility reasons.  (For the	rare case
	     where the client has a trusted root account but untrustworthy
	     users and the network cables are in secure	areas this does	help,
	     but for normal desktop clients this does not apply.)

     -R	     Same as -o	retrycnt=<value>

     -T	     Same as -o	tcp

     -U	     Same as -o	mntudp

     -a	     Same as -o	readahead=<value>

     -b	     Same as -o	bg

     -c	     Same as -o	noconn

     -d	     Same as -o	dumbtimer

     -g	     Same as -o	maxgroups

     -i	     Same as -o	intr

     -l	     Same as -o	rdirplus

     -r	     Same as -o	rsize=<value>

     -s	     Same as -o	soft

     -t	     Same as -o	retransmit=<value>

     -w	     Same as -o	wsize=<value>

     -x	     Same as -o	retrans=<value>

SEE ALSO
     nmount(2),	unmount(2), nfsv4(4), fstab(5),	gssd(8), mount(8), nfsd(8),
     nfsiod(8),	showmount(8)

BUGS
     Since nfsv4 performs open/lock operations that have their ordering
     strictly enforced by the server, the options intr and soft	cannot be
     safely used.  hard	nfsv4 mounts are strongly recommended.

FreeBSD	10.1			 July 8, 2013			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | COMPATIBILITY | SEE ALSO | BUGS

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