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mount_nfs(8)

NAME

     mount_nfs -- mount NFS file systems

SYNOPSIS

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

DESCRIPTION

     The mount_nfs utility calls the mount(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 imple-
     ments the mount protocol as described in RFC 1094, Appendix A and NFS:
     Network File System Version 3 Protocol Specification, Appendix I.

     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 -b and -R flags
     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 -i and -s flags.

     The options are:

     -2      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.

     -3      Use the NFS Version 3 protocol.

     -D      Set the ``dead server threshold'' to the specified number of
	     round trip timeout intervals before a ``server not responding''
	     message is displayed.

     -I      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.

     -L      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.

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

     -P      Use a reserved socket port number.  This flag is obsolete, 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
	     This is NOT supported by most non-BSD servers.)

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

     -a      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 product.

     -b      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 multi-
	     user operation.

     -c      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.

     -d      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 estimated timeout interval is too
	     short.

     -g      Set the maximum size of the group list for the credentials 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.

     -i      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.

     -l      Used with NQNFS and NFSV3 to specify that the ReaddirPlus RPC
	     should be used.  This option reduces RPC traffic for cases such
	     as ``ls -l'', but tends to flood the attribute and name caches
	     with prefetched entries.  Try this option and see whether perfor-
	     mance improves or degrades.  Probably most useful for client to
	     server network interconnects with a large bandwidth times delay
	     product.

     -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:

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

	     acregmin=<seconds>

	     acregmax=<seconds>
		     (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.

	     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.

	     Historic -o Options

	     Use of these options is deprecated, they are only mentioned here
	     for compatibility with historic versions of mount_nfs.

	     bg 	Same as -b.

	     conn	Same as not specifying -c.

	     dumbtimer	Same as -d.

	     intr	Same as -i.

	     lockd	Same as not specifying -L.

	     nfsv2	Same as -2.

	     nfsv3	Same as -3.

	     rdirplus	Same as -l.

	     mntudp	Same as -U.

	     resvport	Same as -P.

	     soft	Same as -s.

	     tcp	Same as -T.

     -r      Set the read data size to the specified value.  It should nor-
	     mally 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.)  See the -w
	     option as well.

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

     -t      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 overloaded 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 retrans-
	     mit rate but long response delay observed.  (Normally, the -d
	     do not support TCP mounts.

     -x      Set the retransmit timeout count for soft mounts to the specified
	     value.

SEE ALSO

     mount(2), unmount(2), fstab(5), mount(8), nfsd(8), nfsiod(8),
     showmount(8)

BUGS

     Due to the way that Sun RPC is implemented on top of UDP (unreliable
     datagram) transport, tuning such mounts is really a black art that can
     only be expected to have limited success.	For clients mounting servers
     that are not on the same LAN cable or that tend to be overloaded, TCP
     transport is strongly recommended, but unfortunately this is restricted
     to mostly 4.4BSD servers.

FreeBSD 5.4			 May 11, 2003			   FreeBSD 5.4

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