22e40d8402
but since I was here... Correct spelling of "Kerberos." Add RFC references. Reword some awkward english. Sprinkle mandoc macros throughout. Add white space to aid readability. Change date.
531 lines
14 KiB
Groff
531 lines
14 KiB
Groff
.\" $NetBSD: mount_nfs.8,v 1.25 2004/05/05 00:21:00 fair Exp $
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.\"
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.\" Copyright (c) 1992, 1993, 1994, 1995
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)mount_nfs.8 8.3 (Berkeley) 3/29/95
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.\"
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.Dd May 4, 2004
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.Dt MOUNT_NFS 8
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.Os
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.Sh NAME
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.Nm mount_nfs
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.Nd mount NFS file systems
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.Sh SYNOPSIS
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.Nm
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.Bk -words
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.Op Fl 23bcCdiKlpPqsTUX
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.Ek
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.Bk -words
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.Op Fl D Ar deadthresh
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.Ek
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.Bk -words
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.Op Fl I Ar readdirsize
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.Ek
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.Bk -words
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.Op Fl L Ar leaseterm
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.Ek
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.Bk -words
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.Op Fl R Ar retrycnt
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.Ek
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.Bk -words
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.Op Fl a Ar maxreadahead
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.Ek
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.Bk -words
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.Op Fl g Ar maxgroups
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.Ek
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.Bk -words
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.Op Fl m Ar realm
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.Ek
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.Bk -words
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.Op Fl o Ar options
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.Ek
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.Bk -words
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.Op Fl r Ar readsize
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.Ek
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.Bk -words
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.Op Fl t Ar timeout
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.Ek
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.Bk -words
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.Op Fl w Ar writesize
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.Ek
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.Bk -words
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.Op Fl x Ar retrans
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.Ek
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.Ar rhost:path node
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.Sh DESCRIPTION
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The
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.Nm
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command calls the
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.Xr mount 2
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system call to prepare and graft a remote
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.Tn NFS
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file system (rhost:path)
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on to the file system tree at the mount point
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.Ar node .
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This command is normally executed by
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.Xr mount 8 .
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It implements the mount protocol as described in RFC 1094, Appendix A and
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.%T "NFS: Network File System Version 3 Protocol Specification" ,
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Appendix I.
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.Pp
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The options are:
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.Bl -tag -width indent
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.It Fl 2
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Use the
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.Tn NFS
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Version 2 protocol.
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.It Fl 3
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Use the
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.Tn NFS
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Version 3 protocol.
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The default is to try version 3 first, and
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fall back to version 2 if the mount fails.
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.It Fl D
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Used with
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.Tn NQNFS
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to set the
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.Dq "dead server threshold"
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to the specified number of round trip timeout intervals.
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After a
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.Dq "dead server threshold"
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of retransmit timeouts,
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cached data for the unresponsive server is assumed to still be valid.
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Values may be set in the range of 1 - 9, with 9 referring to an
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.Dq "infinite dead threshold"
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(i.e. never assume cached data still valid).
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This option is not generally recommended and is really an experimental
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feature.
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.It Fl I
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Set the readdir read size to the specified value.
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The value should normally
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be a multiple of
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.Dv DIRBLKSIZ
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that is \*[Le] the read size for the mount.
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.It Fl K
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Pass
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.Tn Kerberos
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authenticators to the server for client-to-server user-credential mapping.
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This requires that the
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.Nx
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kernel be built with the
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.Dv NFSKERB
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.Xr option 4 .
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Refer to RFC 2695,
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.%T "Authentication Mechanisms for ONC RPC" ,
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for more information.
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.It Fl L
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Used with
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.Tn NQNFS
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to set the lease term to the specified number of seconds.
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Only use this argument for mounts with a large round trip delay.
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Values are normally in the 10-30 second range.
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.It Fl P
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Use a reserved socket port number.
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This is the default, and available
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for backwards compatibility purposes only.
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.It Fl R
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Set the retry count for doing the mount to the specified value.
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.It Fl T
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Use
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.Tn TCP
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transport instead of
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.Tn UDP .
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This is recommended for servers that are not on the same physical network as
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the client.
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Not all
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.Tn NFS
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servers, especially not old ones, support this.
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.It Fl U
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Force the mount protocol to use
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.Tn UDP
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transport, even for
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.Tn TCP
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.Tn NFS
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mounts.
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This is necessary for some old
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.Bx
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servers.
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.It Fl X
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Perform 32 \*[Lt]-\*[Gt] 64 bit directory cookie translation for version 3 mounts.
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This may be need in the case of a server using the upper 32 bits of
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version 3 directory cookies, and when you are running emulated binaries
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that access such a filesystem.
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Native
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.Nx
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binaries will never need this option.
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This option introduces some overhead.
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.It Fl a
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Set the read-ahead count to the specified value.
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This may be in the range of 0 - 4, and determines how many blocks
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will be read ahead when a large file is being read sequentially.
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Trying a value greater than 1 for this is suggested for
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mounts with a large bandwidth * delay product.
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.It Fl b
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If an initial attempt to contact the server fails, fork off a child to keep
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trying the mount in the background.
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Useful for
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.Xr fstab 5 ,
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where the filesystem mount is not critical to multiuser operation.
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.It Fl c
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For
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.Tn UDP
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mount points, do not do a
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.Xr connect 2 .
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This flag is deprecated and connectionless
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.Tn UDP
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mounts are the default.
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.It Fl C
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For
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.Tn UDP
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mount points, do a
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.Xr connect 2 .
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Although this flag increases the efficiency of
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.Tn UDP
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mounts it cannot
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be used for servers that do not reply to requests from the
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standard
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.Tn NFS
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port number 2049, or for servers with multiple network interfaces.
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In these cases if the socket is connected and the server
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replies from a different port number or a different network interface
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the client will get ICMP port unreachable and the mount will hang.
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.It Fl d
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Turn off the dynamic retransmit timeout estimator.
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This may be useful for
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.Tn UDP
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mounts that exhibit high retry rates,
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since it is possible that the dynamically estimated timeout interval is too
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short.
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.It Fl g
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Set the maximum size of the group list for the credentials to the
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specified value.
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This should be used for mounts on old servers that cannot handle a
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group list size of 16, as specified in RFC 1057.
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Try 8, if users in a lot of groups cannot get response from the mount
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point.
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.It Fl i
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Make the mount interruptible, which implies that file system calls that
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are delayed due to an unresponsive server will fail with
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.Er EINTR
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when a
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termination signal is posted for the process.
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.It Fl l
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Used with
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.Tn NQNFS
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and
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.Tn NFS
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Version 3 to specify that the
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.Fn ReaddirPlus
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.Tn RPC
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should be used.
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This option reduces
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.Tn RPC
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traffic for cases such as
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.Ic "ls -l" ,
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but tends to flood the attribute and name caches with prefetched entries.
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Try this option and see whether performance improves or degrades.
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Probably most useful for client to server network
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interconnects with a large bandwidth times delay product.
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.It Fl m
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Set the
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.Tn Kerberos
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realm to the string argument.
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Used with the
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.Fl K
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option for mounts to other realms.
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.It Fl o
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Options are specified with a
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.Fl o
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flag followed by a comma separated string of options.
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See the
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.Xr mount 8
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man page for possible options and their meanings.
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.It Fl p
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Do not use a reserved port number for RPCs.
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This option is provided only to be able to mimic the old
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default behavior of not using a reserved port, and should rarely be useful.
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.It Fl q
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Use the leasing extensions to the
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.Tn NFS
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Version 3 protocol
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to maintain cache consistency.
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This protocol version 2 revision to Not Quite
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.Tn NFS
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.Pq Tn NQNFS
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is only supported by this updated release of
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.Tn NFS
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code.
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It is not backwards compatible with the version 1
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.Tn NQNFS
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protocol that was part of the first release of
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.Bx 4.4 Lite .
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To interoperate with a first release
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.Bx 4.4 Lite
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.Tn NFS
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system you will have to avoid this option until you have had
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an opportunity to upgrade the
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.Tn NFS
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code to release 2 of
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.Bx 4.4 Lite
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on all your systems.
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.It Fl r
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Set the read data size to the specified value in bytes.
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It should normally be a power of 2 greater than or equal to 1024.
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.Pp
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This should be used for
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.Tn UDP
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mounts when the
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.Dq "fragments dropped after timeout"
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value is getting large while actively using a mount point.
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Use
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.Xr netstat 1
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with the
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.Fl s
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option to see what the
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.Dq "fragments dropped after timeout"
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value is.
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See the
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.Nm
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.Fl w
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option also.
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.It Fl s
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A soft mount, which implies that file system calls will fail
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after
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.Ar retrycnt
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round trip timeout intervals.
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.It Fl t
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Set the initial retransmit timeout to the specified value.
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May be useful for fine tuning
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.Tn UDP
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mounts over internetworks
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with high packet loss rates or an overloaded server.
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Try increasing the interval if
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.Xr nfsstat 1
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shows high retransmit rates while the file system is active or reducing the
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value if there is a low retransmit rate but long response delay observed.
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Normally, the -d option should be specified when using this option to manually
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tune the timeout
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interval.
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.It Fl w
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Set the write data size to the specified value in bytes.
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.Pp
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The same logic applies for use of this option as with the
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.Nm
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.Fl r
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option, but using the
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.Dq "fragments dropped after timeout"
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value on the
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.Tn NFS
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server instead of the client.
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Note that both the
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.Fl r
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and
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.Fl w
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options should only be used as a last ditch effort at improving performance
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when mounting servers that do not support
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.Tn TCP
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mounts.
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.It Fl x
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Set the retransmit timeout count for soft mounts to the specified value.
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.El
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.Sh EXAMPLES
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The simplest way to invoke
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.Nm
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is with a command like:
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.Pp
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.Dl "mount remotehost:/filesystem /localmountpoint
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or:
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.Dl "mount -t nfs remotehost:/filesystem /localmountpoint
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.Pp
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It is also possible to automatically mount filesystems at boot from your
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.Pa /etc/fstab
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by using a line like:
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.Pp
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.Dl "remotehost:/home /home nfs rw 0 0
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.Sh PERFORMANCE
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As can be derived from the comments accompanying the options, performance
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tuning of
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.Tn NFS
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can be a non-trivial task.
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Here are some common points
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to watch:
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.Bl -bullet -offset indent
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.It
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Increasing the read and write size with the
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.Fl r
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and
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.Fl w
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options respectively will increase throughput if the network
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interface can handle the larger packet sizes.
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.Pp
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The default size for
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.Tn NFS
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version 2 is 8K when
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using
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.Tn UDP ,
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64K when using
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.Tn TCP .
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.Pp
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The default size for
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.Tn NFS
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version 3 is platform dependent:
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on
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.Nx Ns /i386 ,
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the default is 32K, for other platforms it is 8K.
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Values over 32K are only supported for
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.Tn TCP ,
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where 64K is the maximum.
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.Pp
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Any value over 32K is unlikely to get you more performance, unless
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you have a very fast network.
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.It
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If the network interface cannot handle larger packet sizes or a
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long train of back to back packets, you may see low performance
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figures or even temporary hangups during
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.Tn NFS
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activity.
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.Pp
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This can especially happen with older
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.Tn Ethernet
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network interfaces.
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What happens is that either the receive buffer on the network
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interface on the client side is overflowing, or that similar events
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occur on the server, leading to a lot of dropped packets.
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.Pp
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In this case, decreasing the read and write size, using
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.Tn TCP ,
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or a combination of both will usually lead to better throughput.
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Should you need to decrease the read and write size for all your
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.Tn NFS
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mounts because of a slow
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.Tn Ethernet
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network interface
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.Pq e.g. a USB 1.1 to 10/100 Tn Ethernet network interface ,
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you can use
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.Pp
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.Bl -ohang -compact
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.It Cd options NFS_RSIZE=value
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.It Cd options NFS_WSIZE=value
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.El
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.Pp
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in your kernel
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.Xr config 8
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file to avoid having do specify the sizes for all mounts.
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.It
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For connections that are not on the same
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.Tn LAN ,
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and/or may experience packet loss, using
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.Tn TCP
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is strongly recommended.
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.El
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.Sh ERRORS
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|
Some common problems with
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.Nm
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|
can be difficult for first time users to understand.
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|
.Pp
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.Dl "mount_nfs: can't access /foo: Permission denied
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.Pp
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This message means that the remote host, is either not exporting
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the filesystem you requested, or is not exporting it to your host.
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|
If you believe the remote host is indeed exporting a filesystem to you,
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|
make sure the
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.Xr exports 5
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file is exporting the proper directories.
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.Pp
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A common mistake is that
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.Xr mountd 8
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will not export a filesystem with the
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.Fl alldirs
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option, unless it
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|
is a mount point on the exporting host.
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|
It is not possible to remotely
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mount a subdirectory of an exported mount, unless it is exported with the
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.Fl alldirs
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option.
|
|
.Pp
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|
The following error:
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|
.Pp
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|
.Dl "NFS Portmap: RPC: Program not registered
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.Pp
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|
means that the remote host is not running
|
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.Xr mountd 8 .
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|
The program
|
|
.Xr rpcinfo 8
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|
can be used to determine if the remote host is running nfsd, and mountd by issuing
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the command:
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|
.Pp
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|
.Dl rpcinfo -p remotehostname
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|
.Pp
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|
If the remote host is running nfsd, and mountd, it would display:
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|
.Pp
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|
.Dl "100005 3 udp 719 mountd
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|
.Dl "100005 1 tcp 720 mountd
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.Dl "100005 3 tcp 720 mountd
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|
.Dl "100003 2 udp 2049 nfs
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.Dl "100003 3 udp 2049 nfs
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.Dl "100003 2 tcp 2049 nfs
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.Dl "100003 3 tcp 2049 nfs
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.Pp
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|
The error:
|
|
.Pp
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|
.Dl "mount_nfs: can't get net id for host
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.Pp
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|
indicates that
|
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.Nm
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|
cannot resolve the name of the remote host.
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|
.Sh SEE ALSO
|
|
.Xr nfsstat 1 ,
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|
.Xr mount 2 ,
|
|
.Xr unmount 2 ,
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|
.Xr options 4 ,
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|
.Xr exports 5 ,
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|
.Xr fstab 5 ,
|
|
.Xr mount 8 ,
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.Xr mountd 8 ,
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.Xr rpcinfo 8
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|
.Rs
|
|
.%R RFC 1094
|
|
.%D March 1989
|
|
.%T "NFS: Network File System Protocol specification"
|
|
.Re
|
|
.Rs
|
|
.%R RFC 2623
|
|
.%D June 1999
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|
.%T "NFS Version 2 and Version 3 Security Issues and the NFS Protocol's Use of RPCSEC_GCC and Kerberos V5"
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|
.Re
|
|
.Rs
|
|
.%R RFC 2624
|
|
.%D June 1999
|
|
.%T "NFS Version 4 Design Considerations"
|
|
.Re
|
|
.Rs
|
|
.%R RFC 2695
|
|
.%D September 1999
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|
.%T "Authentication Mechanisms for ONC RPC"
|
|
.Re
|