404 lines
13 KiB
Groff
404 lines
13 KiB
Groff
.\" $NetBSD: mount_nfs.8,v 1.23 2003/08/07 10:04:29 agc 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 January 12, 1999
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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
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calls the
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.Xr mount 2
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system call to prepare and graft a remote nfs file system (rhost:path)
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on to the file system tree at the 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 NFS Version 2 protocol.
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.It Fl 3
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Use the NFS 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 NQNFS 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 DIRBLKSIZ that is \*[Le] the read size for the mount.
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.It Fl K
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Pass Kerberos authenticators to the server for client-to-server
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user-credential mapping.
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This requires that the kernel be built with the NFSKERB option.
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(Refer to the Internet-draft titled
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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 NQNFS 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 TCP transport instead of 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 NFS servers, especially not old ones, support this.
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.It Fl U
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Force the mount protocol to use UDP transport, even for TCP NFS mounts.
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(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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v3 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 UDP mount points, do not do a
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.Xr connect 2 .
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This flag is deprecated and connectionless UDP mounts are the default.
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.It Fl C
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For UDP mount points, do a
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.Xr connect 2 .
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Although this flag increases the efficiency of UDP mounts it cannot
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be used for servers that do not reply to requests from the
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standard NFS port number 2049, or for servers with multiple network
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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 UDP 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 NQNFS and NFSv3 to specify that the ReaddirPlus RPC should
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be used.
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This option reduces RPC traffic for cases such as
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.Dq "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 Kerberos 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 NFS Version 3 protocol
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to maintain cache consistency.
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This protocol version 2 revision to Not Quite Nfs (NQNFS)
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is only supported by this updated release of NFS code.
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It is not backwards compatible with the version 1 NQNFS protocol
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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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NFS system you will have to avoid this option until you have had
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an opportunity to upgrade the NFS 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.
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It should normally be a power of 2 greater than or equal to 1024.
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This should be used for UDP 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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.Fl w
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option as well.
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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 UDP 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.
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Ditto the comments with respect to the
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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 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 TCP 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 NFS 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 hardware can handle
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the larger packet sizes.
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The default size for version 2 is 8k when
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using UDP, 64k when using TCP.
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The default size for v3 is platform dependent:
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on i386, the default is 32k, for other platforms it is 8k.
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Values over
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32k are only supported for TCP, where 64k is the maximum.
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Any value
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over 32k is unlikely to get you more performance, unless you have
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a very fast network.
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.It
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If the hardware can not handle larger packet sizes, you may see low
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performance figures or even temporary hangups during NFS activity.
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This can especially happen with older ethernet cards.
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What happens
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is that either the buffer on the card on the client side is overflowing,
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or that similar events occur on the server, leading to a lot
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of dropped packets.
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In this case, decreasing the read and write size,
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using TCP, 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 NFS mounts
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because of a slow ethernet card, you can use
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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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in your kernel config file to avoid having do specify the
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sizes for all mounts.
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.It
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For connections that are not on the same LAN, and/or may experience
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packet loss, using TCP 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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A common mistake is that
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mountd 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.
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.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
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.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:
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.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 mount_nfs cannot resolve the name of the remote host.
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.Sh SEE ALSO
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.Xr mount 2 ,
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.Xr unmount 2 ,
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.Xr exports 5 ,
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.Xr fstab 5 ,
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.Xr mount 8 ,
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.Xr mountd 8 ,
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.Xr rpcinfo 8
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