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via nmount(), build up an iovec where each iovec member is an NFS mount option, and pass the iovec down to the kernel via nmount(). These options are then parsed in the kernel. This should make it easier to add new NFS mount options in future. Many, many thanks to Doug Rabson for taking my initial patches, and cleaning them up. In addition, Doug added a fallback_mount() function so that the newer mount_nfs program will work against older kernels, to facilitate upgrading/downgrading scenarios. Doug also re-wrote the mount_nfs.8 man page. Reviewed by: dfr
381 lines
11 KiB
Groff
381 lines
11 KiB
Groff
.\" 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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.\" 4. 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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.\" $FreeBSD$
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.\"
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.Dd February 11, 2008
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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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.Op Fl 234bcdiLlNPsTU
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.Op Fl a Ar maxreadahead
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.Op Fl D Ar deadthresh
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.Op Fl g Ar maxgroups
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.Op Fl I Ar readdirsize
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.Op Fl o Ar options
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.Op Fl R Ar retrycnt
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.Op Fl r Ar readsize
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.Op Fl t Ar timeout
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.Op Fl w Ar writesize
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.Op Fl x Ar retrans
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.Ar rhost : Ns Ar path node
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.Sh DESCRIPTION
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The
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.Nm
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utility calls the
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.Xr nmount 2
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system call to prepare and graft a remote NFS file system
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.Pq Ar rhost : Ns Ar 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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By default,
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.Nm
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keeps retrying until the mount succeeds.
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This behaviour is intended for file systems listed in
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.Xr fstab 5
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that are critical to the boot process.
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For non-critical file systems, the
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.Cm bg
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and
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.Cm retrycnt
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options provide mechanisms to prevent the boot process from hanging
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if the server is unavailable.
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.Pp
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If the server becomes unresponsive while an NFS file system is
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mounted, any new or outstanding file operations on that file system
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will hang uninterruptibly until the server comes back.
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To modify this default behaviour, see the
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.Cm intr
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and
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.Cm soft
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options.
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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 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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The following NFS specific options are also available:
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.Bl -tag -width indent
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.It Cm acregmin Ns = Ns Aq Ar seconds
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.It Cm acregmax Ns = Ns Aq Ar seconds
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.It Cm acdirmin Ns = Ns Aq Ar seconds
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.It Cm acdirmax Ns = Ns Aq Ar seconds
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When attributes of files are cached, a timeout calculated to determine
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whether a given cache entry has expired.
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These four values determine the upper and lower bounds of the timeouts for
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.Dq directory
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attributes and
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.Dq regular
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(ie: everything else).
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The default values are 3 -> 60 seconds
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for regular files, and 30 -> 60 seconds for directories.
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The algorithm to calculate the timeout is based on the age of the file.
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The older the file,
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the longer the cache is considered valid, subject to the limits above.
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.It Cm bg
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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 file system mount is not critical to multiuser operation.
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.It Cm deadthresh Ns = Ns Aq Ar value
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Set the
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.Dq "dead server threshold"
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to the specified number of round trip timeout intervals before a
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.Dq "server not responding"
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message is displayed.
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.It Cm dumbtimer
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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 Cm fg
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Same as not specifying
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.Cm bg .
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.It Cm hard
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Same as not specifying
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.Cm soft .
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.It Cm intr
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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 EINTR when a
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termination signal is posted for the process.
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.It Cm maxgroups Ns = Ns Aq Ar value
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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 Cm mntudp
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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 Cm nfsv2
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Use the NFS Version 2 protocol (the default is to try version 3 first
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then version 2).
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Note that NFS version 2 has a file size limit of 2 gigabytes.
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.It Cm nfsv3
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Use the NFS Version 3 protocol.
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.It Cm nfsv4
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Use the NFS Version 4 protocol.
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.It Cm noconn
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For UDP mount points, do not do a
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.Xr connect 2 .
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This must be used if the server does not reply to requests from the standard
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NFS port number 2049 or replies to requests using a different IP address
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(which can occur if the server is multi-homed).
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Setting the
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.Va vfs.nfs.nfs_ip_paranoia
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sysctl to 0 will make this option the default.
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.It Cm noinet4 , noinet6
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Disables
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.Dv AF_INET
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or
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.Dv AF_INET6
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connections.
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Useful for hosts that have
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both an A record and an AAAA record for the same name.
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.It Cm nolockd
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Do
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.Em not
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forward
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.Xr fcntl 2
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locks over the wire.
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All locks will be local and not seen by the server
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and likewise not seen by other NFS clients.
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This removes the need to run the
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.Xr rpcbind 8
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service and the
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.Xr rpc.statd 8
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and
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.Xr rpc.lockd 8
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servers on the client.
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Note that this option will only be honored when performing the
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initial mount, it will be silently ignored if used while updating
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the mount options.
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.It Cm noresvport
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Do
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.Em not
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use a reserved socket port number (see below).
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.It Cm port Ns = Ns Aq Ar port_number
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Use specified port number for NFS requests.
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The default is to query the portmapper for the NFS port.
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.It Cm rdirplus
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Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR 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
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most useful for client to server network interconnects with a large bandwidth
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times delay product.
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.It Cm readahead Ns = Ns Aq Ar value
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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 Cm readdirsize Ns = Ns Aq Ar value
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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 <= the read size for the mount.
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.It Cm resvport
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Use a reserved socket port number.
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This flag is obsolete, and only retained for compatibility reasons.
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Reserved port numbers are used by default now.
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(For the rare case where the client has a trusted root account
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but untrustworthy users and the network cables are in secure areas this does
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help, but for normal desktop clients this does not apply.)
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.It Cm retrans Ns = Ns Aq Ar value
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Set the retransmit timeout count for soft mounts to the specified value.
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.It Cm retrycnt Ns = Ns Aq Ar count
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Set the mount retry count to the specified value.
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The default is a retry count of zero, which means to keep retrying
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forever.
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There is a 60 second delay between each attempt.
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.It Cm rsize Ns = Ns Aq Ar value
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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 due to 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 due to timeout"
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value is.)
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.It Cm soft
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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 Cm tcp
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Use TCP transport.
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This is the default option, as it provides for increased reliability on both
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LAN and WAN configurations compared to UDP.
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Some old NFS servers do not support this method; UDP mounts may be required
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for interoperability.
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.It Cm timeout Ns = Ns Aq Ar value
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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
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.Cm dumbtimer
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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 Cm udp
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Use UDP transport.
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.It Cm wsize Ns = Ns Aq Ar value
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Set the write data size to the specified value.
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Ditto the comments w.r.t.\& the
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.Cm rsize
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option, but using the
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.Dq "fragments dropped due to 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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.Cm rsize
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and
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.Cm wsize
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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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.El
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.El
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.Sh COMPATIBILITY
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The following command line flags are equivalent to
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.Fl o
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named options and are supported for compatibility with older
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installations.
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.Bl -tag -width indent
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.It Fl 2
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Same as
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.Fl o Cm nfsv2
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.It Fl 3
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Same as
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.Fl o Cm nfsv3
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.It Fl 4
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Same as
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.Fl o Cm nfsv4
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.It Fl D
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Same as
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.Fl o Cm deadthresh
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.It Fl I
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Same as
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.Fl o Cm readdirsize Ns = Ns Aq Ar value
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.It Fl L
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Same as
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.Fl o Cm nolockd
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.It Fl N
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Same as
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.Fl o Cm noresvport
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.It Fl P
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Use a reserved socket port number.
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This flag is obsolete, and only retained for compatibility reasons.
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(For the rare case where the client has a trusted root account
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but untrustworthy users and the network cables are in secure areas this does
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help, but for normal desktop clients this does not apply.)
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.It Fl R
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Same as
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.Fl o Cm retrycnt Ns = Ns Aq Ar value
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.It Fl T
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Same as
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.Fl o Cm tcp
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.It Fl U
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Same as
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.Fl o Cm mntudp
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.It Fl a
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Same as
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.Fl o Cm readahead Ns = Ns Aq Ar value
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.It Fl b
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Same as
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.Fl o Cm bg
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.It Fl c
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Same as
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.Fl o Cm noconn
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.It Fl d
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Same as
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.Fl o Cm dumbtimer
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.It Fl g
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Same as
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.Fl o Cm maxgroups
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.It Fl i
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Same as
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.Fl o Cm intr
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.It Fl l
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Same as
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.Fl o Cm rdirplus
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.It Fl r
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Same as
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.Fl o Cm rsize Ns = Ns Aq Ar value
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.It Fl s
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Same as
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.Fl o Cm soft
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.It Fl t
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Same as
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.Fl o Cm retransmit Ns = Ns Aq Ar value
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.It Fl w
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Same as
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.Fl o Cm wsize Ns = Ns Aq Ar value
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.It Fl x
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Same as
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.Fl o Cm retrans Ns = Ns Aq Ar value
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.El
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.Sh SEE ALSO
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.Xr nmount 2 ,
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.Xr unmount 2 ,
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.Xr fstab 5 ,
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.Xr mount 8 ,
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.Xr nfsd 8 ,
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.Xr nfsiod 8 ,
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.Xr showmount 8
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