350 lines
10 KiB
Groff
350 lines
10 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 May 11, 2003
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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 23NPTUbcdiLls
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.Op Fl D Ar deadthresh
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.Op Fl I Ar readdirsize
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.Op Fl R Ar retrycnt
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.Op Fl a Ar maxreadahead
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.Op Fl g Ar maxgroups
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.Op Fl o Ar options
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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 mount 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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.Fl b
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and
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.Fl R
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flags 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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.Fl i
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and
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.Fl s
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flags.
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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 (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 Fl 3
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Use the NFS Version 3 protocol.
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.It Fl D
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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 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 <= the read size for the mount.
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.It Fl L
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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 Fl N
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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 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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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 Fl R
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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 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 LAN cable as
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the client.
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(NB: This is NOT supported by most
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.No non- Ns Bx
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servers.)
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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 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 file system 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 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 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 EINTR 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 \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 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 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 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 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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.El
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.Pp
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.Sy Historic Fl o Sy Options
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.Pp
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Use of these options is deprecated, they are only mentioned here for
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compatibility with historic versions of
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.Nm .
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.Bl -tag -width ".Cm dumbtimer"
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.It Cm bg
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Same as
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.Fl b .
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.It Cm conn
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Same as not specifying
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.Fl c .
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.It Cm dumbtimer
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Same as
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.Fl d .
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.It Cm intr
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Same as
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.Fl i .
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.It Cm lockd
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Same as not specifying
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.Fl L .
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.It Cm nfsv2
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Same as
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.Fl 2 .
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.It Cm nfsv3
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Same as
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.Fl 3 .
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.It Cm rdirplus
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Same as
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.Fl l .
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.It Cm mntudp
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Same as
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.Fl U .
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.It Cm resvport
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Same as
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.Fl P .
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.It Cm soft
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Same as
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.Fl s .
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.It Cm tcp
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Same as
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.Fl T .
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.El
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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 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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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
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.Fl d
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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 Fl w
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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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.Fl r
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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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.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 SEE ALSO
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.Xr mount 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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.Sh BUGS
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Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram)
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transport, tuning such mounts is really a black art that can only be expected
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to have limited success.
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For clients mounting servers that are not on the same
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LAN cable or that tend to be overloaded,
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TCP transport is strongly recommended,
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but unfortunately this is restricted to mostly
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.Bx 4.4
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servers.
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