428 lines
12 KiB
Groff
428 lines
12 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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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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.\" @(#)exports.5 8.3 (Berkeley) 3/29/95
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.\" $FreeBSD$
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.\"
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.Dd June 30, 2008
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.Dt EXPORTS 5
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.Os
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.Sh NAME
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.Nm exports
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.Nd define remote mount points for
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.Tn NFS
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mount requests
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.Sh SYNOPSIS
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.Nm
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.Sh DESCRIPTION
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The
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.Nm
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file specifies remote mount points for the
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.Tn NFS
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mount protocol per the
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.Tn NFS
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server specification; see
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.%T "Network File System Protocol Specification" ,
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RFC1094, Appendix A and
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.%T "NFS: Network File System Version 3 Specification" ,
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Appendix I.
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.Pp
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Each line in the file
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(other than comment lines that begin with a #)
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specifies the mount point(s) and export flags within one local server
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file system for one or more hosts.
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A long line may be split over several lines by ending all but the
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last line with a backslash
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.Pq Ql \e .
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A host may be specified only once for each local file system on the
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server and there may be only one default entry for each server
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file system that applies to all other hosts.
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The latter exports the file system to the
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.Dq world
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and should
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be used only when the file system contains public information.
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.Pp
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In a mount entry,
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the first field(s) specify the directory path(s) within a server file system
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that can be mounted on by the corresponding client(s).
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There are two forms of this specification.
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The first is to list all mount points as absolute
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directory paths separated by whitespace.
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The second is to specify the pathname of the root of the file system
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followed by the
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.Fl alldirs
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flag;
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this form allows the host(s) to mount at any point within the file system,
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including regular files if the
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.Fl r
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option is used on
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.Xr mountd 8 .
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The pathnames must not have any symbolic links in them and should not have
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any
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.Dq Pa \&.
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or
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.Dq Pa ..
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components.
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Mount points for a file system may appear on multiple lines each with
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different sets of hosts and export options.
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.Pp
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The second component of a line specifies how the file system is to be
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exported to the host set.
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The option flags specify whether the file system
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is exported read-only or read-write and how the client UID is mapped to
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user credentials on the server.
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.Pp
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Export options are specified as follows:
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.Pp
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.Sm off
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.Fl maproot Li = Sy user
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.Sm on
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The credential of the specified user is used for remote access by root.
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The credential includes all the groups to which the user is a member
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on the local machine (see
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.Xr id 1 ) .
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The user may be specified by name or number.
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.Pp
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.Sm off
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.Fl maproot Li = Sy user:group1:group2:...
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.Sm on
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The colon separated list is used to specify the precise credential
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to be used for remote access by root.
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The elements of the list may be either names or numbers.
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Note that user: should be used to distinguish a credential containing
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no groups from a complete credential for that user.
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.Pp
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.Sm off
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.Fl mapall Li = Sy user
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.Sm on
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or
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.Sm off
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.Fl mapall Li = Sy user:group1:group2:...
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.Sm on
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specifies a mapping for all client UIDs (including root)
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using the same semantics as
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.Fl maproot .
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.Pp
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The option
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.Fl r
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is a synonym for
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.Fl maproot
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in an effort to be backward compatible with older export file formats.
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.Pp
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In the absence of
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.Fl maproot
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and
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.Fl mapall
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options, remote accesses by root will result in using a credential of -2:-2.
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All other users will be mapped to their remote credential.
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If a
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.Fl maproot
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option is given,
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remote access by root will be mapped to that credential instead of -2:-2.
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If a
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.Fl mapall
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option is given,
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all users (including root) will be mapped to that credential in
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place of their own.
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.Pp
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The
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.Fl ro
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option specifies that the file system should be exported read-only
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(default read/write).
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The option
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.Fl o
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is a synonym for
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.Fl ro
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in an effort to be backward compatible with older export file formats.
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.Pp
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.Tn WebNFS
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exports strictly according to the spec (RFC 2054 and RFC 2055) can
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be done with the
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.Fl public
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flag.
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However, this flag in itself allows r/w access to all files in
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the file system, not requiring reserved ports and not remapping UIDs.
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It
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is only provided to conform to the spec, and should normally not be used.
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For a
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.Tn WebNFS
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export,
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use the
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.Fl webnfs
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flag, which implies
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.Fl public ,
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.Sm off
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.Fl mapall No = Sy nobody
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.Sm on
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and
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.Fl ro .
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Note that only one file system can be
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.Tn WebNFS
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exported on a server.
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.Pp
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A
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.Sm off
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.Fl index No = Pa file
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.Sm on
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option can be used to specify a file whose handle will be returned if
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a directory is looked up using the public filehandle
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.Pq Tn WebNFS .
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This is to mimic the behavior of URLs.
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If no
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.Fl index
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option is specified, a directory filehandle will be returned as usual.
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The
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.Fl index
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option only makes sense in combination with the
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.Fl public
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or
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.Fl webnfs
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flags.
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.Pp
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Specifying the
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.Fl quiet
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option will inhibit some of the syslog diagnostics for bad lines in
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.Pa /etc/exports .
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This can be useful to avoid annoying error messages for known possible
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problems (see
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.Sx EXAMPLES
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below).
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.Pp
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The third component of a line specifies the host set to which the line applies.
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The set may be specified in three ways.
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The first way is to list the host name(s) separated by white space.
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(Standard Internet
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.Dq dot
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addresses may be used in place of names.)
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The second way is to specify a
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.Dq netgroup
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as defined in the
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.Pa netgroup
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file (see
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.Xr netgroup 5 ) .
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The third way is to specify an Internet subnetwork using a network and
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network mask that is defined as the set of all hosts with addresses within
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the subnetwork.
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This latter approach requires less overhead within the
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kernel and is recommended for cases where the export line refers to a
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large number of clients within an administrative subnet.
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.Pp
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The first two cases are specified by simply listing the name(s) separated
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by whitespace.
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All names are checked to see if they are
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.Dq netgroup
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names
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first and are assumed to be hostnames otherwise.
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Using the full domain specification for a hostname can normally
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circumvent the problem of a host that has the same name as a netgroup.
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The third case is specified by the flag
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.Sm off
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.Fl network Li = Sy netname Op Li / Ar prefixlength
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.Sm on
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and optionally
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.Sm off
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.Fl mask No = Sy netmask .
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.Sm on
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The netmask may be specified either by attaching a
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.Ar prefixlength
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to the
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.Fl network
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option, or by using a separate
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.Fl mask
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option.
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If the mask is not specified, it will default to the mask for that network
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class (A, B or C; see
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.Xr inet 4 ) .
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See the
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.Sx EXAMPLES
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section below.
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.Pp
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Scoped IPv6 address must carry scope identifier as documented in
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.Xr inet6 4 .
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For example,
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.Dq Li fe80::%re2/10
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is used to specify
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.Li fe80::/10
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on
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.Li re2
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interface.
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.Pp
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The
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.Xr mountd 8
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utility can be made to re-read the
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.Nm
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file by sending it a hangup signal as follows:
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.Bd -literal -offset indent
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/etc/rc.d/mountd reload
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.Ed
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.Pp
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After sending the
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.Dv SIGHUP ,
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check the
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.Xr syslogd 8
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output to see whether
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.Xr mountd 8
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logged any parsing errors in the
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.Nm
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file.
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.Sh FILES
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.Bl -tag -width /etc/exports -compact
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.It Pa /etc/exports
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the default remote mount-point file
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.El
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.Sh EXAMPLES
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.Bd -literal -offset indent
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/usr /usr/local -maproot=0:10 friends
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/usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16
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/usr -ro -mapall=nobody
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/u -maproot=bin: -network 131.104.48 -mask 255.255.255.0
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/a -network 192.168.0/24
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/a -network 3ffe:1ce1:1:fe80::/64
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/u2 -maproot=root friends
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/u2 -alldirs -network cis-net -mask cis-mask
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/cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0
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.Ed
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.Pp
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Given that
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.Pa /usr , /u , /a
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and
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.Pa /u2
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are
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local file system mount points, the above example specifies the following:
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.Pp
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The file system rooted at
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.Pa /usr
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is exported to hosts
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.Em friends
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where friends is specified in the netgroup file
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with users mapped to their remote credentials and
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root mapped to UID 0 and group 10.
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It is exported read-write and the hosts in
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.Dq friends
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can mount either
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.Pa /usr
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or
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.Pa /usr/local .
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It is exported to
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.Em 131.104.48.16
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and
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.Em grumpy.cis.uoguelph.ca
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with users mapped to their remote credentials and
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root mapped to the user and groups associated with
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.Dq daemon ;
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it is exported to the rest of the world as read-only with
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all users mapped to the user and groups associated with
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.Dq nobody .
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.Pp
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The file system rooted at
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.Pa /u
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is exported to all hosts on the subnetwork
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.Em 131.104.48
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with root mapped to the UID for
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.Dq bin
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and with no group access.
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.Pp
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The file system rooted at
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.Pa /u2
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is exported to the hosts in
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.Dq friends
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with root mapped to UID and groups
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associated with
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.Dq root ;
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it is exported to all hosts on network
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.Dq cis-net
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allowing mounts at any
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directory within /u2.
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.Pp
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The file system rooted at
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.Pa /a
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is exported to the network 192.168.0.0, with a netmask of 255.255.255.0.
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However, the netmask length in the entry for
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.Pa /a
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is not specified through a
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.Fl mask
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option, but through the
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.Li / Ns Ar prefix
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notation.
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.Pp
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The file system rooted at
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.Pa /a
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is also exported to the IPv6 network
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.Li 3ffe:1ce1:1:fe80::
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address, using the upper 64 bits as the prefix.
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Note that, unlike with IPv4 network addresses, the specified network
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address must be complete, and not just contain the upper bits.
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With IPv6 addresses, the
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.Fl mask
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option must not be used.
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.Pp
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The file system rooted at
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.Pa /cdrom
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will be exported read-only to the entire network 192.168.33.0/24, including
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all its subdirectories.
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Since
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.Pa /cdrom
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is the conventional mountpoint for a CD-ROM device, this export will
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fail if no CD-ROM medium is currently mounted there since that line
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would then attempt to export a subdirectory of the root file system
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with the
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.Fl alldirs
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option which is not allowed.
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The
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.Fl quiet
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option will then suppress the error message for this condition that
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would normally be syslogged.
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As soon as an actual CD-ROM is going to be mounted,
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.Xr mount 8
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will notify
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.Xr mountd 8
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about this situation, and the
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.Pa /cdrom
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file system will be exported as intended.
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Note that without using the
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.Fl alldirs
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option, the export would always succeed.
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While there is no CD-ROM medium mounted under
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.Pa /cdrom ,
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it would export the (normally empty) directory
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.Pa /cdrom
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of the root file system instead.
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.Sh SEE ALSO
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.Xr netgroup 5 ,
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.Xr mountd 8 ,
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.Xr nfsd 8 ,
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.Xr showmount 8
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.Sh BUGS
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The export options are tied to the local mount points in the kernel and
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must be non-contradictory for any exported subdirectory of the local
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server mount point.
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It is recommended that all exported directories within the same server
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file system be specified on adjacent lines going down the tree.
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You cannot specify a hostname that is also the name of a netgroup.
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Specifying the full domain specification for a hostname can normally
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circumvent the problem.
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