18a3dd1e34
that it really wasn't intended as a security feature. Wording mostly by: simon Discussed with: secteam
492 lines
14 KiB
Groff
492 lines
14 KiB
Groff
.\" Copyright (c) 1980, 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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.\" @(#)mount.8 8.8 (Berkeley) 6/16/94
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.\" $FreeBSD$
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.\"
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.Dd November 26, 2004
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.Dt MOUNT 8
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.Os
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.Sh NAME
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.Nm mount
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.Nd mount file systems
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.Sh SYNOPSIS
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.Nm
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.Op Fl adfpruvw
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.Op Fl F Ar fstab
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.Op Fl o Ar options
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.Op Fl t Ar ufs | external_type
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.Nm
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.Op Fl dfpruvw
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.Ar special | node
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.Nm
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.Op Fl dfpruvw
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.Op Fl o Ar options
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.Op Fl t Ar ufs | external_type
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.Ar special 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
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.Ar "special device"
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or the remote node (rhost:path) on to the file system tree at the point
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.Ar node .
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If either
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.Ar special
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or
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.Ar node
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are not provided, the appropriate information is taken from the
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.Xr fstab 5
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file.
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.Pp
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The system maintains a list of currently mounted file systems.
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If no arguments are given to
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.Nm ,
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this list is printed.
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.Pp
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The options are as follows:
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.Bl -tag -width indent
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.It Fl a
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All the file systems described in
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.Xr fstab 5
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are mounted.
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Exceptions are those marked as
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.Dq noauto ,
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excluded by the
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.Fl t
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flag (see below), or if they are already mounted (except the
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root file system which is always remounted to preserve
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traditional single user mode behavior).
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.It Fl d
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Causes everything to be done except for the actual system call.
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This option is useful in conjunction with the
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.Fl v
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flag to
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determine what the
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.Nm
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command is trying to do.
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.It Fl F Ar fstab
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Specify the
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.Pa fstab
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file to use.
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.It Fl f
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Forces the revocation of write access when trying to downgrade
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a file system mount status from read-write to read-only.
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Also
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forces the R/W mount of an unclean file system (dangerous; use with
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caution).
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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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In case of conflicting options being specified, the rightmost option
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takes effect.
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The following options are available:
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.Bl -tag -width indent
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.It Cm acls
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Enable Access Control Lists, or ACLS, which can be customized via the
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.Xr setfacl 1
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and
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.Xr getfacl 1
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commands.
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.It Cm async
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All
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.Tn I/O
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to the file system should be done asynchronously.
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This is a
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.Em dangerous
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flag to set,
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and should not be used unless you are prepared to recreate the file
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system should your system crash.
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.It Cm current
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When used with the
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.Fl u
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flag, this is the same as specifying the options currently in effect for
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the mounted file system.
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.It Cm force
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The same as
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.Fl f ;
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forces the revocation of write access when trying to downgrade
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a file system mount status from read-write to read-only.
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Also
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forces the R/W mount of an unclean file system (dangerous; use with caution).
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.It Cm fstab
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When used with the
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.Fl u
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flag, this is the same as specifying all the options listed in the
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.Xr fstab 5
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file for the file system.
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.It Cm multilabel
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Enable multi-label Mandatory Access Control, or MAC, on the specified file
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system.
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If the file system supports multilabel operation, individual labels will
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be maintained for each object in the file system, rather than using a
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single label for all objects.
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An alternative to the
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.Fl l
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flag in
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.Xr tunefs 8 .
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See
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.Xr mac 4
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for more information, which cause the multilabel mount flag to be set
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automatically at mount-time.
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.It Cm noasync
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Metadata I/O should be done synchronously, while data I/O should be done
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asynchronously.
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This is the default.
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.It Cm noatime
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Do not update the file access time when reading from a file.
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This option
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is useful on file systems where there are large numbers of files and
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performance is more critical than updating the file access time (which is
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rarely ever important).
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This option is currently only supported on local file systems.
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.It Cm noauto
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This file system should be skipped when
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.Nm
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is run with the
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.Fl a
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flag.
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.It Cm noclusterr
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Disable read clustering.
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.It Cm noclusterw
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Disable write clustering.
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.It Cm noexec
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Do not allow execution of any binaries on the mounted file system.
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This option is useful for a server that has file systems containing
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binaries for architectures other than its own.
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Note: This option was not designed as a security feature and no
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guarantee is made that it will prevent malicious code execution; for
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example, it is still possible to execute scripts which reside on a
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.Cm noexec
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mounted partition.
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.It Cm nosuid
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Do not allow set-user-identifier or set-group-identifier bits to take effect.
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Note: this option is worthless if a public available suid or sgid
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wrapper like
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.Xr suidperl 1
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is installed on your system.
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It is set automatically when the user does not have super-user privileges.
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.It Cm nosymfollow
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Do not follow symlinks
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on the mounted file system.
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.It Cm ro
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The same as
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.Fl r ;
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mount the file system read-only (even the super-user may not write it).
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.It Cm sync
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All
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.Tn I/O
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to the file system should be done synchronously.
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.It Cm snapshot
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This option allows a snapshot of the specified file system to be taken.
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The
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.Fl u
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flag is required with this option.
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Note that snapshot files must be created in the file system that is being
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snapshotted.
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You may create up to 20 snapshots per file system.
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Active snapshots are recorded in the superblock, so they persist across unmount
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and remount operations and across system reboots.
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When you are done with a snapshot, it can be removed with the
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.Xr rm 1
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command.
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Snapshots may be removed in any order, however you may not get back all the
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space contained in the snapshot as another snapshot may claim some of the blocks
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that it is releasing.
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Note that the schg flag is set on snapshots to ensure that not even the root
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user can write to them.
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The unlink command makes an exception for snapshot files in that it allows them
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to be removed even though they have the schg flag set, so it is not necessary to
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clear the schg flag before removing a snapshot file.
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.Pp
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Once you have taken a snapshot, there are three interesting things that you can
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do with it:
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.Pp
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.Bl -enum -compact
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.It
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Run
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.Xr fsck 8
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on the snapshot file.
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Assuming that the file system was clean when it was mounted, you should always
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get a clean (and unchanging) result from running fsck on the snapshot.
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This is essentially what the background fsck process does.
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.Pp
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.It
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Run
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.Xr dump 8
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on the snapshot.
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You will get a dump that is consistent with the file system as of the timestamp
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of the snapshot.
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.Pp
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.It
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Mount the snapshot as a frozen image of the file system.
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To mount the snapshot
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.Pa /var/snapshot/snap1 :
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.Bd -literal
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mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4
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mount -r /dev/md4 /mnt
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.Ed
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.Pp
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|
You can now cruise around your frozen
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.Pa /var
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file system at
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.Pa /mnt .
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Everything will be in the same state that it was at the time the snapshot was
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taken.
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The one exception is that any earlier snapshots will appear as zero length
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files.
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When you are done with the mounted snapshot:
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.Bd -literal
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umount /mnt
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mdconfig -d -u 4
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.Ed
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.Pp
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Further details can be found in the file at
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.Pa /usr/src/sys/ufs/ffs/README.snapshot .
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.El
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.It Cm suiddir
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A directory on the mounted file system will respond to the SUID bit
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being set, by setting the owner of any new files to be the same
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as the owner of the directory.
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New directories will inherit the bit from their parents.
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Execute bits are removed from
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the file, and it will not be given to root.
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.Pp
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This feature is designed for use on fileservers serving PC users via
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ftp, SAMBA, or netatalk.
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It provides security holes for shell users and as
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such should not be used on shell machines, especially on home directories.
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This option requires the SUIDDIR
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option in the kernel to work.
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Only UFS file systems support this option.
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See
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.Xr chmod 2
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for more information.
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.It Cm update
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The same as
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.Fl u ;
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indicate that the status of an already mounted file system should be changed.
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.It Cm union
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Causes the namespace at the mount point to appear as the union
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of the mounted file system root and the existing directory.
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Lookups will be done in the mounted file system first.
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If those operations fail due to a non-existent file the underlying
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directory is then accessed.
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All creates are done in the mounted file system.
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.El
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.Pp
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Any additional options specific to a file system type that is not
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one of the internally known types (see the
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.Fl t
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option) may be passed as a comma separated list; these options are
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distinguished by a leading
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.Dq \&-
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(dash).
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Options that take a value are specified using the syntax -option=value.
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For example, the
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.Nm
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command:
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.Bd -literal -offset indent
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mount -t unionfs -o -b /sys $HOME/sys
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.Ed
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.Pp
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causes
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.Nm
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to execute the equivalent of:
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.Bd -literal -offset indent
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/sbin/mount_unionfs -b /sys $HOME/sys
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.Ed
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.Pp
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Additional options specific to file system types
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which are not internally known
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(see the description of the
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.Fl t
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option below)
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may be described in the manual pages for the associated
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.Pa /sbin/mount_ Ns Sy XXX
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utilities.
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.It Fl p
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Print mount information in
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.Xr fstab 5
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format.
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Implies also the
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.Fl v
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option.
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.It Fl r
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The file system is to be mounted read-only.
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Mount the file system read-only (even the super-user may not write it).
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The same as the
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.Cm ro
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argument to the
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.Fl o
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option.
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.It Fl t Ar ufs | external_type
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The argument following the
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.Fl t
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is used to indicate the file system type.
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The type
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.Ar ufs
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is the default.
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The
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.Fl t
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option can be used
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to indicate that the actions should only be taken on
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file systems of the specified type.
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More than one type may be specified in a comma separated list.
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The list of file system types can be prefixed with
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.Dq no
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to specify the file system types for which action should
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.Em not
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be taken.
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For example, the
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.Nm
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command:
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.Bd -literal -offset indent
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mount -a -t nonfs,nullfs
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.Ed
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.Pp
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mounts all file systems except those of type
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.Tn NFS
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and
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.Tn NULLFS .
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.Pp
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If the type is not one of the internally known types,
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.Nm
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will attempt to execute a program in
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.Pa /sbin/mount_ Ns Sy XXX
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where
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.Sy XXX
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is replaced by the type name.
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For example, nfs file systems are mounted by the program
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.Pa /sbin/mount_nfs .
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.Pp
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Most file systems will be dynamically loaded by the kernel
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if not already present, and if the kernel module is available.
|
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.It Fl u
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The
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.Fl u
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flag indicates that the status of an already mounted file
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system should be changed.
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Any of the options discussed above (the
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.Fl o
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option)
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may be changed;
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also a file system can be changed from read-only to read-write
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or vice versa.
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An attempt to change from read-write to read-only will fail if any
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files on the file system are currently open for writing unless the
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.Fl f
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flag is also specified.
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The set of options is determined by applying the options specified
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in the argument to
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.Fl o
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and finally applying the
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.Fl r
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or
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.Fl w
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option.
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.It Fl v
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Verbose mode.
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.It Fl w
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The file system object is to be read and write.
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.El
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.Sh ENVIRONMENT
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.Bl -tag -width ".Ev PATH_FSTAB"
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.It Ev PATH_FSTAB
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If the environment variable
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.Ev PATH_FSTAB
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is set, all operations are performed against the specified file.
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.Ev PATH_FSTAB
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will not be honored if the process environment or memory address space is
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considered
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.Dq tainted .
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|
(See
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.Xr issetugid 2
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for more information.)
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.El
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.Sh FILES
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.Bl -tag -width /etc/fstab -compact
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.It Pa /etc/fstab
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file system table
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.El
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|
.Sh DIAGNOSTICS
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Various, most of them are self-explanatory.
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.Pp
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.Dl XXXXX file system is not available
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|
.Pp
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|
The kernel does not support the respective file system type.
|
|
Note that
|
|
support for a particular file system might be provided either on a static
|
|
(kernel compile-time), or dynamic basis (loaded as a kernel module by
|
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.Xr kldload 8 ) .
|
|
.Sh SEE ALSO
|
|
.Xr getfacl 1 ,
|
|
.Xr setfacl 1 ,
|
|
.Xr mount 2 ,
|
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.Xr acl 3 ,
|
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.Xr mac 4 ,
|
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.Xr fstab 5 ,
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.Xr kldload 8 ,
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.Xr mount_cd9660 8 ,
|
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.Xr mount_devfs 8 ,
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|
.Xr mount_ext2fs 8 ,
|
|
.Xr mount_fdescfs 8 ,
|
|
.Xr mount_hpfs 8 ,
|
|
.Xr mount_linprocfs 8 ,
|
|
.Xr mount_msdosfs 8 ,
|
|
.Xr mount_nfs 8 ,
|
|
.Xr mount_ntfs 8 ,
|
|
.Xr mount_nullfs 8 ,
|
|
.Xr mount_nwfs 8 ,
|
|
.Xr mount_portalfs 8 ,
|
|
.Xr mount_procfs 8 ,
|
|
.Xr mount_smbfs 8 ,
|
|
.Xr mount_std 8 ,
|
|
.Xr mount_udf 8 ,
|
|
.Xr mount_umapfs 8 ,
|
|
.Xr mount_unionfs 8 ,
|
|
.Xr umount 8
|
|
.Sh CAVEATS
|
|
After a successful
|
|
.Nm ,
|
|
the permissions on the original mount point determine if
|
|
.Pa ..\&
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|
is accessible from the mounted file system.
|
|
The minimum permissions for
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|
the mount point for traversal across the mount point in both
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|
directions to be possible for all users is 0111 (execute for all).
|
|
.Sh HISTORY
|
|
A
|
|
.Nm
|
|
utility appeared in
|
|
.At v1 .
|
|
.Sh BUGS
|
|
It is possible for a corrupted file system to cause a crash.
|