f0e5ce5f10
The two options are * nocover/cover: Prevent/allow mounting over an existing root mountpoint. E.g., "mount -t ufs -o nocover /dev/sd1a /usr/local" will fail if /usr/local is already a mountpoint. * emptydir/noemptydir: Prevent/allow mounting on a non-empty directory. E.g., "mount -t ufs -o emptydir /dev/sd1a /usr" will fail. Neither of these options is intended to be a default, for historical and compatibility reasons. Reviewed by: allanjude, kib Differential Revision: https://reviews.freebsd.org/D21458
604 lines
16 KiB
Groff
604 lines
16 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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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
|
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)mount.8 8.8 (Berkeley) 6/16/94
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.\" $FreeBSD$
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.\"
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.Dd August 28, 2019
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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 adflpruvw
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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 Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar 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 Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar 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 nmount 2
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system call to prepare and graft a
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.Ar special
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device 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 Li noauto ,
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those marked as
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.Dq Li late
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(unless the
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.Fl l
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option was specified),
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those 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 L
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When used in conjunction with the
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.Fl a
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option, mount
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.Em only
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those file systems which are marked as
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.Dq Li late .
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.It Fl l
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When used in conjunction with the
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.Fl a
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option, also mount those file systems which are marked as
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.Dq Li late .
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.It Fl n
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For compatibility with some other implementations, this flag is
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currently a no-op.
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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 POSIX.1e 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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This flag is mutually exclusive with
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.Cm nfsv4acls
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flag.
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.It Cm async
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All I/O 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, since it does not guarantee that the file system structure
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on the disk will remain consistent.
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For this reason, the
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.Cm async
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flag should be used sparingly, and only when some data recovery
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mechanism is present.
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.It Cm automounted
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This flag indicates that the file system was mounted by
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.Xr automountd 8 .
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Automounted file systems are automatically unmounted by
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.Xr autounmountd 8 .
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.It Cm autoro
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Mount the file system read-write.
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If that fails with an error that suggests that the media could be read-only,
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then automatically try to mount the file system read-only.
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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 emptydir
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Require that the mount point directory be empty.
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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 late
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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 but without the
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.Fl l
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flag.
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.It Cm mountprog Ns = Ns Aq Ar program
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Force
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.Nm
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to use the specified program to mount the file system, instead of calling
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.Xr nmount 2
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directly.
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For example:
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.Bd -literal
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mount -t foofs -o mountprog=/mydir/fooprog /dev/cd0 /mnt
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.Ed
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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 nfsv4acls
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|
Enable NFSv4 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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This flag is mutually exclusive with
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.Cm acls
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flag.
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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 nocover
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Do not mount if the requested mount point is already
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the root of a mount point.
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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 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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.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 sync
|
|
All I/O to the file system should be done synchronously.
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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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.It Cm untrusted
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|
The file system is untrusted and the kernel should use more
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extensive checks on the file-system's metadata before using it.
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This option is intended to be used when mounting file systems
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from untrusted media such as USB memory sticks or other
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externally-provided media.
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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).
|
|
For example, the
|
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.Nm
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|
command:
|
|
.Bd -literal -offset indent
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|
mount -t cd9660 -o -e /dev/cd0 /cdrom
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|
.Ed
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.Pp
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|
causes
|
|
.Nm
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|
to execute the equivalent of:
|
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.Bd -literal -offset indent
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/sbin/mount_cd9660 -e /dev/cd0 /cdrom
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.Ed
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.Pp
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|
Options that take a value are specified using the -option=value syntax:
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|
.Bd -literal -offset indent
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mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt
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.Ed
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.Pp
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|
is equivalent to
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.Bd -literal -offset indent
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/sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt
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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
|
|
.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.
|
|
Mount the file system read-only (even the super-user may not write it).
|
|
The same as the
|
|
.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 Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar 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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|
.Cm ufs
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|
is the default.
|
|
The
|
|
.Fl t
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|
option can be used
|
|
to indicate that the actions should only be taken on
|
|
file systems of the specified type.
|
|
More than one type may be specified in a comma separated list.
|
|
The list of file system types can be prefixed with
|
|
.Cm no
|
|
to specify the file system types for which action should
|
|
.Em not
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|
be taken.
|
|
For example, the
|
|
.Nm
|
|
command:
|
|
.Bd -literal -offset indent
|
|
mount -a -t nonfs,nullfs
|
|
.Ed
|
|
.Pp
|
|
mounts all file systems except those of type NFS and NULLFS.
|
|
.Pp
|
|
The default behavior of
|
|
.Nm
|
|
is to pass the
|
|
.Fl t
|
|
option directly to the
|
|
.Xr nmount 2
|
|
system call in the
|
|
.Li fstype
|
|
option.
|
|
.Pp
|
|
However, for the following file system types:
|
|
.Cm cd9660 ,
|
|
.Cm mfs ,
|
|
.Cm msdosfs ,
|
|
.Cm nfs ,
|
|
.Cm nullfs ,
|
|
.Cm smbfs ,
|
|
.Cm udf ,
|
|
and
|
|
.Cm unionfs
|
|
.Nm
|
|
will not call
|
|
.Xr nmount 2
|
|
directly and will instead attempt to execute a program in
|
|
.Pa /sbin/mount_ Ns Ar type
|
|
where
|
|
.Ar type
|
|
is replaced by the file system type name.
|
|
For example,
|
|
.Cm nfs
|
|
file systems are mounted by the program
|
|
.Pa /sbin/mount_nfs .
|
|
.Pp
|
|
Most file systems will be dynamically loaded by the kernel
|
|
if not already present, and if the kernel module is available.
|
|
.It Fl u
|
|
The
|
|
.Fl u
|
|
flag indicates that the status of an already mounted file
|
|
system should be changed.
|
|
Any of the options discussed above (the
|
|
.Fl o
|
|
option)
|
|
may be changed;
|
|
also a file system can be changed from read-only to read-write
|
|
or vice versa.
|
|
An attempt to change from read-write to read-only will fail if any
|
|
files on the file system are currently open for writing unless the
|
|
.Fl f
|
|
flag is also specified.
|
|
The set of options is determined by applying the options specified
|
|
in the argument to
|
|
.Fl o
|
|
and finally applying the
|
|
.Fl r
|
|
or
|
|
.Fl w
|
|
option.
|
|
.It Fl v
|
|
Verbose mode.
|
|
If the
|
|
.Fl v
|
|
is used alone, show all file systems, including those that were mounted with the
|
|
.Dv MNT_IGNORE
|
|
flag and show additional information about each file system (including fsid
|
|
when run by root).
|
|
.It Fl w
|
|
The file system object is to be read and write.
|
|
.El
|
|
.Sh ENVIRONMENT
|
|
.Bl -tag -width ".Ev PATH_FSTAB"
|
|
.It Ev PATH_FSTAB
|
|
If the environment variable
|
|
.Ev PATH_FSTAB
|
|
is set, all operations are performed against the specified file.
|
|
.Ev PATH_FSTAB
|
|
will not be honored if the process environment or memory address space is
|
|
considered
|
|
.Dq tainted .
|
|
(See
|
|
.Xr issetugid 2
|
|
for more information.)
|
|
.El
|
|
.Sh FILES
|
|
.Bl -tag -width /etc/fstab -compact
|
|
.It Pa /etc/fstab
|
|
file system table
|
|
.El
|
|
.Sh DIAGNOSTICS
|
|
Various, most of them are self-explanatory.
|
|
.Pp
|
|
.Dl XXXXX file system is not available
|
|
.Pp
|
|
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
|
|
.Xr kldload 8 ) .
|
|
.Sh SEE ALSO
|
|
.Xr getfacl 1 ,
|
|
.Xr setfacl 1 ,
|
|
.Xr nmount 2 ,
|
|
.Xr acl 3 ,
|
|
.Xr mac 4 ,
|
|
.Xr cd9660 5 ,
|
|
.Xr devfs 5 ,
|
|
.Xr ext2fs 5 ,
|
|
.Xr fstab 5 ,
|
|
.Xr procfs 5 ,
|
|
.Xr tmpfs 5 ,
|
|
.Xr automount 8 ,
|
|
.Xr fstyp 8 ,
|
|
.Xr kldload 8 ,
|
|
.Xr mount_cd9660 8 ,
|
|
.Xr mount_msdosfs 8 ,
|
|
.Xr mount_nfs 8 ,
|
|
.Xr mount_nullfs 8 ,
|
|
.Xr mount_smbfs 8 ,
|
|
.Xr mount_udf 8 ,
|
|
.Xr mount_unionfs 8 ,
|
|
.Xr umount 8 ,
|
|
.Xr zfs 8 ,
|
|
.Xr zpool 8
|
|
.Sh HISTORY
|
|
A
|
|
.Nm
|
|
utility appeared in
|
|
.At v1 .
|
|
.Sh CAVEATS
|
|
After a successful
|
|
.Nm ,
|
|
the permissions on the original mount point determine if
|
|
.Pa ..\&
|
|
is accessible from the mounted file system.
|
|
The minimum permissions for
|
|
the mount point for traversal across the mount point in both
|
|
directions to be possible for all users is 0111 (execute for all).
|
|
.Pp
|
|
Use of the
|
|
.Nm
|
|
is preferred over the use of the file system specific
|
|
.Pa mount_ Ns Sy XXX
|
|
commands.
|
|
In particular,
|
|
.Xr mountd 8
|
|
gets a
|
|
.Dv SIGHUP
|
|
signal (that causes an update of the export list)
|
|
only when the file system is mounted via
|
|
.Nm .
|
|
.Sh BUGS
|
|
It is possible for a corrupted file system to cause a crash.
|