NetBSD/sbin/mount/mount.8

.\"	$NetBSD: mount.8,v 1.52 2006/02/12 01:32:06 chs Exp $
.\"
.\" Copyright (c) 1980, 1989, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)mount.8	8.8 (Berkeley) 6/16/94
.\"
.Dd February 11, 2006
.Dt MOUNT 8
.Os
.Sh NAME
.Nm mount
.Nd mount file systems
.Sh SYNOPSIS
.Nm
.Op Fl Aadfruvw
.Op Fl t Ar type
.Nm
.Op Fl dfruvw
.Ar special | node
.Nm
.Op Fl dfruvw
.Op Fl o Ar options
.Op Fl t Ar type
.Ar special node
.Sh DESCRIPTION
The
.Nm
command invokes a file system-specific program to prepare and graft the
.Ar special
device or remote node (rhost:path) on to the file system tree at the point
.Ar node .
.Pp
If either
.Ar special
or
.Ar node
are not provided, the appropriate information is taken from the
.Xr fstab 5
file.
The provided argument is looked up first in the
.Dq fs_file ,
then in the
.Dq fs_spec
column.
If the matching entry in
.Xr fstab 5
has the string
.Dq Li from_mount
as its
.Dq fs_spec
field, the device or remote file system already mounted at
the location specified by
.Dq fs_spec
will be used.
.Pp
If both
.Ar special
and
.Ar node
are given, the disklabel is checked for the file system type.
.Pp
In
.Nx ,
a file system can only be mounted by an ordinary user who owns the
point
.Ar node
and has access to the
.Ar special
device (at least read permissions).
In addition, the
.Em vfs.generic.usermount
.Xr sysctl 3
must be set to 1 to permit file system mounting by ordinary users.
See also
.Xr sysctl 8 .
.Pp
The system maintains a list of currently mounted file systems.
If no arguments are given to
.Nm ,
this list is printed.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl A
Causes
.Nm
to try to mount all of the file systems listed in the
.Xr fstab 5
file except those for which the
.Dq noauto
option is specified.
.It Fl a
Similar to the
.Fl A
flag, except that if a file system (other than the root file system)
appears to be already mounted,
.Nm
will not try to mount it again.
.Nm
assumes that a file system is already mounted if a file system with
the same type is mounted on the given mount point.
More stringent checks are not possible because some file system types
report strange values for the mounted-from device for mounted file
systems.
.It Fl d
Causes everything to be done except for the invocation of
the file system-specific program.
This option is useful in conjunction with the
.Fl v
flag to determine what the
.Nm
command is trying to do.
.It Fl f
Forces the revocation of write access when trying to downgrade
a file system mount status from read-write to read-only.
.It Fl o
Options are specified with a
.Fl o
flag followed by a comma separated string of options.
The following options are available:
.Bl -tag -width nocoredump
.It Cm async
All
.Tn I/O
to the file system should be done asynchronously.
In the event of a crash,
.Em "it is impossible for the system to verify the integrity of data on a file system mounted with this option" .
You should only use this option if you have an application-specific data
recovery mechanism, or are willing to recreate the file system from scratch.
.It Cm noasync
Clear
.Cm async
mode.
.It Cm force
The same as
.Fl f ;
forces the revocation of write access when trying to downgrade
a file system mount status from read-write to read-only.
.It Cm getargs
Retrieves the file system specific mount arguments for the given
mounted file system and prints them.
.It Cm hidden
By setting the
.Dv MNT_IGNORE
flag,
causes the mount point to be excluded from the
list of file systems shown by default with
.Xr df 1 .
.It Cm noatime
Never update the access time field for files.
This option is useful for optimizing read performance on file systems
that are used as news spools.
.It Cm noauto
This file system should be skipped when mount is run with the
.Fl a
flag.
.It Cm nocoredump
Do not allow programs to create crash dumps (core files) on the file system.
This option can be used to help protect sensitive
data by keeping core files (which may contain sensitive data)
from being created on insecure file systems.
Only core files that would be created by program crashes are
prevented by use of this flag; the behavior of
.Xr savecore 8
is not affected.
.It Cm nodev
Do not interpret character or block special devices on the file system.
This option is useful for a server that has file systems containing
special devices for architectures other than its own.
.It Cm nodevmtime
Do not update modification times on device special files.
This option is useful on laptops
or other systems that perform power management.
.It Cm noexec
Do not allow execution of any binaries on the mounted file system.
This option is useful for a server that has file systems containing
binaries for architectures other than its own.
.It Cm nosuid
Do not allow set-user-identifier or set-group-identifier bits to take effect.
.It Cm port
(NFS only) Use the specified NFS port.
.It Cm rdonly
The same as
.Fl r ;
mount the file system read-only (even the super-user may not write it).
.It Cm reload
Reload all incore data for a file system.
This is used mainly after running
.Xr fsck 8
on the root file system and finding things to fix.
The file system must be mounted read-only.
All cached meta-data are invalidated, superblock and summary information
is re-read from disk, all cached inactive vnodes and file data are
invalidated and all inode data are re-read for all active vnodes.
.It Cm softdep
(FFS only) Mount the file system using soft dependencies.
This means that metadata will not be written immediately,
but is written in an ordered fashion to keep the
on-disk state of the file system consistent.
This results in significant speedups for file create/delete operations.
This option will be ignored when using the
.Fl u
flag and a file system is already mounted read/write.
This option has gone through moderate to heavy testing,
but should still be used with care.
A file system mounted with
.Cm softdep
can not be mounted with
.Cm async .
It requires the
.Dv SOFTDEP
option to be enabled in the running kernel.
.It Cm symperm
Recognize permission of symbolic link when reading or traversing link.
.It Cm sync
All
.Tn I/O
to the file system should be done synchronously.
This is not equivalent to the normal mode in which only
metadata is written synchronously.
.It Cm nosync
Clear
.Cm sync
mode.
.It Cm union
Causes the namespace at the mount point to appear as the union
of the mounted file system root and the existing directory.
Lookups will be done in the mounted file system first.
If those operations fail due to a non-existent file the underlying
directory is then accessed.
All creates are done in the mounted file system, except for the fdesc
file system.
.It Cm update
The same as
.Fl u ;
indicate that the status of an already mounted file system should be changed.
.El
.Pp
Any additional options specific to a given file system type (see the
.Fl t
option) may be passed as a comma separated list; these options are
distinguished by a leading
.Dq \&-
(dash).
Options that take a value are specified using the syntax -option=value.
For example, the mount command:
.Bd -literal -offset indent
mount -t mfs -o nosuid,-N,-s=32m swap /tmp
.Ed
.Pp
causes
.Nm
to execute the equivalent of:
.Bd -literal -offset indent
/sbin/mount_mfs -o nosuid -N -s 32m swap /tmp
.Ed
.It Fl r
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
.Dq rdonly
argument to the
.Fl o
option.
.It Fl t Ar type
The argument following the
.Fl t
is used to indicate the file system type.
The type
.Ar ffs
is the default.
The
.Fl t
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
.Dq no
to specify the file system types for which action should
.Em not
be taken.
For example, the
.Nm
command:
.Bd -literal -offset indent
mount -a -t nonfs,mfs
.Ed
.Pp
mounts all file systems except those of type
.Tn NFS
and
.Tn MFS .
.Pp
.Nm
will attempt to execute a program in
.Pa /sbin/mount_ Ns Em XXX
where
.Em XXX
is replaced by the type name.
For example, nfs file systems are mounted by the program
.Pa /sbin/mount_nfs .
.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 first extracting the options
for the file system from the
.Xr fstab 5
file, then applying any options specified by the
.Fl o
argument,
and finally applying the
.Fl r
or
.Fl w
option.
.It Fl v
Verbose mode.
If this flag is specified more than once, then the
file system-specific mount arguments are printed for the given mounted
file system.
.It Fl w
The file system object is to be read and write.
.El
.Pp
The options specific to the various file system types are
described in the manual pages for those file systems'
.Nm mount_XXX
commands.
For instance the options specific to Berkeley
Fast File System (FFS) are described in the
.Xr mount_ffs 8
manual page.
.Pp
The particular type of file system in each partition of a disk can
be found by examining the disk label with the
.Xr disklabel 8
command.
.Sh FILES
.Bl -tag -width /etc/fstab -compact
.It Pa /etc/fstab
file system table
.El
.Sh EXAMPLES
Some useful examples:
.Pp
.Bl -hang -offset indent -width "MS-DOS"
.It Tn CD-ROM
.br
mount -t cd9660 -r /dev/cd0a /cdrom
.It Tn MS-DOS
.br
mount -t msdos /dev/fd0a /floppy
.It Tn NFS
.br
mount nfs-server-host:/directory/path /mount-point
.It Tn MFS (32 megabyte)
.br
mount -t mfs -o nosuid,-s=32m swap /tmp
.El
.Pp
The
.Dq noauto
directive in
.Pa /etc/fstab
can be used to make it easy to manually mount and unmount removable
media using just the mountpoint filename, with an entry like this:
.Pp
.Dl /dev/cd0a  /cdrom  cd9660 ro,noauto 0 0
.Pp
That would allow a simple command like
.Qq mount /cdrom
or
.Qq umount /cdrom
for media using the
.Tn ISO-9660
file system format in the first
.Tn CD-ROM
drive.
.Sh SEE ALSO
.Xr df 1 ,
.Xr mount 2 ,
.Xr fstab 5 ,
.Xr disklabel 8 ,
.Xr fsck 8 ,
.Xr mount_ados 8 ,
.Xr mount_cd9660 8 ,
.Xr mount_ext2fs 8 ,
.Xr mount_fdesc 8 ,
.Xr mount_ffs 8 ,
.Xr mount_filecore 8 ,
.Xr mount_kernfs 8 ,
.Xr mount_lfs 8 ,
.Xr mount_mfs 8 ,
.Xr mount_msdos 8 ,
.Xr mount_nfs 8 ,
.Xr mount_ntfs 8 ,
.Xr mount_null 8 ,
.Xr mount_overlay 8 ,
.Xr mount_portal 8 ,
.Xr mount_procfs 8 ,
.Xr mount_udf 8 ,
.Xr mount_umap 8 ,
.Xr mount_union 8 ,
.Xr umount 8
.Sh HISTORY
A
.Nm
command appeared in
.At v6 .