mount/mount.8

.\" Copyright (c) 1996 Andries Brouwer
.\"
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.\" (c) 1980, 1989, 1991 The Regents of the University of California
.\" and had been heavily modified by Rik Faith and myself.
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.\" Fragments of text were written by Werner Almesberger, Remy Card,
.\" Stephen Tweedie and Eric Youngdale.
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.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
.\" USA.
.\"
.\" 960705, aeb: version for mount-2.7g
.\" 970114, aeb: xiafs and ext are dead; romfs is new
.\" 970623, aeb: -F option
.\" 970914, reg: -s option
.\" 981111, K.Garloff: /etc/filesystems
.\" 990111, aeb: documented /sbin/mount.smbfs
.\" 990730, Yann Droneaud <lch@multimania.com>: updated page
.\" 991214, Elrond <Elrond@Wunder-Nett.org>: added some docs on devpts
.\" 010714, Michael K. Johnson <johnsonm@redhat.com> added -O
.\" 010725, Nikita Danilov <NikitaDanilov@Yahoo.COM>: reiserfs options
.\" 011124, Karl Eichwalder <ke@gnu.franken.de>: tmpfs options
.\"
.TH MOUNT 8 "14 September 1997" "Linux 2.0" "Linux Programmer's Manual"
.SH NAME
mount \- mount a file system
.SH SYNOPSIS
.BI "mount [\-lhV]"
.LP
.BI "mount \-a [\-fFnrsvw] [\-t " vfstype "] [\-O " optlist ]
.br
.BI "mount [\-fnrsvw] [\-o " options " [,...]] " "device " | " dir"
.br
.BI "mount [\-fnrsvw] [\-t " vfstype "] [\-o " options "] " "device dir"
.SH DESCRIPTION
All files accessible in a Unix system are arranged in one big
tree, the file hierarchy, rooted at
.BR / .
These files can be spread out over several devices. The
.B mount
command serves to attach the file system found on some device
to the big file tree. Conversely, the
.BR umount (8)
command will detach it again.

The standard form of the
.B mount
command, is
.RS
.br
.BI "mount \-t" " type device dir"
.RE
This tells the kernel to attach the file system found on
.I device
(which is of type
.IR type )
at the directory
.IR dir .
The previous contents (if any) and owner and mode of
.I dir
become invisible, and as long as this file system remains mounted,
the pathname
.I dir
refers to the root of the file system on
.IR device .

Three forms of invocation do not actually mount anything:
.RS
.br
.B "mount \-h"
.RE
prints a help message;
.RS
.br
.B "mount \-V"
.RE
prints a version string; and just
.RS
.BI "mount [-l] [-t" " type" ]
.RE
lists all mounted file systems (of type
.IR type ).
The option \-l adds the (ext2, ext3 and XFS) labels in this listing.
See below.

.\" In fact since 2.3.99. At first the syntax was mount -t bind.
Since Linux 2.4.0 it is possible to remount part of the
file hierarchy somewhere else. The call is
.RS
.br
.B "mount --bind olddir newdir"
.RE
After this call the same contents is accessible in two places.

This call attaches only (part of) a single filesystem, not possible
submounts. The entire file hierarchy including submounts is attached
a second place using
.RS
.br
.B "mount --rbind olddir newdir"
.RE
.\" available since Linux 2.4.11.

Since Linux 2.5.1 it is possible to atomically move a subtree
to another place. The call is
.RS
.br
.B "mount --move olddir newdir"
.RE

The
.I proc
file system is not associated with a special device, and when
mounting it, an arbitrary keyword, such as
.I proc
can be used instead of a device specification.
(The customary choice
.I none
is less fortunate: the error message `none busy' from
.B umount
can be confusing.)

Most devices are indicated by a file name (of a block special device), like
.IR /dev/sda1 ,
but there are other possibilities. For example, in the case of an NFS mount,
.I device
may look like
.IR knuth.cwi.nl:/dir .
It is possible to indicate a block special device using its
volume label or UUID (see the \-L and \-U options below).

The file
.I /etc/fstab
(see
.BR fstab (5)),
may contain lines describing what devices are usually
mounted where, using which options. This file is used in three ways:
.LP
(i) The command
.RS
.br
.BI "mount \-a [\-t " type "] [\-O " optlist ]
.RE
(usually given in a bootscript) causes all file systems mentioned in
.I fstab
(of the proper type and/or having or not having the proper options)
to be mounted as indicated, except for those whose line contains the
.B noauto
keyword. Adding the
.B \-F
option will make mount fork, so that the
filesystems are mounted simultaneously.
.LP
(ii) When mounting a file system mentioned in
.IR fstab ,
it suffices to give only the device, or only the mount point.
.LP
(iii) Normally, only the superuser can mount file systems.
However, when
.I fstab
contains the
.B user
option on a line, then anybody can mount the corresponding system.
.LP
Thus, given a line
.RS
.br
.B "/dev/cdrom  /cd  iso9660  ro,user,noauto,unhide"
.RE
any user can mount the iso9660 file system found on his CDROM
using the command
.RS
.br
.B "mount /dev/cdrom"
.RE
or
.RS
.br
.B "mount /cd"
.RE
For more details, see
.BR fstab (5).
Only the user that mounted a filesystem can unmount it again.
If any user should be able to unmount, then use
.B users
instead of
.B user
in the
.I fstab
line.
The
.B owner
option is similar to the
.B user
option, with the restriction that the user must be the owner
of the special file. This may be useful e.g. for
.I /dev/fd
if a login script makes the console user owner of this device.

The programs
.B mount
and
.B umount
maintain a list of currently mounted file systems in the file
.IR /etc/mtab .
If no arguments are given to
.BR mount ,
this list is printed.
When the
.I proc
filesystem is mounted (say at
.IR /proc ),
the files
.I /etc/mtab
and
.I /proc/mounts
have very similar contents. The former has somewhat
more information, such as the mount options used,
but is not necessarily up-to-date (cf. the
.B \-n
option below). It is possible to replace
.I /etc/mtab
by a symbolic link to
.IR /proc/mounts ,
but some information is lost that way, and in particular
working with the loop device will be less convenient.

.SH OPTIONS
The full set of options used by an invocation of
.B mount
is determined by first extracting the
options for the file system from the
.I fstab
table, then applying any options specified by the
.B \-o
argument, and finally applying a
.BR \-r " or " \-w
option, when present.

Options available for the
.B mount
command:
.TP
.B \-V
Output version.
.TP
.B \-h
Print a help message.
.TP
.B \-v
Verbose mode.
.TP
.B \-a
Mount all filesystems (of the given types) mentioned in
.IR fstab .
.TP
.B \-F
(Used in conjunction with
.BR \-a .)
Fork off a new incarnation of mount for each device.
This will do the mounts on different devices or different NFS servers
in parallel.
This has the advantage that it is faster; also NFS timeouts go in
parallel. A disadvantage is that the mounts are done in undefined order.
Thus, you cannot use this option if you want to mount both
.I /usr
and
.IR /usr/spool .
.TP
.B \-f
Causes everything to be done except for the actual system call; if it's not
obvious, this ``fakes'' mounting the file system.  This option is useful in
conjunction with the
.B \-v
flag to determine what the
.B mount
command is trying to do. It can also be used to add entries for devices
that were mounted earlier with the -n option.
.TP
.B \-l
Add the ext2, ext3 and XFS labels in the mount output. Mount must have
permission to read the disk device (e.g. be suid root) for this to work.
One can set such a label for ext2 or ext3 using the
.BR e2label (8)
utility, or for XFS using
.BR xfs_admin (8).
.TP
.B \-n
Mount without writing in
.IR /etc/mtab .
This is necessary for example when
.I /etc
is on a read-only file system.
.TP
.B \-s
Tolerate sloppy mount options rather than failing. This will ignore
mount options not supported by a filesystem type. Not all filesystems
support this option. This option exists for support of the Linux
autofs\-based automounter.
.TP
.B \-r
Mount the file system read-only. A synonym is
.BR "\-o ro" .
.TP
.B \-w
Mount the file system read/write. This is the default. A synonym is
.BR "\-o rw" .
.TP
.BI \-L " label"
Mount the partition that has the specified
.IR label .
.TP
.BI \-U " uuid"
Mount the partition that has the specified
.IR uuid .
These two options require the file
.I /proc/partitions
(present since Linux 2.1.116) to exist.
.TP
.BI \-t " vfstype"
The argument following the
.B \-t
is used to indicate the file system type.  The file system types which are
currently supported are:
.IR adfs ,
.IR affs ,
.IR autofs ,
.IR coda ,
.IR coherent ,
.IR cramfs ,
.IR devpts ,
.IR efs ,
.IR ext ,
.IR ext2 ,
.IR ext3 ,
.IR hfs ,
.IR hpfs ,
.IR iso9660 ,
.IR jfs ,
.IR minix ,
.IR msdos ,
.IR ncpfs ,
.IR nfs ,
.IR ntfs ,
.IR proc ,
.IR qnx4 ,
.IR ramfs ,
.IR reiserfs ,
.IR romfs ,
.IR smbfs ,
.IR sysv ,
.IR tmpfs ,
.IR udf ,
.IR ufs ,
.IR umsdos ,
.IR vfat ,
.IR xenix ,
.IR xfs ,
.IR xiafs .
Note that coherent, sysv and xenix are equivalent and that
.I xenix
and
.I coherent
will be removed at some point in the future \(em use
.I sysv
instead. Since kernel version 2.1.21 the types
.I ext
and
.I xiafs
do not exist anymore.

For most types all the
.B mount
program has to do is issue a simple
.IR mount (2)
system call, and no detailed knowledge of the filesystem type is required.
For a few types however (like nfs, smbfs, ncpfs) ad hoc code is
necessary. The nfs ad hoc code is built in, but smbfs and ncpfs
have a separate mount program. In order to make it possible to
treat all types in a uniform way, mount will execute the program
.I /sbin/mount.TYPE
(if that exists) when called with type
.IR TYPE .
Since various versions of the
.I smbmount
program have different calling conventions,
.I /sbin/mount.smb
may have to be a shell script that sets up the desired call.

The type
.I iso9660
is the default.  If no
.B \-t
option is given, or if the
.B auto
type is specified, the superblock is probed for the filesystem type
.RI ( adfs ,
.IR bfs ,
.IR cramfs ,
.IR ext ,
.IR ext2 ,
.IR ext3 ,
.IR hfs ,
.IR hpfs ,
.IR iso9660 ,
.IR jfs ,
.IR minix ,
.IR ntfs ,
.IR qnx4 ,
.IR reiserfs ,
.IR romfs ,
.IR udf ,
.IR ufs ,
.IR vxfs ,
.IR xfs ,
.IR xiafs
are supported).
If this probe fails, mount will try to read the file
.IR /etc/filesystems ,
or, if that does not exist,
.IR /proc/filesystems .
All of the filesystem types listed there will be tried,
except for those that are labeled "nodev" (e.g.,
.IR devpts ,
.I proc
and
.IR nfs ).
If
.I /etc/filesystems
ends in a line with a single * only, mount will read
.I /proc/filesystems
afterwards.

The
.B auto
type may be useful for user-mounted floppies.
Creating a file
.I /etc/filesystems
can be useful to change the probe order (e.g., to try vfat before msdos)
or if you use a kernel module autoloader.
Warning: the probing uses a heuristic (the presence of appropriate `magic'),
and could recognize the wrong filesystem type, possibly with catastrophic
consequences. If your data is valuable, don't ask
.B mount
to guess.

More than one type may be specified in a comma separated
list.  The list of file system types can be prefixed with
.B no
to specify the file system types on which no action should be taken.
(This can be meaningful with the
.B \-a
option.)

For example, the command:
.RS
.RS
.B "mount \-a \-t nomsdos,ext"
.RE
mounts all file systems except those of type
.I msdos
and
.IR ext .
.RE
.TP
.B \-O
Used in conjunction with
.BR \-a ,
to limit the set of filesystems to which the
.B \-a
is applied.  Like
.B \-t
in this regard except that it is useless except in the context of
.BR \-a .
For example, the command:
.RS
.RS
.B "mount \-a \-O no_netdev"
.RE
mounts all file systems except those which have the option
.I _netdev
specified in the options field in the
.I /etc/fstab
file.

It is different from
.B \-t
in that each option is matched exactly; a leading
.B no
at the beginning of one option does not negate the rest.

The
.B \-t
and
.B \-O
options are cumulative in effect; that is, the command
.RS
.B "mount \-a \-t ext2 \-O _netdev"
.RE
mounts all ext2 filesystems with the _netdev option, not all filesystems
that are either ext2 or have the _netdev option specified.
.RE
.TP
.B \-o
Options are specified with a
.B \-o
flag followed by a comma separated string of options.
Some of these options are only useful when they appear in the
.I /etc/fstab
file.  The following options apply to any file system that is being
mounted (but not every file system actually honors them - e.g., the
.B sync
option today has effect only for ext2, ext3 and ufs):
.RS
.TP
.B async
All I/O to the file system should be done asynchronously.
.TP
.B atime
Update inode access time for each access. This is the default.
.TP
.B auto
Can be mounted with the
.B \-a
option.
.TP
.B defaults
Use default options:
.BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async.
.TP
.B dev
Interpret character or block special devices on the file system.
.TP
.B exec
Permit execution of binaries.
.TP
.B _netdev
The filesystem resides on a device that requires network access
(used to prevent the system from attempting to mount these filesystems
until the network has been enabled on the system).
.TP
.B noatime
Do not update inode access times on this file system (e.g, for faster
access on the news spool to speed up news servers).
.TP
.B noauto
Can only be mounted explicitly (i.e., the
.B \-a
option will not cause the file system to be mounted).
.TP
.B nodev
Do not interpret character or block special devices on the file
system.
.TP
.B noexec
Do not allow execution of any binaries on the mounted file system.
This option might be useful for a server that has file systems containing
binaries for architectures other than its own.
.TP
.B nosuid
Do not allow set-user-identifier or set-group-identifier bits to take
effect. (This seems safe, but is in fact rather unsafe if you have
suidperl(1) installed.)
.TP
.B nouser
Forbid an ordinary (i.e., non-root) user to mount the file system.
This is the default.
.TP
.B remount
Attempt to remount an already-mounted file system.  This is commonly
used to change the mount flags for a file system, especially to make a
readonly file system writeable. It does not change device or mount point.
.TP
.B ro
Mount the file system read-only.
.TP
.B rw
Mount the file system read-write.
.TP
.B suid
Allow set-user-identifier or set-group-identifier bits to take
effect.
.TP
.B sync
All I/O to the file system should be done synchronously.
.TP
.B dirsync
All directory updates within the file system should be done synchronously.
This affects the following system calls: creat, link, unlink, symlink,
mkdir, rmdir, mknod and rename.
.TP
.B user
Allow an ordinary user to mount the file system.
The name of the mounting user is written to mtab so that he can unmount
the file system again.
This option implies the options
.BR noexec ", " nosuid ", and " nodev
(unless overridden by subsequent options, as in the option line
.BR user,exec,dev,suid ).
.TP
.B users
Allow every user to mount and unmount the file system.
This option implies the options
.BR noexec ", " nosuid ", and " nodev
(unless overridden by subsequent options, as in the option line
.BR users,exec,dev,suid ).
.RE
.TP
.B \-\-bind
Remount a subtree somewhere else (so that its contents are available
in both places). See above.
.TP
.B \-\-move
Move a subtree to some other place. See above.

.SH "FILESYSTEM SPECIFIC MOUNT OPTIONS"
The following options apply only to certain file systems.
We sort them by file system. They all follow the
.B \-o
flag.
.SH "Mount options for adfs"
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
Set the owner and group of the files in the file system (default: uid=gid=0).
.TP
\fBownmask=\fP\fIvalue\fP and \fBothmask=\fP\fIvalue\fP
Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
respectively (default: 0700 and 0077, respectively).
See also
.IR /usr/src/linux/Documentation/filesystems/adfs.txt .
.SH "Mount options for affs"
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
Set the owner and group of the root of the file system (default: uid=gid=0,
but with option
.B uid
or
.B gid
without specified value, the uid and gid of the current process are taken).
.TP
\fBsetuid=\fP\fIvalue\fP and \fBsetgid=\fP\fIvalue\fP
Set the owner and group of all files.
.TP
.BI mode= value
Set the mode of all files to
.IR value " & 0777"
disregarding the original permissions.
Add search permission to directories that have read permission.
The value is given in octal.
.TP
.B protect
Do not allow any changes to the protection bits on the file system.
.TP
.B usemp
Set uid and gid of the root of the file system to the uid and gid
of the mount point upon the first sync or umount, and then
clear this option. Strange...
.TP
.B verbose
Print an informational message for each successful mount.
.TP
.BI prefix= string
Prefix used before volume name, when following a link.
.TP
.BI volume= string
Prefix (of length at most 30) used before '/' when following a symbolic link.
.TP
.BI reserved= value
(Default: 2.) Number of unused blocks at the start of the device.
.TP
.BI root= value
Give explicitly the location of the root block.
.TP
.BI bs= value
Give blocksize. Allowed values are 512, 1024, 2048, 4096.
.TP
.BR grpquota " / " noquota " / " quota " / " usrquota
These options are accepted but ignored.
(However, quota utilities may react to such strings in
.IR /etc/fstab .)

.SH "Mount options for coherent"
None.

.SH "Mount options for devpts"
The devpts file system is a pseudo file system, traditionally mounted on
.IR /dev/pts .
In order to acquire a pseudo terminal, a process opens
.IR /dev/ptmx ;
the number of the pseudo terminal is then made available to the process
and the pseudo terminal slave can be accessed as
.IR /dev/pts/ <number>.
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
This sets the owner or the group of newly created PTYs to
the specified values. When nothing is specified, they will
be set to the UID and GID of the creating process.
For example, if there is a tty group with GID 5, then
.B gid=5
will cause newly created PTYs to belong to the tty group.
.TP
.BI mode= value
Set the mode of newly created PTYs to the specified value.
The default is 0600.
A value of 
.B mode=620
and 
.B gid=5
makes "mesg y" the default on newly created PTYs.

.SH "Mount options for ext"
None.
Note that the `ext' file system is obsolete. Don't use it.
Since Linux version 2.1.21 extfs is no longer part of the kernel source.

.SH "Mount options for ext2"
The `ext2' file system is the standard Linux file system.
Due to a kernel bug, it may be mounted with random mount options
(fixed in Linux 2.0.4).
.TP
.BR bsddf " / " minixdf
Set the behaviour for the
.I statfs
system call. The
.B minixdf
behaviour is to return in the
.I f_blocks
field the total number of blocks of the file system, while the
.B bsddf
behaviour (which is the default) is to subtract the overhead blocks
used by the ext2 file system and not available for file storage. Thus
.RE
.nf

% mount /k -o minixdf; df /k; umount /k
Filesystem   1024-blocks  Used Available Capacity Mounted on
/dev/sda6      2630655   86954  2412169      3%   /k
% mount /k -o bsddf; df /k; umount /k
Filesystem   1024-blocks  Used Available Capacity Mounted on
/dev/sda6      2543714      13  2412169      0%   /k

.fi
(Note that this example shows that one can add command line options
to the options given in
.IR /etc/fstab .)

.TP
.BR check " / " check=normal " / " check=strict
Set checking level. When at least one of these options is set (and
.B check=normal
is set by default) the inodes and blocks bitmaps are checked upon mount
(which can take half a minute or so on a big disk, and is rather useless).
With strict checking, block deallocation checks that the block to free
is in the data zone.
.TP
.BR check=none " / " nocheck
No checking is done. This is fast. Recent kernels do not have a
check option anymore - checking with
.BR e2fsck (8)
is more meaningful.
.TP
.B debug
Print debugging info upon each (re)mount.
.TP
.BR errors=continue " / " errors=remount-ro " / " errors=panic
Define the behaviour when an error is encountered.
(Either ignore errors and just mark the file system erroneous and continue,
or remount the file system read-only, or panic and halt the system.)
The default is set in the filesystem superblock, and can be
changed using
.BR tune2fs (8).
.TP
.BR grpid " or " bsdgroups " / " nogrpid " or " sysvgroups
These options define what group id a newly created file gets.
When
.BR grpid
is set, it takes the group id of the directory in which it is created;
otherwise (the default) it takes the fsgid of the current process, unless
the directory has the setgid bit set, in which case it takes the gid
from the parent directory, and also gets the setgid bit set
if it is a directory itself.
.TP
\fBresgid=\fP\fIn\fP and \fBresuid=\fP\fIn\fP
The ext2 file system reserves a certain percentage of the available
space (by default 5%, see
.BR mke2fs (8)
and
.BR tune2fs (8)).
These options determine who can use the reserved blocks.
(Roughly: whoever has the specified uid, or belongs to the specified group.)
.TP
.BI sb= n
Instead of block 1, use block
.I n
as superblock. This could be useful when the filesystem has been damaged.
(Earlier, copies of the superblock would be made every 8192 blocks: in
block 1, 8193, 16385, ... (and one got hundreds or even thousands
of copies on a big filesystem). Since version 1.08,
.B mke2fs
has a \-s (sparse superblock) option to reduce the number of backup
superblocks, and since version 1.15 this is the default. Note
that this may mean that ext2 filesystems created by a recent
.B mke2fs
cannot be mounted r/w under Linux 2.0.*.)
The block number here uses 1k units. Thus, if you want to use logical
block 32768 on a filesystem with 4k blocks, use "sb=131072".
.TP
.BR grpquota " / " noquota " / " quota " / " usrquota
These options are accepted but ignored.

.TP
.BR nouid32
Disables 32-bit UIDs and GIDs.  This is for interoperability with older
kernels which only store and expect 16-bit values.


.SH "Mount options for ext3"
The `ext3' file system is version of the ext2 file system which has been
enhanced with journalling.  It supports the same options as ext2 as
well as the following additions:
.\" .TP
.\" .BR abort
.\" Mount the file system in abort mode, as if a fatal error has occurred.
.TP
.BR journal=update
Update the ext3 file system's journal to the current format.
.TP
.BR journal=inum
When a journal already exists, this option is ignored. Otherwise, it
specifies the number of the inode which will represent the ext3 file system's
journal file;  ext3 will create a new journal, overwriting the old contents
of the file whose inode number is
.IR inum .
.TP
.BR noload
Do not load the ext3 file system's journal on mounting.
.TP
.BR data=journal " / " data=ordered " / " data=writeback
Specifies the journalling mode for file data.  Metadata is always journaled.
.RS
.TP
.B journal
All data is committed into the journal prior to being written into the
main file system.
.TP
.B ordered
This is the default mode.  All data is forced directly out to the main file
system prior to its metadata being committed to the journal.
.TP
.B writeback
Data ordering is not preserved - data may be written into the main
file system after its metadata has been committed to the journal.
This is rumoured to be the highest-throughput option.  It guarantees
internal file system integrity, however it can allow old data to appear
in files after a crash and journal recovery.
 
.SH "Mount options for fat"
(Note:
.I fat
is not a separate filesystem, but a common part of the
.IR msdos ,
.I umsdos
and
.I vfat
filesystems.)
.TP
.BR blocksize=512 " / " blocksize=1024 " / " blocksize=2048
Set blocksize (default 512).
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
Set the owner and group of all files. (Default: the uid and gid
of the current process.)
.TP
.BI umask= value
Set the umask (the bitmask of the permissions that are
.B not
present). The default is the umask of the current process.
The value is given in octal.
.TP
.BI dmask= value
Set the umask applied to directories only.
The default is the umask of the current process.
The value is given in octal. Present since 2.5.43.
.TP
.BI fmask= value
Set the umask applied to regular files only.
The default is the umask of the current process.
The value is given in octal. Present since 2.5.43.
.TP
.BI check= value 
Three different levels of pickyness can be chosen:
.RS
.TP
.B r[elaxed]
Upper and lower case are accepted and equivalent, long name parts are
truncated (e.g.
.I verylongname.foobar
becomes
.IR verylong.foo ),
leading and embedded spaces are accepted in each name part (name and extension).
.TP
.B n[ormal]
Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
rejected.  This is the default.
.TP
.B s[trict]
Like "normal", but names may not contain long parts and special characters
that are sometimes used on Linux, but are not accepted by MS-DOS are
rejected. (+, =, spaces, etc.)
.RE
.TP
.BI codepage= value
Sets the codepage for converting to shortname characters on FAT
and VFAT filesystems. By default, codepage 437 is used.
.TP
.BR conv=b[inary] " / " conv=t[ext] " / " conv=a[uto]
The
.I fat
file system can perform CRLF<-->NL (MS-DOS text format to UNIX text
format) conversion in the kernel. The following conversion modes are
available:
.RS
.TP
.B binary
no translation is performed.  This is the default.
.TP
.B text
CRLF<-->NL translation is performed on all files.
.TP
.B auto
CRLF<-->NL translation is performed on all files that don't have a
"well-known binary" extension. The list of known extensions can be found at
the beginning of
.I fs/fat/misc.c
(as of 2.0, the list is: exe, com, bin, app, sys, drv, ovl, ovr, obj,
lib, dll, pif, arc, zip, lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz,
gz, tgz, deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl, dvi).
.PP
Programs that do computed lseeks won't like in-kernel text conversion.
Several people have had their data ruined by this translation. Beware!

For file systems mounted in binary mode, a conversion tool
(fromdos/todos) is available.
.RE
.TP
.BI cvf_format= module
Forces the driver to use the CVF (Compressed Volume File) module
.RI cvf_ module
instead of auto-detection. If the kernel supports kmod, the
cvf_format=xxx option also controls on-demand CVF module loading.
.TP
.BI cvf_option= option
Option passed to the CVF module.
.TP
.B debug
Turn on the
.I debug
flag.  A version string and a list of file system parameters will be
printed (these data are also printed if the parameters appear to be
inconsistent).
.TP
.BR fat=12 " / " fat=16 " / " fat=32
Specify a 12, 16 or 32 bit fat.  This overrides
the automatic FAT type detection routine.  Use with caution!
.TP
.BI iocharset= value
Character set to use for converting between 8 bit characters
and 16 bit Unicode characters. The default is iso8859-1.
Long filenames are stored on disk in Unicode format.
.TP
.B quiet
Turn on the
.I quiet
flag.  Attempts to chown or chmod files do not return errors,
although they fail. Use with caution!
.TP
.B "sys_immutable, showexec, dots, nodots, dotsOK=[yes|no]"
Various misguided attempts to force Unix or DOS conventions
onto a FAT file system.

.SH "Mount options for hpfs"
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
Set the owner and group of all files. (Default: the uid and gid
of the current process.)
.TP
.BI umask= value
Set the umask (the bitmask of the permissions that are
.B not
present). The default is the umask of the current process.
The value is given in octal.
.TP
.BR case=lower " / " case=asis
Convert all files names to lower case, or leave them.
(Default:
.BR case=lower .)
.TP
.BR conv=binary " / " conv=text " / " conv=auto
For
.BR conv=text ,
delete some random CRs (in particular, all followed by NL)
when reading a file.
For
.BR conv=auto ,
choose more or less at random between
.BR conv=binary " and " conv=text .
For
.BR conv=binary ,
just read what is in the file. This is the default.
.TP
.B nocheck
Do not abort mounting when certain consistency checks fail.

.SH "Mount options for iso9660"
ISO 9660 is a standard describing a filesystem structure to be used
on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
.I udf
filesystem.)

Normal
.I iso9660
filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename
length), and in addition all characters are in upper case.  Also there is
no field for file ownership, protection, number of links, provision for
block/character devices, etc.

Rock Ridge is an extension to iso9660 that provides all of these unix like
features.  Basically there are extensions to each directory record that
supply all of the additional information, and when Rock Ridge is in use,
the filesystem is indistinguishable from a normal UNIX file system (except
that it is read-only, of course).
.TP
.B norock
Disable the use of Rock Ridge extensions, even if available. Cf.\&
.BR map .
.TP
.B nojoliet
Disable the use of Microsoft Joliet extensions, even if available. Cf.\&
.BR map .
.TP
.BR check=r[elaxed] " / " check=s[trict]
With
.BR check=relaxed ,
a filename is first converted to lower case before doing the lookup.
This is probably only meaningful together with
.B norock
and
.BR map=normal .
(Default:
.BR check=strict .)
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
Give all files in the file system the indicated user or group id,
possibly overriding the information found in the Rock Ridge extensions.
(Default:
.BR uid=0,gid=0 .)
.TP
.BR map=n[ormal] " / " map=o[ff] " / " map=a[corn]
For non-Rock Ridge volumes, normal name translation maps upper
to lower case ASCII, drops a trailing `;1', and converts `;' to `.'.
With
.B map=off
no name translation is done. See
.BR norock .
(Default:
.BR map=normal .)
.B map=acorn
is like
.BR map=normal
but also apply Acorn extensions if present.
.TP
.BI mode= value
For non-Rock Ridge volumes, give all files the indicated mode.
(Default: read permission for everybody.)
Since Linux 2.1.37 one no longer needs to specify the mode in
decimal. (Octal is indicated by a leading 0.)
.TP
.B unhide
Also show hidden and associated files.
.TP
.B block=[512|1024|2048]
Set the block size to the indicated value.
(Default:
.BR block=1024 .)
.TP
.BR conv=a[uto] " / " conv=b[inary] " / " conv=m[text] " / " conv=t[ext]
(Default:
.BR conv=binary .)
Since Linux 1.3.54 this option has no effect anymore.
(And non-binary settings used to be very dangerous,
possibly leading to silent data corruption.)
.TP
.B cruft
If the high byte of the file length contains other garbage,
set this mount option to ignore the high order bits of the file length.
This implies that a file cannot be larger than 16MB.
The `cruft' option is set automatically if the entire CDROM
has a weird size (negative, or more than 800MB). It is also
set when volume sequence numbers other than 0 or 1 are seen.
.TP
.B session=x
Select number of session on multisession CD. (Since 2.3.4.)
.TP
.B sbsector=xxx
Session begins from sector xxx. (Since 2.3.4.)

.SH "Mount options for minix"
None.

.SH "Mount options for msdos"
See mount options for fat.
If the
.I msdos
file system detects an inconsistency, it reports an error and sets the file
system read-only. The file system can be made writeable again by remounting
it.

.SH "Mount options for ncp"
Just like
.IR nfs ", the " ncp
implementation expects a binary argument (a
.IR "struct ncp_mount_data" )
to the mount system call. This argument is constructed by
.BR ncpmount (8)
and the current version of
.B mount
(2.6h) does not know anything about ncp.

.SH "Mount options for nfs"
Instead of a textual option string, parsed by the kernel, the
.I nfs
file system expects a binary argument of type
.IR "struct nfs_mount_data" .
The program
.B mount
itself parses the following options of the form `tag=value',
and puts them in the structure mentioned:
.BI rsize= n,
.BI wsize= n,
.BI timeo= n,
.BI retrans= n,
.BI acregmin= n,
.BI acregmax= n,
.BI acdirmin= n,
.BI acdirmax= n,
.BI actimeo= n,
.BI retry= n,
.BI port= n,
.BI mountport= n,
.BI mounthost= name,
.BI mountprog= n,
.BI mountvers= n,
.BI nfsprog= n,
.BI nfsvers= n,
.BI namlen= n.
The option
.BI addr= n
is accepted but ignored.
Also the following Boolean options, possibly preceded by
.B no
are recognized:
.BR bg ,
.BR fg ,
.BR soft ,
.BR hard ,
.BR intr ,
.BR posix ,
.BR cto ,
.BR ac ,
.BR tcp ,
.BR udp ,
.BR lock .
For details, see
.BR nfs (5).

Especially useful options include
.TP
.B rsize=8192,wsize=8192
This will make your nfs connection faster than with the default
buffer size of 4096. (NFSv2 does not work with larger values of
.B rsize
and
.BR wsize .)
.TP
.B hard
The program accessing a file on a NFS mounted file system will hang
when the server crashes. The process cannot be interrupted or
killed unless you also specify
.BR intr .
When the NFS server is back online the program will continue undisturbed
from where it was. This is probably what you want.
.TP
.B soft
This option allows the kernel to time out if the nfs server is not
responding for some time. The time can be
specified with
.BR timeo=time .
This option might be useful if your nfs server sometimes doesn't respond
or will be rebooted while some process tries to get a file from the server.
Usually it just causes lots of trouble.
.TP
.B nolock
Do not use locking. Do not start lockd.

.SH "Mount options for ntfs"
.TP
.BI iocharset= name
Character set to use when returning file names.
Unlike VFAT, NTFS suppresses names that contain
unconvertible characters.
.TP
.BR utf8
Use UTF-8 for converting file names.
.TP
.B uni_xlate=[0|1|2]
For 0 (or `no' or `false'), do not use escape sequences
for unknown Unicode characters.
For 1 (or `yes' or `true') or 2, use vfat-style 4-byte escape sequences
starting with ":". Here 2 give a little-endian encoding
and 1 a byteswapped bigendian encoding.
.TP
.B posix=[0|1]
If enabled (posix=1), the file system distinguishes between
upper and lower case. The 8.3 alias names are presented as
hard links instead of being suppressed.
.TP
\fBuid=\fP\fIvalue\fP, \fBgid=\fP\fIvalue\fP and \fBumask=\fP\fIvalue\fP
Set the file permission on the filesystem.
The umask value is given in octal.
By default, the files are owned by root and not readable by somebody else.

.SH "Mount options for proc"
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
These options are recognized, but have no effect as far as I can see.

.SH "Mount options for ramfs"
Ramfs is a memory based filesystem. Mount it and you have it. Unmount it
and it is gone. Present since Linux 2.3.99pre4.
There are no mount options.

.SH "Mount options for reiserfs"
Reiserfs is a journaling filesystem.
The reiserfs mount options are more fully described at
.IR http://www.namesys.com/mount-options.html .
.TP
.BR conv
Instructs version 3.6 reiserfs software to mount a version 3.5 file system,
using the 3.6 format for newly created objects. This file system will no
longer be compatible with reiserfs 3.5 tools.
.TP
.BR hash=rupasov " / " hash=tea " / " hash=r5 " / " hash=detect
Choose which hash function reiserfs will use to find files within directories.
.RS
.TP
.B rupasov
A hash invented by Yury Yu. Rupasov.  It is fast and preserves locality,
mapping lexicographically close file names to close hash values.
This option should not be used, as it causes a high probability of hash
collisions. 
.TP
.B tea
A Davis-Meyer function implemented by Jeremy Fitzhardinge.
It uses hash permuting bits in the name.  It gets high randomness
and, therefore, low probability of hash collisions at come CPU cost.
This may be used if EHASHCOLLISION errors are experienced with the r5 hash. 
.TP
.B r5
A modified version of the rupasov hash. It is used by default and is
the best choice unless the file system has huge directories and
unusual file-name patterns. 
.TP
.B detect
Instructs
.IR mount
to detect which hash function is in use by examining
the file system being mounted,  and to write this information into
the reiserfs superblock. This is only useful on the first mount of
an old format file system. 
.RE
.TP
.BR hashed_relocation
Tunes the block allocator. This may provide performance improvements
in some situations. 
.TP
.BR no_unhashed_relocation
Tunes the block allocator. This may provide performance improvements
in some situations.
.TP
.BR noborder
Disable the border allocator algorithm invented by Yury Yu. Rupasov.
This may provide performance improvements in some situations.
.TP
.BR nolog
Disable journalling. This will provide slight performance improvements in
some situations at the cost of losing reiserfs's fast recovery from crashes.
Even with this option turned on, reiserfs still performs all journalling
operations, save for actual writes into its journalling area.  Implementation
of
.IR nolog
is a work in progress.
.TP
.BR notail
By default, reiserfs stores small files and `file tails' directly into its
tree. This confuses some utilities such as
.BR LILO (8) .
This option is used to disable packing of files into the tree. 
.TP
.BR replayonly
Replay the transactions which are in the journal, but do not actually
mount the file system. Mainly used by
.IR reiserfsck .
.TP
.BI resize= number
A remount option which permits online expansion of reiserfs partitions.
Instructs reiserfs to assume that the device has
.I number
blocks.
This option is designed for use with devices which are under logical
volume management (LVM).
There is a special
.I resizer
utility which can be obtained from
.IR ftp://ftp.namesys.com/pub/reiserfsprogs .

.SH "Mount options for romfs"
None.

.SH "Mount options for smbfs"
Just like
.IR nfs ", the " smb
implementation expects a binary argument (a
.IR "struct smb_mount_data" )
to the mount system call. This argument is constructed by
.BR smbmount (8)
and the current version of
.B mount
(2.9w) does not know anything about smb.

.SH "Mount options for sysv"
None.

.SH "Mount options for tmpfs"
The following parameters accept a suffix
.BR k ,
.B m
or
.B g
for Ki, Mi, Gi (binary kilo, mega and giga) and can be changed on remount.
.TP
.BI size= nbytes
Override default size of the filesystem.
The size is given in bytes, and rounded down to entire pages.
The default is half of the memory.
.TP
.B nr_blocks=
Set number of blocks.
.TP
.B nr_inodes=
Set number of inodes.
.TP
.B mode=
Set initial permissions of the root directory.

.SH "Mount options for udf"
udf is the "Universal Disk Format" filesystem defined by the Optical
Storage Technology Association, and is often used for DVD-ROM.
See also
.IR iso9660 .
.TP
.B gid=
Set the default group.
.TP
.B umask=
Set the default umask.
The value is given in octal.
.TP
.B uid=
Set the default user.
.TP
.B unhide
Show otherwise hidden files.
.TP
.B undelete
Show deleted files in lists.
.TP
.B strict
Set strict conformance (unused).
.TP
.B utf8
(unused).
.TP
.B iocharset
(unused).
.TP
.B bs=
Set the block size. (May not work unless 2048.)
.TP
.B novrs
Skip volume sequence recognition.
.TP
.B session=
Set the CDROM session counting from 0. Default: last session.
.TP
.B anchor=
Override standard anchor location. Default: 256.
.TP
.B volume=
Override the VolumeDesc location. (unused)
.TP
.B partition=
Override the PartitionDesc location. (unused)
.TP
.B lastblock=
Set the last block of the filesystem.
.TP
.B fileset=
Override the fileset block location. (unused)
.TP
.B rootdir=
Override the root directory location. (unused)

.SH "Mount options for ufs"
.TP
.BI ufstype= value
UFS is a file system widely used in different operating systems.
The problem are differences among implementations. Features of some
implementations are undocumented, so its hard to recognize the
type of ufs automatically.
That's why the user must specify the type of ufs by mount option.
Possible values are:
.RS
.TP
.B old
Old format of ufs, this is the default, read only.
(Don't forget to give the \-r option.)
.TP
.B 44bsd
For filesystems created by a BSD-like system (NetBSD,FreeBSD,OpenBSD).
.TP
.B sun
For filesystems created by SunOS or Solaris on Sparc.
.TP
.B sunx86
For filesystems created by Solaris on x86.
.TP
.B nextstep
For filesystems created by NeXTStep (on NeXT station) (currently read only).
.TP
.B nextstep-cd
For NextStep CDROMs (block_size == 2048), read-only.
.TP
.B openstep
For filesystems created by OpenStep (currently read only).
The same filesystem type is also used by Mac OS X.
.RE

.TP
.BI onerror= value
Set behaviour on error:
.RS
.TP
.B panic
If an error is encountered, cause a kernel panic.
.TP
.B [lock|umount|repair]
These mount options don't do anything at present;
when an error is encountered only a console message is printed.
.RE

.SH "Mount options for umsdos"
See mount options for msdos.
The
.B dotsOK
option is explicitly killed by
.IR umsdos .

.SH "Mount options for vfat"
First of all, the mount options for
.I fat
are recognized.
The
.B dotsOK
option is explicitly killed by
.IR vfat .
Furthermore, there are
.TP
.B uni_xlate
Translate unhandled Unicode characters to special escaped sequences.
This lets you backup and restore filenames that are created with any
Unicode characters. Without this option, a '?' is used when no
translation is possible. The escape character is ':' because it is
otherwise illegal on the vfat filesystem. The escape sequence
that gets used, where u is the unicode character,
is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
.TP
.B posix
Allow two files with names that only differ in case.
.TP
.B nonumtail
First try to make a short name without sequence number,
before trying
.IR name~num.ext .
.TP
.B utf8
UTF8 is the filesystem safe 8-bit encoding of Unicode that is used
by the console. It can be be enabled for the filesystem with this option.
If `uni_xlate' gets set, UTF8 gets disabled.
.TP
.B shortname=[lower|win95|winnt|mixed]

Defines the behaviour for creation and display of filenames which fit into
8.3 characters. If a long name for a file exists, it will always be
preferred display. There are four modes:
.RS
.TP
.I lower
Force the short name to lower case upon display; store a long name when 
the short name is not all upper case.
.TP
.I win95
Force the short name to upper case upon display; store a long name when
the short name is not all upper case.
. TP
.I winnt
Display the shortname as is; store a long name when the short name is 
not all lower case or all upper case.
.TP
.I mixed
Display the short name as is; store a long name when the short name is not
all upper case.
.RE

The default is "lower".

.SH "Mount options for xenix"
None.

.SH "Mount options for xfs"
.TP
.BI biosize= size
Sets the preferred buffered I/O size (default size is 64K).
.I size
must be expressed as the logarithm (base2) of the desired I/O size.
Valid values for this option are 14 through 16, inclusive
(i.e. 16K, 32K, and 64K bytes).
On machines with a 4K pagesize, 13 (8K bytes) is also a valid
.IR size .
The preferred buffered I/O size can also be altered on an individual
file basis using the
.BR ioctl (2)
system call.
.TP
.B dmapi " / " xdsm
Enable the DMAPI (Data Management API) event callouts.
.TP
.BI logbufs= value
Set the number of in-memory log buffers.
Valid numbers range from 2-8 inclusive.
The default value is 8 buffers for filesystems with a blocksize of 64K,
4 buffers for filesystems with a blocksize of 32K,
3 buffers for filesystems with a blocksize of 16K,
and 2 buffers for all other configurations.
Increasing the number of buffers may increase performance on
some workloads at the cost of the memory used for the
additional log buffers and their associated control structures.
.TP
.BI logbsize= value
Set the size of each in-memory log buffer.
Valid sizes are 16384 (16K) and 32768 (32K).
The default value for machines with more than 32MB of memory is 32768,
machines with less memory use 16384 by default.
.TP
\fBlogdev=\fP\fIdevice\fP and \fBrtdev=\fP\fIdevice\fP
Use an external log (metadata journal) and/or real-time device.
An XFS filesystem has up to three parts: a data section, a log section,
and a real-time section.
The real-time section is optional, and the log section can be separate
from the data section or contained within it.
Refer to
.BR xfs (5).
.TP
.B noalign
Data allocations will not be aligned at stripe unit boundaries.
.TP
.B noatime
Access timestamps are not updated when a file is read.
.TP
.B norecovery
The filesystem will be mounted without running log recovery.
If the filesystem was not cleanly unmounted, it is likely to
be inconsistent when mounted in
.B norecovery
mode.
Some files or directories may not be accessible because of this.
Filesystems mounted
.B norecovery
must be mounted read-only or the mount will fail.
.TP
.B osyncisdsync
Make writes to files opened with the O_SYNC flag set behave
as if the O_DSYNC flag had been used instead.
This can result in better performance without compromising
data safety.
However if this option is in effect, timestamp updates from
O_SYNC writes can be lost if the system crashes.
.TP
.BR quota " / " usrquota " / " uqnoenforce
User disk quota accounting enabled, and limits (optionally) enforced.
.TP
.BR grpquota " / " gqnoenforce
Group disk quota accounting enabled and limits (optionally) enforced.
.TP
\fBsunit=\fP\fIvalue\fP and \fBswidth=\fP\fIvalue\fP
Used to specify the stripe unit and width for a RAID device or a stripe
volume.
.I value
must be specified in 512-byte block units.
If this option is not specified and the filesystem was made on a stripe
volume or the stripe width or unit were specified for the RAID device at
mkfs time, then the mount system call will restore the value from the
superblock.
For filesystems that are made directly on RAID devices, these options can be
used to override the information in the superblock if the underlying disk
layout changes after the filesystem has been created.
The
.B swidth
option is required if the
.B sunit
option has been specified,
and must be a multiple of the
.B sunit
value.

.SH "Mount options for xiafs"
None. Although nothing is wrong with xiafs, it is not used much,
and is not maintained. Probably one shouldn't use it.
Since Linux version 2.1.21 xiafs is no longer part of the kernel source.

.SH "THE LOOP DEVICE"
One further possible type is a mount via the loop device. For example,
the command

.nf
.B "  mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024"
.fi

will set up the loop device
.I /dev/loop3
to correspond to the file
.IR /tmp/fdimage ,
and then mount this device on
.IR /mnt .
This type of mount knows about three options, namely
.BR loop ", " offset " and " encryption ,
that are really options to
.BR losetup (8).
If no explicit loop device is mentioned
(but just an option `\fB\-o loop\fP' is given), then
.B mount
will try to find some unused loop device and use that.
If you are not so unwise as to make
.I /etc/mtab
a symbolic link to
.I /proc/mounts
then any loop device allocated by
.B mount
will be freed by
.BR umount .
You can also free a loop device by hand, using `losetup -d', see
.BR losetup (8).

.SH RETURN CODES
.B mount
has the following return codes (the bits can be ORed):
.TP
.BR 0
success
.TP
.BR 1
incorrect invocation or permissions
.TP
.BR 2
system error (out of memory, cannot fork, no more loop devices)
.TP
.BR 4
internal
.B mount
bug or missing
.BR nfs
support in
.B mount
.TP
.BR 8
user interrupt
.TP
.BR 16
problems writing or locking /etc/mtab
.TP
.BR 32
mount failure
.TP
.BR 64
some mount succeeded

.SH FILES
.I /etc/fstab
file system table
.br
.I /etc/mtab
table of mounted file systems
.br
.I /etc/mtab~
lock file
.br
.I /etc/mtab.tmp
temporary file
.SH "SEE ALSO"
.BR mount (2),
.BR umount (2),
.BR fstab (5),
.BR umount (8),
.BR swapon (8),
.BR nfs (5),
.BR xfs (5),
.BR e2label (8),
.BR xfs_admin (8),
.BR mountd (8),
.BR nfsd (8),
.BR mke2fs (8),
.BR tune2fs (8),
.BR losetup (8)
.SH BUGS
It is possible for a corrupted file system to cause a crash.
.PP
Some Linux file systems don't support
.B "\-o sync and \-o dirsync"
(the ext2 and ext3 file systems
.I do
support synchronous updates (a la BSD) when mounted with the
.B sync
option).
.PP
The
.B "\-o remount"
may not be able to change mount parameters (all
.IR ext2fs -specific
parameters, except
.BR  sb ,
are changeable with a remount, for example, but you can't change
.B gid
or
.B umask
for the
.IR fatfs ).
.SH HISTORY
A
.B mount
command existed in Version 5 AT&T UNIX.