mount -a [-fFnrsvw] [-t vfstype] [-O optlist] mount [-fnrsvw] [-o options [,...]] device | dir mount [-fnrsvw] [-t vfstype] [-o options] device dir
DESCRIPTION
All files accessible in a Unix system are arranged in one big
tree, the file hierarchy, rooted at
/.
These files can be spread out over several devices. The
mount
command serves to attach the file system found on some device
to the big file tree. Conversely, the
umount(8)
command will detach it again.
The standard form of the
mount
command, is
mount -t type device dir
This tells the kernel to attach the file system found on
device
(which is of type
type)
at the directory
dir.
The previous contents (if any) and owner and mode of
dir
become invisible, and as long as this file system remains mounted,
the pathname
dir
refers to the root of the file system on
device.
Three forms of invocation do not actually mount anything:
mount -h
prints a help message;
mount -V
prints a version string; and just
mount [-l] [-t type]
lists all mounted file systems (of type
type).
The option -l adds the (ext2, ext3 and XFS) labels in this listing.
See below.
Since Linux 2.4.0 it is possible to remount part of the
file hierarchy somewhere else. The call is
mount --bind olddir newdir
After this call the same contents is accessible in two places.
One can also remount a single file (on a single file).
This call attaches only (part of) a single filesystem, not possible
submounts. The entire file hierarchy including submounts is attached
a second place using
mount --rbind olddir newdir
Note that the filesystem mount options will remain the same as those
on the original mount point, and cannot be changed by passing the -o
option along with --bind/--rbind.
Since Linux 2.5.1 it is possible to atomically move a mounted tree
to another place. The call is
mount --move olddir newdir
Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared,
private, slave or unbindable. A shared mount provides ability to create mirrors
of that mount such that mounts and umounts within any of the mirrors propagate
to the other mirror. A slave mount receives propagation from its master, but
any not vice-versa. A private mount carries no propagation abilities. A
unbindable mount is a private mount which cannot cloned through a bind
operation. Detailed semantics is documented in Documentation/sharedsubtree.txt
file in the kernel source tree.
mount --make-shared mountpoint mount --make-slave mountpoint mount --make-private mountpoint mount --make-unbindable mountpoint
The following commands allows one to recursively change the type of all the
mounts under a given mountpoint.
mount --make-rshared mountpoint mount --make-rslave mountpoint mount --make-rprivate mountpoint "mount --make-runbindable mountpoint"
The
proc
file system is not associated with a special device, and when
mounting it, an arbitrary keyword, such as
proc
can be used instead of a device specification.
(The customary choice
none
is less fortunate: the error message `none busy' from
umount
can be confusing.)
Most devices are indicated by a file name (of a block special device), like
/dev/sda1,
but there are other possibilities. For example, in the case of an NFS mount,
device
may look like
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
/etc/fstab
(see
fstab(5)),
may contain lines describing what devices are usually
mounted where, using which options. This file is used in three ways:
(i) The command
mount -a [-t type] [-O optlist]
(usually given in a bootscript) causes all file systems mentioned in
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
noauto
keyword. Adding the
-F
option will make mount fork, so that the
filesystems are mounted simultaneously.
(ii) When mounting a file system mentioned in
fstab,
it suffices to give only the device, or only the mount point.
(iii) Normally, only the superuser can mount file systems.
However, when
fstab
contains the
user
option on a line, anybody can mount the corresponding system.
Thus, given a line
/dev/cdrom /cd iso9660 ro,user,noauto,unhide
any user can mount the iso9660 file system found on his CDROM
using the command
mount /dev/cdrom
or
mount /cd
For more details, see
fstab(5).
Only the user that mounted a filesystem can unmount it again.
If any user should be able to unmount, then use
users
instead of
user
in the
fstab
line.
The
owner
option is similar to the
user
option, with the restriction that the user must be the owner
of the special file. This may be useful e.g. for
/dev/fd
if a login script makes the console user owner of this device.
The
group
option is similar, with the restriction that the user must be
member of the group of the special file.
The programs
mount
and
umount
maintain a list of currently mounted file systems in the file
/etc/mtab.
If no arguments are given to
mount,
this list is printed.
When the
proc
filesystem is mounted (say at
/proc),
the files
/etc/mtab
and
/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
-n
option below). It is possible to replace
/etc/mtab
by a symbolic link to
/proc/mounts,
and especially when you have very large numbers of mounts
things will be much faster with that symlink,
but some information is lost that way, and in particular
working with the loop device will be less convenient,
and using the "user" option will fail.
OPTIONS
The full set of options used by an invocation of
mount
is determined by first extracting the
options for the file system from the
fstab
table, then applying any options specified by the
-o
argument, and finally applying a
-r or -w
option, when present.
Options available for the
mount
command:
-V
Output version.
-h
Print a help message.
-v
Verbose mode.
-a
Mount all filesystems (of the given types) mentioned in
fstab.
-F
(Used in conjunction with
-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
/usr
and
/usr/spool.
-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
-v
flag to determine what the
mount
command is trying to do. It can also be used to add entries for devices
that were mounted earlier with the -n option.
-i
Don't call the /sbin/mount.<filesystem> helper even if it exists.
-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
e2label(8)
utility, or for XFS using
xfs_admin(8),
or for reiserfs using
reiserfstune(8).
-n
Mount without writing in
/etc/mtab.
This is necessary for example when
/etc
is on a read-only file system.
-p num
In case of a loop mount with encryption, read the passphrase from
file descriptor
num
instead of from the terminal.
-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.
-r
Mount the file system read-only. A synonym is
-o ro.
-w
Mount the file system read/write. This is the default. A synonym is
-o rw.
-L label
Mount the partition that has the specified
label.
-U uuid
Mount the partition that has the specified
uuid.
These two options require the file
/proc/partitions
(present since Linux 2.1.116) to exist.
-t vfstype
The argument following the
-t
is used to indicate the file system type. The file system types which are
currently supported include:
adfs,
affs,
autofs,
cifs,
coda,
coherent,
cramfs,
debugfs,
devpts,
efs,
ext,
ext2,
ext3,
hfs,
hpfs,
iso9660,
jfs,
minix,
msdos,
ncpfs,
nfs,
nfs4,
ntfs,
proc,
qnx4,
ramfs,
reiserfs,
romfs,
smbfs,
sysv,
tmpfs,
udf,
ufs,
umsdos,
usbfs,
vfat,
xenix,
xfs,
xiafs.
Note that coherent, sysv and xenix are equivalent and that
xenix
and
coherent
will be removed at some point in the future --- use
sysv
instead. Since kernel version 2.1.21 the types
ext
and
xiafs
do not exist anymore. Earlier,
usbfs
was known as
usbdevfs.
For most types all the
mount
program has to do is issue a simple
mount(2)
system call, and no detailed knowledge of the filesystem type is required.
For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) ad hoc code is
necessary. The nfs ad hoc code is built in, but cifs, 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
/sbin/mount.TYPE
(if that exists) when called with type
TYPE.
Since various versions of the
smbmount
program have different calling conventions,
/sbin/mount.smbfs
may have to be a shell script that sets up the desired call.
If no
-t
option is given, or if the
auto
type is specified, mount will try to guess the desired type.
If mount was compiled with the blkid library, the guessing is done
by this library. Otherwise, mount guesses itself by probing the
superblock; if that does not turn up anything that looks familiar,
mount will try to read the file
/etc/filesystems,
or, if that does not exist,
/proc/filesystems.
All of the filesystem types listed there will be tried,
except for those that are labeled "nodev" (e.g.,
devpts,
proc,
nfs,
and
nfs4).
If
/etc/filesystems
ends in a line with a single * only, mount will read
/proc/filesystems
afterwards.
The
auto
type may be useful for user-mounted floppies.
Creating a file
/etc/filesystems
can be useful to change the probe order (e.g., to try vfat before msdos
or ext3 before ext2) 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
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
no
to specify the file system types on which no action should be taken.
(This can be meaningful with the
-a
option.)
For example, the command:
mount -a -t nomsdos,ext
mounts all file systems except those of type
msdos
and
ext.
-O
Used in conjunction with
-a,
to limit the set of filesystems to which the
-a
is applied. Like
-t
in this regard except that it is useless except in the context of
-a.
For example, the command:
mount -a -O no_netdev
mounts all file systems except those which have the option
_netdev
specified in the options field in the
/etc/fstab
file.
It is different from
-t
in that each option is matched exactly; a leading
no
at the beginning of one option does not negate the rest.
The
-t
and
-O
options are cumulative in effect; that is, the command
mount -a -t ext2 -O _netdev
mounts all ext2 filesystems with the _netdev option, not all filesystems
that are either ext2 or have the _netdev option specified.
-o
Options are specified with a
-o
flag followed by a comma separated string of options.
Some of these options are only useful when they appear in the
/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
sync
option today has effect only for ext2, ext3, fat, vfat and ufs):
async
All I/O to the file system should be done asynchronously.
atime
Update inode access time for each access. This is the default.
auto
Can be mounted with the
-a
option.
defaults
Use default options:
rw, suid, dev, exec, auto, nouser, and async.
dev
Interpret character or block special devices on the file system.
exec
Permit execution of binaries.
group
Allow an ordinary (i.e., non-root) user to mount the file system if one
of his groups matches the group of the device.
This option implies the options
nosuid and nodev
(unless overridden by subsequent options, as in the option line
group,dev,suid).
mand
Allow mandatory locks on this filesystem. See
fcntl(2).
_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).
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).
nodiratime
Do not update directory inode access times on this filesystem.
noauto
Can only be mounted explicitly (i.e., the
-a
option will not cause the file system to be mounted).
nodev
Do not interpret character or block special devices on the file
system.
noexec
Do not allow direct execution of any binaries on the mounted file system.
(Until recently it was possible to run binaries anyway using a command like
/lib/ld*.so /mnt/binary. This trick fails since Linux 2.4.25 / 2.6.0.)
nomand
Do not allow mandatory locks on this filesystem.
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.)
nouser
Forbid an ordinary (i.e., non-root) user to mount the file system.
This is the default.
owner
Allow an ordinary (i.e., non-root) user to mount the file system if he
is the owner of the device.
This option implies the options
nosuid and nodev
(unless overridden by subsequent options, as in the option line
owner,dev,suid).
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.
ro
Mount the file system read-only.
rw
Mount the file system read-write.
suid
Allow set-user-identifier or set-group-identifier bits to take
effect.
sync
All I/O to the file system should be done synchronously. In case of media with limited number of write cycles
(e.g. some flash drives) "sync" may cause life-cycle shortening.
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.
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
noexec, nosuid, and nodev
(unless overridden by subsequent options, as in the option line
user,exec,dev,suid).
users
Allow every user to mount and unmount the file system.
This option implies the options
noexec, nosuid, and nodev
(unless overridden by subsequent options, as in the option line
users,exec,dev,suid).
context=context, fscontext=context and defcontext=context
The
context=
option is useful when mounting filesystems that do not support
extended attributes, such as a floppy or hard disk formatted with VFAT, or
systems that are not normally running under SELinux, such as an ext3 formatted
disk from a non-SELinux workstation. You can also use
context=
on filesystems you do not trust, such as a floppy. It also helps in compatibility with
xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where
xattrs are supported, you can save time not having to label every file by
assigning the entire disk one security context.
A commonly used option for removable media is
context=system_u:object_r:removable_t.
Two other options are
fscontext=
and
defcontext=,
both of which are mutually exclusive of the context option. This means you
can use fscontext and defcontext with each other, but neither can be used with
context.
The
fscontext=
option works for all filesystems, regardless of their xattr
support. The fscontext option sets the overarching filesystem label to a
specific security context. This filesystem label is separate from the
individual labels on the files. It represents the entire filesystem for
certain kinds of permission checks, such as during mount or file creation.
Individual file labels are still obtained from the xattrs on the files
themselves. The context option actually sets the aggregate context that
fscontext provides, in addition to supplying the same label for individual
files.
You can set the default security context for unlabeled files using
defcontext=
option. This overrides the value set for unlabeled files in the policy and requires a
file system that supports xattr labeling.
Remount a subtree somewhere else (so that its contents are available
in both places). See above.
--move
Move a subtree to some other place. See above.
FILESYSTEM SPECIFIC MOUNT OPTIONS
The following options apply only to certain file systems.
We sort them by file system. They all follow the
-o
flag.
What options are supported depends a bit on the running kernel.
More info may be found in the kernel source subdirectory
Documentation/filesystems.
Mount options for adfs
uid=value and gid=value
Set the owner and group of the files in the file system (default: uid=gid=0).
ownmask=value and othmask=value
Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
respectively (default: 0700 and 0077, respectively).
See also
/usr/src/linux/Documentation/filesystems/adfs.txt.
Mount options for affs
uid=value and gid=value
Set the owner and group of the root of the file system (default: uid=gid=0,
but with option
uid
or
gid
without specified value, the uid and gid of the current process are taken).
setuid=value and setgid=value
Set the owner and group of all files.
mode=value
Set the mode of all files to
value & 0777
disregarding the original permissions.
Add search permission to directories that have read permission.
The value is given in octal.
protect
Do not allow any changes to the protection bits on the file system.
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...
verbose
Print an informational message for each successful mount.
prefix=string
Prefix used before volume name, when following a link.
volume=string
Prefix (of length at most 30) used before '/' when following a symbolic link.
reserved=value
(Default: 2.) Number of unused blocks at the start of the device.
root=value
Give explicitly the location of the root block.
bs=value
Give blocksize. Allowed values are 512, 1024, 2048, 4096.
grpquota / noquota / quota / usrquota
These options are accepted but ignored.
(However, quota utilities may react to such strings in
/etc/fstab.)
Mount options for cifs
See the options section of the
mount.cifs(8)
man page (cifs-mount package must be installed).
Mount options for cifs
Just like
nfs or smbfs
implementation expects a binary argument
to the mount system call. This argument is constructed by
mount.cifs(8)
and the current version of
mount
(2.12) does not know anything about cifs.
Mount options for coherent
None.
Mount options for debugfs
The debugfs file system is a pseudo file system, traditionally mounted on
/sys/kernel/debug.
There are no mount options.
Mount options for devpts
The devpts file system is a pseudo file system, traditionally mounted on
/dev/pts.
In order to acquire a pseudo terminal, a process opens
/dev/ptmx;
the number of the pseudo terminal is then made available to the process
and the pseudo terminal slave can be accessed as
/dev/pts/<number>.
uid=value and gid=value
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
gid=5
will cause newly created PTYs to belong to the tty group.
mode=value
Set the mode of newly created PTYs to the specified value.
The default is 0600.
A value of
mode=620
and
gid=5
makes "mesg y" the default on newly created PTYs.
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.
Mount options for ext2
The `ext2' file system is the standard Linux file system.
Since Linux 2.5.46, for most mount options the default
is determined by the filesystem superblock. Set them with
tune2fs(8).
acl / noacl
Support POSIX Access Control Lists (or not).
bsddf / minixdf
Set the behaviour for the
statfs
system call. The
minixdf
behaviour is to return in the
f_blocks
field the total number of blocks of the file system, while the
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
% 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
(Note that this example shows that one can add command line options
to the options given in
/etc/fstab.)
check=none / nocheck
No checking is done at mount time. This is the default. This is fast.
It is wise to invoke
e2fsck(8)
every now and then, e.g. at boot time.
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
tune2fs(8).
grpid or bsdgroups / nogrpid or sysvgroups
These options define what group id a newly created file gets.
When
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.
grpquota / noquota / quota / usrquota
These options are accepted but ignored.
nobh
Do not attach buffer_heads to file pagecache. (Since 2.5.49.)
nouid32
Disables 32-bit UIDs and GIDs. This is for interoperability with older
kernels which only store and expect 16-bit values.
oldalloc or orlov
Use old allocator or Orlov allocator for new inodes. Orlov is default.
resgid=n and resuid=n
The ext2 file system reserves a certain percentage of the available
space (by default 5%, see
mke2fs(8)
and
tune2fs(8)).
These options determine who can use the reserved blocks.
(Roughly: whoever has the specified uid, or belongs to the specified group.)
sb=n
Instead of block 1, use block
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 thousands of copies on
a big filesystem). Since version 1.08,
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
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".
user_xattr / nouser_xattr
Support "user." extended attributes (or not).
Mount options for ext3
The `ext3' file system is a 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:
journal=update
Update the ext3 file system's journal to the current format.
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
inum.
noload
Do not load the ext3 file system's journal on mounting.
data=journal / data=ordered / data=writeback
Specifies the journalling mode for file data. Metadata is always journaled.
To use modes other than
ordered
on the root file system, pass the mode to the kernel as boot parameter, e.g.
rootflags=data=journal.
journal
All data is committed into the journal prior to being written into the
main file system.
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.
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.
commit=nrsec
Sync all data and metadata every
nrsec
seconds. The default value is 5 seconds. Zero means default.
Mount options for fat
(Note:
fat
is not a separate filesystem, but a common part of the
msdos,
umsdos
and
vfat
filesystems.)
blocksize=512 / blocksize=1024 / blocksize=2048
Set blocksize (default 512).
uid=value and gid=value
Set the owner and group of all files.
(Default: the uid and gid of the current process.)
umask=value
Set the umask (the bitmask of the permissions that are
not
present). The default is the umask of the current process.
The value is given in octal.
dmask=value
Set the umask applied to directories only.
The default is the umask of the current process.
The value is given in octal.
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.
check=value
Three different levels of pickyness can be chosen:
r[elaxed]
Upper and lower case are accepted and equivalent, long name parts are
truncated (e.g.
verylongname.foobar
becomes
verylong.foo),
leading and embedded spaces are accepted in each name part (name and extension).
n[ormal]
Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
rejected. This is the default.
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.)
codepage=value
Sets the codepage for converting to shortname characters on FAT
and VFAT filesystems. By default, codepage 437 is used.
conv=b[inary] / conv=t[ext] / conv=a[uto]
The
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:
binary
no translation is performed. This is the default.
text
CRLF<-->NL translation is performed on all files.
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
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).
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.
cvf_format=module
Forces the driver to use the CVF (Compressed Volume File) module
cvf_module
instead of auto-detection. If the kernel supports kmod, the
cvf_format=xxx option also controls on-demand CVF module loading.
cvf_option=option
Option passed to the CVF module.
debug
Turn on the
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).
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!
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.
quiet
Turn on the
quiet
flag. Attempts to chown or chmod files do not return errors,
although they fail. Use with caution!
Various misguided attempts to force Unix or DOS conventions
onto a FAT file system.
Mount options for hfs
creator=cccc, type=cccc
Set the creator/type values as shown by the MacOS finder
used for creating new files. Default values: '????'.
uid=n, gid=n
Set the owner and group of all files.
(Default: the uid and gid of the current process.)
dir_umask=n, file_umask=n, umask=n
Set the umask used for all directories, all regular files, or all
files and directories. Defaults to the umask of the current process.
session=n
Select the CDROM session to mount.
Defaults to leaving that decision to the CDROM driver.
This option will fail with anything but a CDROM as underlying device.
part=n
Select partition number n from the device.
Only makes sense for CDROMS.
Defaults to not parsing the partition table at all.
quiet
Don't complain about invalid mount options.
Mount options for hpfs
uid=value and gid=value
Set the owner and group of all files. (Default: the uid and gid
of the current process.)
umask=value
Set the umask (the bitmask of the permissions that are
not
present). The default is the umask of the current process.
The value is given in octal.
case=lower / case=asis
Convert all files names to lower case, or leave them.
(Default:
case=lower.)
conv=binary / conv=text / conv=auto
For
conv=text,
delete some random CRs (in particular, all followed by NL)
when reading a file.
For
conv=auto,
choose more or less at random between
conv=binary and conv=text.
For
conv=binary,
just read what is in the file. This is the default.
nocheck
Do not abort mounting when certain consistency checks fail.
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
udf
filesystem.)
Normal
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).
norock
Disable the use of Rock Ridge extensions, even if available. Cf.
map.
nojoliet
Disable the use of Microsoft Joliet extensions, even if available. Cf.
map.
check=r[elaxed] / check=s[trict]
With
check=relaxed,
a filename is first converted to lower case before doing the lookup.
This is probably only meaningful together with
norock
and
map=normal.
(Default:
check=strict.)
uid=value and gid=value
Give all files in the file system the indicated user or group id,
possibly overriding the information found in the Rock Ridge extensions.
(Default:
uid=0,gid=0.)
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
map=off
no name translation is done. See
norock.
(Default:
map=normal.)
map=acorn
is like
map=normal
but also apply Acorn extensions if present.
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.)
unhide
Also show hidden and associated files.
(If the ordinary files and the associated or hidden files have
the same filenames, this may make the ordinary files inaccessible.)
block=[512|1024|2048]
Set the block size to the indicated value.
(Default:
block=1024.)
(Default:
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.)
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.
session=x
Select number of session on multisession CD. (Since 2.3.4.)
sbsector=xxx
Session begins from sector xxx. (Since 2.3.4.)
The following options are the same as for vfat and specifying them only makes
sense when using discs encoded using Microsoft's Joliet extensions.
iocharset=value
Character set to use for converting 16 bit Unicode characters on CD
to 8 bit characters. The default is iso8859-1.
utf8
Convert 16 bit Unicode characters on CD to UTF-8.
Mount options for jfs
iocharset=name
Character set to use for converting from Unicode to ASCII. The default is
to do no conversion. Use
iocharset=utf8
for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in
the kernel
.config
file.
resize=value
Resize the volume to
value
blocks. JFS only supports growing a volume, not shrinking it. This option
is only valid during a remount, when the volume is mounted read-write. The
resize
keyword with no value will grow the volume to the full size of the partition.
nointegrity
Do not write to the journal. The primary use of this option is to allow
for higher performance when restoring a volume from backup media. The
integrity of the volume is not guaranteed if the system abnormally abends.
integrity
Default. Commit metadata changes to the journal. Use this option to remount
a volume where the
nointegrity
option was previously specified in order to restore normal behavior.
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.)
noquota / quota / usrquota / grpquota
These options are accepted but ignored.
Mount options for minix
None.
Mount options for msdos
See mount options for fat.
If the
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.
Mount options for ncpfs
Just like
nfs, the ncpfs
implementation expects a binary argument (a
struct ncp_mount_data)
to the mount system call. This argument is constructed by
ncpmount(8)
and the current version of
mount
(2.12) does not know anything about ncpfs.
Mount options for nfs
Instead of a textual option string, parsed by the kernel, the
nfs
file system expects a binary argument of type
struct nfs_mount_data.
The program
mount
itself parses the following options of the form `tag=value',
and puts them in the structure mentioned:
rsize=n,wsize=n,timeo=n,retrans=n,acregmin=n,acregmax=n,acdirmin=n,acdirmax=n,actimeo=n,retry=n,port=n,mountport=n,mounthost=name,mountprog=n,mountvers=n,nfsprog=n,nfsvers=n,namlen=n.
The option
addr=n
is accepted but ignored.
Also the following Boolean options, possibly preceded by
no
are recognized:
bg,
fg,
soft,
hard,
intr,
posix,
cto,
ac,
tcp,
udp,
lock.
For details, see
nfs(5).
Especially useful options include
rsize=32768,wsize=32768
This causes the NFS client to try to negotiate a buffer size
up to the size specified.
A large buffer size does improve performance, but both the
server and client have to support it.
In the case where one of these does not support the size specified,
the size negotiated will be the largest that both support.
intr
This will allow NFS operations (on hard mounts) to be
interrupted while waiting for a response from the server.
nolock
Do not use locking. Do not start lockd.
Mount options for nfs4
Instead of a textual option string, parsed by the kernel, the
nfs4
file system expects a binary argument of type
struct nfs4_mount_data.
The program
mount
itself parses the following options of the form `tag=value',
and puts them in the structure mentioned:
rsize=n,wsize=n,timeo=n,retrans=n,acregmin=n,acregmax=n,acdirmin=n,acdirmax=n,actimeo=n,retry=n,port=n,proto=n,clientaddr=n,sec=n.
The option
addr=n
is accepted but ignored.
Also the following Boolean options, possibly preceded by
no
are recognized:
bg,
fg,
soft,
hard,
intr,
cto,
ac,
For details, see
nfs(5).
Especially useful options include
rsize=32768,wsize=32768
This causes the NFS4 client to try to negotiate a buffer size
up to the size specified.
A large buffer size does improve performance, but both the
server and client have to support it.
In the case where one of these does not support the size specified,
the size negotiated will be the largest that both support.
intr
This will allow NFS4 operations (on hard mounts) to be
interrupted while waiting for a response from the server.
Mount options for ntfs
iocharset=name
Character set to use when returning file names.
Unlike VFAT, NTFS suppresses names that contain
unconvertible characters. Deprecated.
nls=name
New name for the option earlier called
iocharset.
utf8
Use UTF-8 for converting file names.
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.
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.
uid=value, gid=value and umask=value
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.
Mount options for proc
uid=value and gid=value
These options are recognized, but have no effect as far as I can see.
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.
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.
hash=rupasov / hash=tea / hash=r5 / hash=detect
Choose which hash function reiserfs will use to find files within directories.
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.
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 some CPU cost.
This may be used if EHASHCOLLISION errors are experienced with the r5 hash.
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.
detect
Instructs
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.
hashed_relocation
Tunes the block allocator. This may provide performance improvements
in some situations.
no_unhashed_relocation
Tunes the block allocator. This may provide performance improvements
in some situations.
noborder
Disable the border allocator algorithm invented by Yury Yu. Rupasov.
This may provide performance improvements in some situations.
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
nolog
is a work in progress.
notail
By default, reiserfs stores small files and `file tails' directly into its
tree. This confuses some utilities such as
LILO(8).
This option is used to disable packing of files into the tree.
replayonly
Replay the transactions which are in the journal, but do not actually
mount the file system. Mainly used by
reiserfsck.
resize=number
A remount option which permits online expansion of reiserfs partitions.
Instructs reiserfs to assume that the device has
number
blocks.
This option is designed for use with devices which are under logical
volume management (LVM).
There is a special
resizer
utility which can be obtained from
ftp://ftp.namesys.com/pub/reiserfsprogs.
Mount options for romfs
None.
Mount options for smbfs
Just like
nfs, the smbfs
implementation expects a binary argument (a
struct smb_mount_data)
to the mount system call. This argument is constructed by
smbmount(8)
and the current version of
mount
(2.12) does not know anything about smbfs.
Mount options for sysv
None.
Mount options for tmpfs
The following parameters accept a suffix
k,
m
or
g
for Ki, Mi, Gi (binary kilo, mega and giga) and can be changed on remount.
size=nbytes
Override default maximum size of the filesystem.
The size is given in bytes, and rounded down to entire pages.
The default is half of the memory.
nr_blocks=
Set number of blocks.
nr_inodes=
Set number of inodes.
mode=
Set initial permissions of the root directory.
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
iso9660.
gid=
Set the default group.
umask=
Set the default umask.
The value is given in octal.
uid=
Set the default user.
unhide
Show otherwise hidden files.
undelete
Show deleted files in lists.
nostrict
Unset strict conformance.
iocharset
Set the NLS character set.
bs=
Set the block size. (May not work unless 2048.)
novrs
Skip volume sequence recognition.
session=
Set the CDROM session counting from 0. Default: last session.
anchor=
Override standard anchor location. Default: 256.
volume=
Override the VolumeDesc location. (unused)
partition=
Override the PartitionDesc location. (unused)
lastblock=
Set the last block of the filesystem.
fileset=
Override the fileset block location. (unused)
rootdir=
Override the root directory location. (unused)
Mount options for ufs
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:
old
Old format of ufs, this is the default, read only.
(Don't forget to give the -r option.)
44bsd
For filesystems created by a BSD-like system (NetBSD,FreeBSD,OpenBSD).
sun
For filesystems created by SunOS or Solaris on Sparc.
sunx86
For filesystems created by Solaris on x86.
hp
For filesystems created by HP-UX, read-only.
nextstep
For filesystems created by NeXTStep (on NeXT station) (currently read only).
nextstep-cd
For NextStep CDROMs (block_size == 2048), read-only.
openstep
For filesystems created by OpenStep (currently read only).
The same filesystem type is also used by Mac OS X.
onerror=value
Set behaviour on error:
panic
If an error is encountered, cause a kernel panic.
[lock|umount|repair]
These mount options don't do anything at present;
when an error is encountered only a console message is printed.
Mount options for umsdos
See mount options for msdos.
The
dotsOK
option is explicitly killed by
umsdos.
Mount options for vfat
First of all, the mount options for
fat
are recognized.
The
dotsOK
option is explicitly killed by
vfat.
Furthermore, there are
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).
posix
Allow two files with names that only differ in case.
nonumtail
First try to make a short name without sequence number,
before trying
name~num.ext.
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.
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:
lower
Force the short name to lower case upon display; store a long name when
the short name is not all upper case.
win95
Force the short name to upper case upon display; store a long name when
the short name is not all upper case.
winnt
Display the shortname as is; store a long name when the short name is
not all lower case or all upper case.
mixed
Display the short name as is; store a long name when the short name is not
all upper case.
The default is "lower".
Mount options for usbfs
devuid=uid and devgid=gid and devmode=mode
Set the owner and group and mode of the device files in the usbfs file system
(default: uid=gid=0, mode=0644). The mode is given in octal.
busuid=uid and busgid=gid and busmode=mode
Set the owner and group and mode of the bus directories in the usbfs
file system (default: uid=gid=0, mode=0555). The mode is given in octal.
listuid=uid and listgid=gid and listmode=mode
Set the owner and group and mode of the file
devices
(default: uid=gid=0, mode=0444). The mode is given in octal.
Mount options for xenix
None.
Mount options for xfs
biosize=size
Sets the preferred buffered I/O size (default size is 64K).
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
size.
The preferred buffered I/O size can also be altered on an individual
file basis using the
ioctl(2)
system call.
dmapi / xdsm
Enable the DMAPI (Data Management API) event callouts.
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.
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.
logdev=device and rtdev=device
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
xfs(5).
noalign
Data allocations will not be aligned at stripe unit boundaries.
noatime
Access timestamps are not updated when a file is read.
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
norecovery
mode.
Some files or directories may not be accessible because of this.
Filesystems mounted
norecovery
must be mounted read-only or the mount will fail.
nouuid
Ignore the filesystem uuid. This avoids errors for duplicate uuids.
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.
quota / usrquota / uqnoenforce
User disk quota accounting enabled, and limits (optionally) enforced.
grpquota / gqnoenforce
Group disk quota accounting enabled and limits (optionally) enforced.
sunit=value and swidth=value
Used to specify the stripe unit and width for a RAID device or a stripe
volume.
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
swidth
option is required if the
sunit
option has been specified,
and must be a multiple of the
sunit
value.
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.
THE LOOP DEVICE
One further possible type is a mount via the loop device. For example,
the command
mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024
will set up the loop device
/dev/loop3
to correspond to the file
/tmp/fdimage,
and then mount this device on
/mnt.
This type of mount knows about three options, namely
loop, offset and encryption,
that are really options to
losetup(8).
(These options can be used in addition to those specific
to the filesystem type.)
If no explicit loop device is mentioned
(but just an option `-o loop' is given), then
mount
will try to find some unused loop device and use that.
If you are not so unwise as to make
/etc/mtab
a symbolic link to
/proc/mounts
then any loop device allocated by
mount
will be freed by
umount.
You can also free a loop device by hand, using `losetup -d', see
losetup(8).
RETURN CODES
mount
has the following return codes (the bits can be ORed):
0
success
1
incorrect invocation or permissions
2
system error (out of memory, cannot fork, no more loop devices)
4
internal
mount
bug or missing
nfs
support in
mount
It is possible for a corrupted file system to cause a crash.
Some Linux file systems don't support
-o sync and -o dirsync
(the ext2, ext3, fat and vfat file systems
do
support synchronous updates (a la BSD) when mounted with the
sync
option).
The
-o remount
may not be able to change mount parameters (all
ext2fs-specific
parameters, except
sb,
are changeable with a remount, for example, but you can't change
gid
or
umask
for the
fatfs).
Mount by label or uuid will work only if your devices have the names listed in
/proc/partitions.
In particular, it may well fail if the kernel was compiled with devfs
but devfs is not mounted.
It is possible that files
/etc/mtab
and
/proc/mounts
don't match. The first file is based only on the mount command options, but the
content of the second file also depends on the kernel and others settings (e.g.
remote NFS server. In particular case the mount command may reports unreliable
information about a NFS mount point and the /proc/mounts file usually contains
more reliable information.)
Checking files on NFS filesystem referenced by file descriptors (i.e. the
fcntl
and
ioctl
families of functions) may lead to inconsistent result due to the lack of
consistency check in kernel even if noac is used.
