SYNOPSIS
mount [-lhV]
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 sev-
eral 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.
The listing and help.
Three forms of invocation do not actually mount anything:
mount -h
prints a help message
mount -V
prints a version string
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.
The bind mounts.
Since Linux 2.4.0 it is possible to remount part of the file
hierarchy somewhere else. The call is
mount --bind olddir newdir
or fstab entry is:
/olddir /newdir none bind
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 pos-
sible submounts. The entire file hierarchy including submounts
is attached a second place using
Since Linux 2.6.15 it is possible to mark a mount and its sub-
mounts 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 mas-
ter, but any not vice-versa. A private mount carries no propa-
gation 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 device indication.
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 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.)
The /etc/fstab, /etc/mtab and /proc/mounts files.
The file /etc/fstab (see fstab(5)), may contain lines describing
what devices are usually mounted where, using which options.
The command
mount -a [-t type] [-O optlist]
(usually given in a bootscript) causes all file systems men-
tioned 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 simul-
taneously.
When mounting a file system mentioned in fstab, it suffices to
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.
The non-superuser mounts.
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.
COMMAND LINE OPTIONS
The full set of mount options used by an invocation of mount is deter-
mined by first extracting the mount options for the file system from
the fstab table, then applying any options specified by the -o argu-
ment, and finally applying a -r or -w option, when present.
Command line 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
mount, this check is done by kernel).
-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 exam-
ple 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.
Note that, depending on the filesystem type, state and kernel
behavior, the system may still write to the device. For example,
Ext3 will replay its journal if the filesystem is dirty. To pre-
vent this kind of write access, you may want to set the block
device to read-only mode, see command blockdev(8).
-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 sys-
tem type. The file system types which are currently supported
include: adfs, affs, autofs, cifs, coda, coherent, cramfs,
debugfs, devpts, efs, ext, ext2, ext3, hfs, hfsplus, 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. Note, the real list of
all supported filesystems depends on your kernel.
If no -t option is given, or if the auto type is specified,
mount will try to guess the desired type. Mount uses the blkid
or volume_id library for guessing the filesystem type; 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 and nfs). 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 rec-
ognize 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 com-
mand:
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 lead-
ing 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 filesys-
tems that are either ext2 or have the _netdev option specified.
-o Options are specified with a -o flag followed by a comma sepa-
rated string of options. For example:
mount LABEL=mydisk -o noatime,nouser
For more details, see FILESYSTEM INDEPENDENT MOUNT OPTIONS and
FILESYSTEM SPECIFIC MOUNT OPTIONS sections.
FILESYSTEM INDEPENDENT MOUNT OPTIONS
Some of these options are only useful when they appear in the
/etc/fstab file.
Some of these options could be enabled or disabled by default in the
system kernel. To check the current setting see the options in
/proc/mounts.
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. (See
also the sync option.)
atime Update inode access time for each access. This is the default.
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).
auto Can be mounted with the -a option.
noauto Can only be mounted explicitly (i.e., the -a option will not
cause the file system to be mounted).
context=context, fscontext=context, defcontext=context and rootcon-
text=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 con-
text.
A commonly used option for removable media is context=sys-
tem_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
inode of a FS being mounted before that FS or inode because vis-
able to userspace. This was found to be useful for things like
stateless linux.
For more details, see selinux(8)
defaults
Use default options: rw, suid, dev, exec, auto, nouser, and
async.
dev Interpret character or block special devices on the file system.
nodev Do not interpret character or block special devices on the file
system.
diratime
Update directory inode access times on this filesystem. This is
the default.
nodiratime
Do not update directory inode access times on this filesystem.
dirsync
All directory updates within the file system should be done syn-
chronously. This affects the following system calls: creat,
link, unlink, symlink, mkdir, rmdir, mknod and rename.
exec Permit execution of binaries.
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.)
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).
encryption
Specifies an encryption algorithm to use. Used in conjunction
with the loop option.
keybits
Specifies the key size to use for an encryption algorithm. Used
in conjunction with the loop and encryption options. nofail Do
not report errors for this device if it does not exist. iver-
sion Every time the inode is modified, the i_version field will
be incremented.
noiversion
Do not increment the i_version inode field.
Update inode access times relative to modify or change time.
Access time is only updated if the previous access time was ear-
lier than the current modify or change time. (Similar to noat-
ime, but doesn't break mutt or other applications that need to
know if a file has been read since the last time it was modi-
fied.)
norelatime
Do not use relatime feature (e.g, for systems where the feature
is enabled by default, for more details see mount options in
/proc/mounts).
suid Allow set-user-identifier or set-group-identifier bits to take
effect.
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.)
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 com-
monly used to change the mount flags for a file system, espe-
cially to make a readonly file system writeable. It does not
change device or mount point.
The remount functionality follows the standard way how the mount
command works with options from fstab. It means the mount com-
mand doesn't read fstab (or mtab) only when a device and dir are
fully specified.
mount -o remount,rw /dev/foo /dir
After this call all old mount options are replaced and arbitrary
stuff from fstab is ignored, except the loop= option which is
internally generated and maintained by the mount command.
mount -o remount,rw /dir
After this call mount reads fstab (or mtab) and merges these
options with options from command line ( -o ).
ro Mount the file system read-only.
rw Mount the file system read-write.
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.
users,exec,dev,suid).
--bind 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 Documenta-
tion/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, respec-
tively). See also /usr/src/linux/Documentation/filesys-
tems/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 orig-
inal 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 sys-
tem.
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
bs=value
Give blocksize. Allowed values are 512, 1024, 2048, 4096.
grpquota / noquota / quota / usrquota
These options are accepted but ignored. (However, quota utili-
ties may react to such strings in /etc/fstab.)
Mount options for cifs
See the options section of the mount.cifs(8) man page (smbfs package
must be installed).
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).
/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.
debug Print debugging info upon each (re)mount.
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 con-
tinue, 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 avail-
able 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,
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. Other-
wise, 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 commit-
ted 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.
user_xattr
Enable Extended User Attributes. See the attr(5) manual page.
acl Enable POSIX Access Control Lists. See the acl(5) manual page.
Mount options for fat
(Note: fat is not a separate filesystem, but a common part of 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.
allow_utime=value
This option controls the permission check of mtime/atime.
20 If current process is in group of file's group ID, you
can change timestamp.
2 Other users can change timestamp.
The default is set from `dmask' option. (If the directory is
writable, utime(2) is also allowed. I.e. ~dmask & 022)
Normally utime(2) checks current process is owner of the file,
or it has CAP_FOWNER capability. But FAT filesystem doesn't
have uid/gid on disk, so normal check is too unflexible. With
this option you can relax it.
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:
Programs that do computed lseeks won't like in-kernel text con-
version. 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 mod-
ule 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 file-
names are stored on disk in Unicode format.
tz=UTC This option disables the conversion of timestamps between local
time (as used by Windows on FAT) and UTC (which Linux uses
internally). This is particuluarly useful when mounting devices
(like digital cameras) that are set to UTC in order to avoid the
pitfalls of local time.
quiet Turn on the quiet flag. Attempts to chown or chmod files do not
return errors, although they fail. Use with caution!
showexec
If set, the execute permission bits of the file will be allowed
only if the extension part of the name is .EXE, .COM, or .BAT.
Not set by default.
sys_immutable
If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag
on Linux. Not set by default.
flush If set, the filesystem will try to flush to disk more early than
normal. Not set by default.
usefree
Use the "free clusters" value stored on FSINFO. It'll be used to
determine number of free clusters without scanning disk. But
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 any-
thing 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 fol-
lowed 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,
Disable the use of Microsoft Joliet extensions, even if avail-
able. 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.)
conv=a[uto] / conv=b[inary] / conv=m[text] / conv=t[ext]
(Default: conv=binary.) Since Linux 1.3.54 this option has no
effect anymore. (And non-binary settings used to be very dan-
gerous, 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 exten-
sions.
iocharset=value
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 key-
word 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 pre-
viously specified in order to restore normal behavior.
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 con-
tinue, 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 incon-
sistency, 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 con-
structed by ncpmount(8) and the current version of mount (2.12) does
not know anything about ncpfs.
Mount options for nfs and nfs4
See the options section of the nfs(5) man page (nfs-common package must
be installed).
The nfs and nfs4 implementation expects a binary argument (a struct
nfs_mount_data) to the mount system call. This argument is constructed
by mount.nfs(8) and the current version of mount (2.13) does not know
anything about nfs and nfs4.
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.
Mount options for reiserfs
Reiserfs is a journaling filesystem.
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.
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 pre-
serves 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.
Tunes the block allocator. This may provide performance improve-
ments in some situations.
no_unhashed_relocation
Tunes the block allocator. This may provide performance improve-
ments in some situations.
noborder
Disable the border allocator algorithm invented by Yury Yu.
Rupasov. This may provide performance improvements in some sit-
uations.
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 par-
titions. Instructs reiserfs to assume that the device has num-
ber 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.
user_xattr
Enable Extended User Attributes. See the attr(5) manual page.
acl Enable POSIX Access Control Lists. See the acl(5) manual page.
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 con-
structed by smbmount(8) and the current version of mount (2.12) does
not know anything about smbfs.
Mount options for sysv
nr_blocks=
The same as size, but in blocks of PAGE_CACHE_SIZE
nr_inodes=
The maximum number of inodes for this instance. The default is
half of the number of your physical RAM pages, or (on a machine
with highmem) the number of lowmem RAM pages, whichever is the
lower.
The tmpfs mount options for sizing ( size, nr_blocks, and nr_inodes)
accept a suffix k, m or g for Ki, Mi, Gi (binary kilo, mega and giga)
and can be changed on remount.
mode= Set initial permissions of the root directory.
uid= The user id.
gid= The group id.
mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
Set the NUMA memory allocation policy for all files in that
instance (if the kernel CONFIG_NUMA is enabled) - which can be
adjusted on the fly via 'mount -o remount ...'
default
prefers to allocate memory from the local node
prefer:Node
prefers to allocate memory from the given Node
bind:NodeList
allocates memory only from nodes in NodeList
interleave
prefers to allocate from each node in turn
interleave:NodeList
allocates from each node of NodeList in turn.
The NodeList format is a comma-separated list of decimal numbers
and ranges, a range being two hyphen-separated decimal numbers,
the smallest and largest node numbers in the range. For exam-
ple, mpol=bind:0-3,5,7,9-15
Note that trying to mount a tmpfs with an mpol option will fail
if the running kernel does not support NUMA; and will fail if
its nodelist specifies a node which is not online. If your
system relies on that tmpfs being mounted, but from time to time
runs a kernel built without NUMA capability (perhaps a safe
recovery kernel), or with fewer nodes online, then it is advis-
able to omit the mpol option from automatic mount options. It
can be added later, when the tmpfs is already mounted on Mount-
Point, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.
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.
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 charac-
ter, 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 or disabled with utf8=0, utf8=no or utf8=false.
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. This
mode is the default.
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
allocsize=size
Sets the buffered I/O end-of-file preallocation size when doing
delayed allocation writeout (default size is 64KiB). Valid val-
ues for this option are page size (typically 4KiB) through to
1GiB, inclusive, in power-of-2 increments.
attr2 / noattr2
The options enable/disable (default is disabled for backward
compatibility on-disk) an "opportunistic" improvement to be made
in the way inline extended attributes are stored on-disk. When
the new form is used for the first time (by setting or removing
extended attributes) the on-disk superblock feature bit field
will be updated to reflect this format being in use.
barrier
Enables the use of block layer write barriers for writes into
the journal and unwritten extent conversion. This allows for
drive level write caching to be enabled, for devices that sup-
port write barriers.
dmapi Enable the DMAPI (Data Management API) event callouts. Use with
the mtpt option.
grpid / bsdgroups and nogrpid / 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.
ihashsize=value
Indicates that XFS is allowed to create inodes at any location
in the filesystem, including those which will result in inode
numbers occupying more than 32 bits of significance. This is
provided for backwards compatibility, but causes problems for
backup applications that cannot handle large inode numbers.
largeio / nolargeio
If nolargeio is specified, the optimal I/O reported in st_blk-
size by stat(2) will be as small as possible to allow user
applications to avoid inefficient read/modify/write I/O. If
largeio is specified, a filesystem that has a swidth specified
will return the swidth value (in bytes) in st_blksize. If the
filesystem does not have a swidth specified but does specify an
allocsize then allocsize (in bytes) will be returned instead.
If neither of these two options are specified, then filesystem
will behave as if nolargeio was specified.
logbufs=value
Set the number of in-memory log buffers. Valid numbers range
from 2-8 inclusive. The default value is 8 buffers for filesys-
tems with a blocksize of 64KiB, 4 buffers for filesystems with a
blocksize of 32KiB, 3 buffers for filesystems with a blocksize
of 16KiB 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. Size may be speci-
fied in bytes, or in kilobytes with a "k" suffix. Valid sizes
for version 1 and version 2 logs are 16384 (16k) and 32768
(32k). Valid sizes for version 2 logs also include 65536 (64k),
131072 (128k) and 262144 (256k). The default value for machines
with more than 32MiB of memory is 32768, machines with less mem-
ory 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 sec-
tion or contained within it. Refer to xfs(5).
mtpt=mountpoint
Use with the dmapi option. The value specified here will be
included in the DMAPI mount event, and should be the path of the
actual mountpoint that is used.
noalign
Data allocations will not be aligned at stripe unit boundaries.
noatime
Access timestamps are not updated when a file is read.
Make O_SYNC writes implement true O_SYNC. WITHOUT this option,
Linux XFS behaves as if an osyncisdsync option is used, which
will 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 not in effect, timestamp updates from O_SYNC
writes can be lost if the system crashes. If timestamp updates
are critical, use the osyncisosync option.
uquota / usrquota / uqnoenforce / quota
User disk quota accounting enabled, and limits (optionally)
enforced. Refer to xfs_quota(8) for further details.
gquota / grpquota / gqnoenforce
Group disk quota accounting enabled and limits (optionally)
enforced. Refer to xfs_quota(8) for further details.
pquota / prjquota / pqnoenforce
Project disk quota accounting enabled and limits (optionally)
enforced. Refer to xfs_quota(8) for further details.
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 speci-
fied, and must be a multiple of the sunit value.
swalloc
Data allocations will be rounded up to stripe width boundaries
when the current end of file is being extended and the file size
is larger than the stripe width size.
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.
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
8 user interrupt
16 problems writing or locking /etc/mtab
32 mount failure
64 some mount succeeded
NOTES
The syntax of external mount helpers is:
/sbin/mount.<suffix> spec dir [-sfnv] [-o options]
where the <suffix> is filesystem type and -sfnvo options have same
meaning like standard mount options.
FILES
/etc/fstab file system table
/etc/mtab table of mounted file systems
/etc/mtab~ lock file
/etc/mtab.tmp temporary file
/etc/filesystems a list of filesystem types to try
SEE ALSO
mount(2), umount(2), fstab(5), umount(8), swapon(8), nfs(5), xfs(5),
e2label(8), xfs_admin(8), mountd(8), nfsd(8), mke2fs(8), tune2fs(8),
losetup(8)
BUGS
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,
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.
HISTORY
A mount command existed in Version 5 AT&T UNIX.
AVAILABILITY
The mount command is part of the util-linux-ng package and is available
from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
Linux 2.6 2004-12-16 MOUNT(8)
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