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mount - mount a filesystem
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mount - mount a filesystem
mount [-lhV]
mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
mount [-fnrsvw] [-o option[,option]...]
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 /.
serves to attach the filesystem
found on some device to the big file tree.
Conversely,
command will detach it again.
The standard form of the mount command, is
mount -t type device dir
the kernel to attach the filesystem found on device (which
is of type type) at the directory dir.
The previous contents (if
invisible,
and as long as this
filesystem remains mounted, the pathname dir refers to the root of
filesystem on device.
The listing and help.
Three forms of invocation do not actually mount anything:
prints a help message
prints a version string
mount [-l] [-t type]
lists all mounted filesystems (of type type).
The option
-l adds the labels in this listing.
See below.
The bind mounts.
Since Linux 2.4.0 it is possible to remount
hierarchy somewhere else. The call is
mount --bind olddir newdir
or shortoption
mount -B olddir newdir
or fstab entry is:
/olddir /newdir none bind
call the same contents is accessible in two places.
One can also remount a single file (on a single file).
This call attaches only
filesystem,
submounts.
submounts is attached a second place using
mount --rbind olddir newdir
or shortoption
mount -R olddir newdir
Note that the filesystem mount options will remain the
point, and cannot be changed by
passing the -o option along with --bind/--rbind.
The move operation.
Since Linux 2.5.1 it is possible to atomically
tree to another place. The call is
mount --move olddir newdir
or shortoption
mount -M olddir newdir
The shared subtrees operations.
mark a mount and its
submounts as shared, private,
unbindable.
mount provides ability to create mirrors of that mount such that
mounts and umounts within any of the mirrors
propagation
master, but any not vice-versa.
propagation
abilities.
unbindable mount is a private mount
which cannot cloned through a bind operation. Detailed semantics
documented
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.
indicated by a file name (of a block special
device), like /dev/sda1, but there are other possibilities.
NFS mount, device may look like
knuth.cwi.nl:/dir.
It is possible to indicate a
device using its volume LABEL or UUID (see the -L and -U options
The proc filesystem 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
is less fortunate: the error message `none busy' from umount can
be confusing.)
(see (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 filesystems mentioned
in fstab (of the proper type and/or having
mounted as indicated, except for those
whose line contains the noauto keyword.
filesystems are mounted
simultaneously.
When mounting a
filesystem
suffices to give only the device, or only the mount point.
a list of currently
mounted filesystems in the file .
If no arguments
given to mount, this list is printed.
filesystem is mounted (say at ), the files
has somewhat more information, such as the mount options
used, but is not
necessarily
up-to-date
is possible to replace
by a symbolic link
to , 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
filesystems.
when fstab contains the user option on a line, anybody can mount
the corresponding system.
Thus, given a line
/dev/cdrom
ro,user,noauto,unhide
any user can mount the iso9660 filesystem
using the command
mount /dev/cdrom
Only the user that mounted a
filesystem can unmount it again.
If any user should be able
then use users instead of user in the fstab line.
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
if a login script makes the console user
The group option is similar, with the
restriction that the user must be member of
special file.
COMMAND LINE OPTIONS
an invocation of mount is
determined by first extracting the mount
filesystem
then applying any options specified by the -o
argument, and finally applying a -r or -w option, when present.
Command line options available for the mount command:
Output version.
Print a help message.
Verbose mode.
-p passwdfd
If the mount requires a passphrase to be entered, read
descriptor passwdfd instead of from the terminal. If mount
uses encrypted loop device and gpgkey= mount option is not being
used (no gpg key file), then mount attempts to read 65 keys from
passwdfd, each key at
characters
successfully reads 64 or 65 keys, then loop
device is put to multi-key mode. If mount encounters end-of-file
64 keys are read, then only first key is used in single-
Mount all filesystems (of the given types) mentioned in fstab.
(Used in conjunction with -a.)
Fork off a
incarnation
This will do the mounts on different
devices or different NFS servers
advanta also NFS timeouts go in parallel. A
disadvantage is that the mounts are
you cannot use this option if you want to mount both
and /usr/spool.
Causes everything to be done except for the
this ``fakes'' mounting the filesystem.
This option is
conjunction
determine what the mount command is trying to do. It can also be
used to add entries for devices that were mounted
checks for existing record in
and fails when the record already exists (with regular
non-fake mount, this check is done by kernel).
/sbin/mount.&filesystem&
Add the labels in the mount output. Mount must
permission
disk device (e.g. be suid root) for this to work.
One can set such a label
reiserfs using (8).
Mount without writing
example when
is on a read-only filesystem.
--no-canonicalize
canonicalize
The mount command canonicalizes all
paths (from command line
canonicalized
file. This option can be used together
with the -f flag for already canonicalized absolute paths.
Tolerate sloppy mount options rather
ignore mount options not supported by a filesystem type. Not all
filesystems support this option. This option exists for
of the Linux autofs-based automounter.
Mount the filesystem read-only. A synonym is -o ro.
on the filesystem type, state and kernel
behavior, the system may still write to the device. For example,
Ext3 or ext4 will replay its journal if the filesystem is dirty.
To prevent this kind of write access, you may want to mount ext3
filesystem
"ro,noload" mount options or set the
block device to read-only mode, see command (8).
Mount the filesystem read/write. This is the default. A
Mount the partition that has the specified label.
the specified uuid.
options require the file
2.1.116) to exist.
-t vfstype
The argument following the -t is used to indicate the filesystem
filesystem
coherent, cramfs,
debugfs, devpts, efs, ext, ext2, ext3, ext4, hfs, hfsplus, hpfs,
jfs, minix, msdos, ncpfs, nfs, nfs4, ntfs, proc, qnx4,
ramfs, reiserfs, romfs, smbfs, sysv, tmpfs,
xfs, xiafs.
Note that coherent, sysv and
xenix are equivalent and that xenix and coherent will be removed
the future — use sysv instead. Since kernel
version 2.1.21 the types ext and xiafs
known as usbdevfs.
Note, the real list of
all supported filesystems depends on your kernel.
For most types all the mount program has to do is issue a simple
filesystem type is required.
For a few types however (like nfs,
ad hoc code is necessary. The nfs,
nfs4, cifs, smbfs, and ncpfs filesystems have a
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
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
specified,
will try to guess the desired type.
Mount uses the blkid
or volume_id library for guessing
does not turn up anything that looks familiar, mount will try to
read the file /etc/filesystems, or,
filesystem types listed there
will be tried, except for those that are labeled "nodev"
proc and nfs).
If /etc/filesystems ends in a line with
a single * only, mount will read
afterwards.
The auto type may be useful for user-mounted floppies.
file /etc/filesystems can be useful to change the probe order
(e.g., to try vfat before msdos or ext3 before ext2) or
autoloader.
Warning: the probing uses a
heuristic (the
appropriate
the wrong filesystem type, possibly with catastrophic
consequences. If your data
one type may be specified in a comma separated list.
The list of filesystem types can be prefixed with no to
filesystem types on which no action should be taken.
can be meaningful with the -a option.)
For example, the command:
mount -a -t nomsdos,ext
mounts all filesystems except those of type msdos and ext.
Used in conjunction with -a, to limit the set of filesystems
the -a is applied.
Like -t in this regard except that it
is useless except in
mount -a -O no_netdev
filesystems
the option
_netdev specified in the options field in the
It is different from -t in that each option
leading no at the beginning of one option does not negate the
The -t and -O options are c
mount -a -t ext2 -O _netdev
filesystems
with the _netdev option, not all
filesystems that are either ext2
specified.
by a comma
separated string of options. For example:
mount LABEL=mydisk -o noatime,nouser
For more details, see FILESYSTEM INDEPENDENT MOUNT
FILESYSTEM SPECIFIC MOUNT OPTIONS sections.
-B, --bind
that its contents are
available in both places). See above.
-R, --rbind
Remount a subtree and all possible submounts somewhere else
that its contents are available in both places). See above.
-M, --move
Move a subtree to some other place. See above.
FILESYSTEM INDEPENDENT MOUNT OPTIONS
Some of these options could be enabled or disabled by
options in
/proc/mounts.
The following options apply to any filesystem
not every filesystem actually honors them - e.g., the sync option
today has effect only for ext2, ext3, fat, vfat and ufs):
All I/O to the filesystem should be
asynchronously.
also the sync option.)
strictatime mount option.
Do not update inode access times on this
filesystem
faster access on the news spool to speed up news servers).
Can be mounted with the -a option.
noauto Can
explicitly (i.e., the -a option will not
cause the filesystem to be mounted).
context=context,
fscontext=context,
defcontext=context
rootcontext=context
context= option is useful when mounting filesystems that do
not support extended attributes, such as a floppy or
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
compatibility
xattr-supporting filesystems on earlier 2.4.&x& kernel versions.
Even where xattrs are supported, you can save time not having to
entire disk one security
context=system_u:object_r:removable_t.
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
support. The fscontext option sets the overarching
filesystem label to a specific security context. This filesystem
from the individual labels on the files. It
represents the entire filesystem for certain kinds of permission
such as during mount or file creation.
Individual file
themselves.
the aggregate
context that fscontext provides, in addition
same label for individual files.
default security context for unlabeled files
using defcontext= option.
policy and requires a filesystem that
supports xattr labeling.
The rootcontext= option allows you to explicitly label the
mounted before that FS or inode because
visable to userspace. This was found to
like stateless linux.
For more details, see (8)
dev, exec, auto, nouser, and
Interpret character or block special devices on the filesystem.
Do not interpret character or block special devices on the
directory inode access times on this filesystem. This is
the default.
nodiratime
Do not update directory inode access times on this filesystem.
All directory updates
filesystem
synchronously.
This affects the following system calls: creat,
link, unlink, symlink, mkdir, rmdir, mknod and rename.
Permit execution of binaries.
noexec Do not allow direct execution of any
filesystem.
was possible to run binaries
anyway using a command like /lib/ld*.so /mnt/binary. This
fails since Linux 2.4.25 / 2.6.0.)
an ordinary (i.e., non-root) user to mount the filesystem
if one of his groups matches the
the options nosuid and nodev (unless overridden
by subsequent options, as in the option line group,dev,suid).
Every time the inode is modified, the i_version
incremented.
noiversion
Do not increment the i_version inode field.
Allow mandatory locks on this filesystem. See (2).
nomand Do not allow mandatory locks on this filesystem.
filesystem resides on a device that requires network access
(used to prevent the
attempting
filesystems until the network has been enabled on the system).
nofail Do not report errors for this device if it does not exist.
relative to modify or change time.
Access time is only updated if
or change time. (Similar to
noatime, but doesn't break mutt or other applications that
been read since the last time it was
modified.)
norelatime
Do not use relatime feature.
strictatime
strictatime
explicitly requesting full atime updates. This makes
it possible for kernel to defaults to relatime
still allow userspace to override it. For more details about the
default system mount options see /proc/mounts.
nostrictatime
set-user-identifier
or set-group-identifier bits to take
nosuid Do not allow set-user-identifier or set-group-identifier bits to
(This seems safe, but is in fact rather unsafe if
you have (1) installed.)
Allow an ordinary (i.e., non-root) user to mount the
filesystem
the device.
This option implies the
overridden
subsequent
options, as in the option line owner,dev,suid).
already-mounted
filesystem.
commonly used to
filesystem,
especially
to make a readonly filesystem writeable. It does not
change device or mount point.
The remount functionality follows the standard way how the mount
means the mount
command doesn't read fstab (or mtab) only when a device and
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=
internally generated and maintained by the mount command.
mount -o remount,rw
reads fstab (or mtab) and merges these
options with options from command line ( -o ).
Mount the filesystem read-only.
Mount the filesystem read-write.
All I/O to the filesystem should be done synchronously. In
limited number of write cycles (e.g. some flash
drives) "sync" may cause life-cycle shortening.
Allow an ordinary user to mount the filesystem.
The name of the
mtab so that he can unmount the
filesystem again.
nodev (unless overridden by subsequent options, as
in the option line user,exec,dev,suid).
nouser Forbid
filesystem.
This is the default.
and unmount the filesystem.
option implies the options noexec,
overridden
subsequent
users,exec,dev,suid).
FILESYSTEM SPECIFIC MOUNT OPTIONS
The following options apply only to certain filesystems.
by filesystem. They all follow the -o flag.
are supported depends a bit on the running kernel.
subdirectory
Documentation/filesystems.
Mount options for adfs
uid=value and gid=value
Set the owner and group of the files in the filesystem (default:
uid=gid=0).
ownmask=value and othmask=value
Set the permission mask for ADFS 'owner' permissions and 'other'
permissions,
respectively
respectively).
/usr/src/linux/Documentation/filesystems/adfs.txt.
Mount options for affs
uid=value and gid=value
the owner and group of the root of the filesystem (default:
uid=gid=0, but with option uid or gid without
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
to value & 0777 disregarding the
original permissions.
Add search permission to directories that
have read permission.
The value is given in octal.
protection
filesystem.
Set uid and gid of the root of the filesystem to the uid and gid
of the mount point upon the first sync or umount, and then clear
this option. Strange...
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
symbolic link.
reserved=value
the start of the
root=value
Give explicitly the location of the root block.
Give blocksize. Allowed values are 512, , 4096.
grpquota|noquota|quota|usrquota
utilities may react to such strings in .)
Mount options for cifs
(8) man page (cifs-mount
package must be installed).
Mount options for coherent
Mount options for debugfs
The debugfs filesystem is a pseudo filesystem, traditionally mounted on
There are no mount options.
Mount options for devpts
devpts filesystem is a pseudo filesystem, traditionally mounted on
In order to acquire
/dev/ptmx;
the number of the pseudo terminal is then made available to
uid=value and gid=value
owner or the group of newly created PTYs to the
specified values. When nothing is specified, they will be set to
UID and GID of the creating process.
For example, if there
is a tty group with GID 5, then gid=5 will cause
PTYs to belong to the tty group.
mode=value
the mode of newly created PTYs to the specified value.
default is 0600.
A value of mode=620 and gid=5 makes
the default on newly created PTYs.
newinstance
filesystem,
indices of ptys allocated in this new instance
independent
of indices created in other instances of devpts.
of devpts without this newinstance option share the
same set of pty indices (i.e legacy mode).
Each mount of devpts
with the newinstance option has a private set of pty indices.
mainly used to support containers in the linux
kernel. It is implemented in linux kernel versions starting with
CONFIG_DEVPTS_MULTIPLE_INSTANCES
configuration.
effectively, /dev/ptmx must be a symbolic
link to pts/ptmx.
Documentation/filesystems/devpts.txt
the linux kernel source tree for details.
ptmxmode=value
in the devpts
filesystem.
newinstance option above), each instance has a private ptmx node
in the root of the devpts filesystem (typically /dev/pts/ptmx).
For compatibility with older versions of the kernel, the default
the new ptmx node is 0000.
ptmxmode=value specifies a
more useful mode for the ptmx node
recommended
when the newinstance option is specified.
implemented
starting with 2.6.29. Further
CONFIG_DEVPTS_MULTIPLE_INSTANCES
configuration.
Mount options for ext
Note that the `ext' filesystem is obsolete. Don't use it.
Linux version 2.1.21 extfs is no longer part of the kernel source.
Mount options for ext2
filesystem
is the standard Linux filesystem.
Since Linux
2.5.46, for most
determined
filesystem superblock. Set them with (8).
Support POSIX Access Control Lists (or not).
bsddf|minixdf
call. The minixdf
behaviour is to return in the f_blocks field the total number of
filesystem, while the bsddf behaviour (which is
the default) is to subtract the overhead blocks used by the ext2
filesystem and not available for file storage. Thus
% mount /k - df /k; umount /k
Filesystem
1024-blocks
Used Available Capacity Mounted on
% mount /k - df /k; umount /k
Filesystem
1024-blocks
Used Available Capacity Mounted on
that one can add command line
options to the options given in .)
check={none|nocheck}
No checking is done at mount time. This is the default. This
is wise to invoke (8) every now and then, e.g.
at boot time.
Print debugging info upon each (re)mount.
errors={continue|remount-ro|panic}
Define the behaviour when
encountered.
filesystem
continue, or remount the filesystem read-only, or panic and halt
The default is set in the filesystem superblock,
and can be changed using (8).
grpid|bsdgroups and nogrpid|sysvgroups
These options define what group id a newly
it takes the group id of the directory in
otherwise (the default) it takes the
the current process, unless the directory has the setgid bit
set, in which case it takes the gid from the
directory,
and also gets the setgid bit set if it is a directory itself.
grpquota|noquota|quota|usrquota
These options are accepted but ignored.
Do not attach buffer_heads to file pagecache. (Since 2.5.49.)
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
resgid=n and resuid=n
filesystem
percentage
available space (by default 5%, see (8)
(Roughly: whoever has the
specified group.)
use block n as superblock. This could be
useful when the filesystem has been damaged.
superblock would be made every 8192 blocks: in block 1,
, ... (and one got
filesystem).
superblock) option to reduce the number of
superblocks,
version 1.15 this is the default. Note that this may
mean that ext2 filesystems created by a recent mke2fs cannot
under Linux 2.0.*.)
The block number here uses 1k
units. Thus, if you
filesystem with 4k blocks, use "sb=131072".
user_xattr|nouser_xattr
Support "user." extended attributes (or not).
Mount options for ext3
ext3 filesystem is a version of the ext2 filesystem which has been
enhanced with journalling.
It supports the same
well as the following additions:
journal=update
Update the ext3 filesystem's journal to the current format.
journal=inum
Otherwise, it specifies the
the ext3 filesystem'
ext3 will create
a new journal, overwriting the old contents of
inode number is inum.
noload Do not load the ext3 filesystem's journal on mounting.
data={journal|ordered|writeback}
journalling
Metadata is
always journaled.
To use modes other than ordered on
filesystem,
pass the mode to the kernel as boot parameter, e.g.
rootflags=data=journal.
All data is committed into the
written into the main filesystem.
default mode.
All data is forced directly
out to the main file system prior to its
committed to the journal.
Data ordering is not preserved - data may be written into
the main filesystem after its metadata has been committed
rumoured to be the highest-
throughput option.
guarantees
filesystem
integrity,
allow old data to appear in
files after a crash and journal recovery.
barrier=0 / barrier=1
enables/disables
barrier=1 enables it.
The ext3 filesystem does not enable write
barriers by default.
commit=nrsec
Sync all data and metadata
value is 5 seconds. Zero means default.
user_xattr
Enable Extended User Attributes. See the (5) manual page.
Enable POSIX Access Control Lists. See the (5) manual page.
Mount options for ext4
filesystem
an advanced level of the ext3 filesystem
incorporates
scalability
reliability
enhancements
supporting large filesystem.
journal_dev,
[no]user_xattr [no]acl, bsddf, minixdf, debug, errors, data_err, grpid,
bsdgroups,
sysvgroups,
sb, quota, noquota,
grpquota, usrquota and [no]bh are backwardly compatible
journal_checksum
checksumming
transactions.
allow the recovery code in
corruption in the kernel.
It is a compatible change and will be
ignored by older kernels.
journal_async_commit
descriptor
older kernels cannot mount the
device. This will enable
journal=update
Update the ext4 filesystem's journal to the current format.
barrier=0 / barrier=1 / barrier / nobarrier
This enables/disables the use of write barriers in the jbd code.
barrier=0 disables, barrier=1 enables.
This also requires an IO
stack which can support barriers, and if jbd gets an error on
again with a warning.
barriers enforce proper on-disk
performance penalty.
If your disks are
battery-backed
performance.
The mount options "barrier"
"nobarrier"
also be used to enable or disable barriers, for consistency with
other ext4 mount options.
The ext4 filesystem enables write barriers by default.
inode_readahead=n
This tuning parameter controls the maximum number of inode table
blocks that ext4's inode table readahead algorithm will pre-read
into the buffer cache.
The default value is 32 blocks.
Number of filesystem blocks that mballoc will
allocation
and alignment. For RAID5/6 systems this should
be the number of data disks *
filesystem
Deferring block allocation until write-out time.
nodelalloc
allocation. Blocks are allocation when data is
copied from user to page cache.
max_batch_time=usec
additional
filesystem
operations
be batch together with a synchronous
write operation. Since a synchronous write operation is going to
a commit and then a wait for the I/O complete, it doesn't
cost much, and can be a huge throughput win, we wait for a small
amount of time to see if any other transactions can piggyback on
synchronous
automatically
for the speed of the disk, by measuring the
amount of time (on average) that it takes to finish committing a
transaction. Call this time the "commit time".
If the time that
the transactoin has been running is less than the
commit time to see if other
operations will join the transaction. The commit time is
max_batch_time,
which defaults to 15000us (15ms). This
optimization
max_batch_time to 0.
min_batch_time=usec
sets the commit time (as described above) to be
min_batch_time.
microseconds.
Increasing
parameter may improve the throughput of multi-
threaded, synchronous workloads on very fast disks, at the
of increasing latency.
journal_ioprio=prio
priority (from 0 to 7, where 0 is the highest priorty)
which should be used for I/O operations submitted by
kjournald2
operation.
to 3, which is a
slightly higher priority than the default I/O priority.
auto_da_alloc|noauto_da_alloc
Many broken applications don't use fsync() when
noauto_da_alloc
replacing existing files via patterns such as
open("foo.new")/write(fd,..)/close(fd)/ rename("foo.new",
or worse yet
fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
If auto_da_alloc is enabled, ext4 will detect
replace-via-
replace-via-truncate
force that any
delayed allocation blocks are allocated such that
data=ordered
mode, the data
blocks of the new file are forced to disk
is commited.
This provides roughly the same level of
guarantees as ext3, and avoids the
"zero-length"
when a system crashes before the delayed allocation
blocks are forced to disk.
Mount options for fat
(Note: fat is not a separate filesystem,
msdos, umsdos and vfat filesystems.)
blocksize={512|1024|2048}
Set blocksize (default 512). This option is obsolete.
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
permissions
The default is the umask of the current process.
value is given in octal.
dmask=value
Set the umask applied to directories only.
The default
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.
If current process is in group of file's
can change timestamp.
Other users can change timestamp.
from `dmask' option. (If the directory is
writable, (2) is also allowed. I.e. ~dmask & 022)
Normally (2) checks current process is owner of
CAP_FOWNER
capability.
But FAT filesystem doesn't
have uid/gid on disk, so normal check is
unflexible.
this option you can relax it.
check=value
Three different levels of pickyness can be chosen:
case are accepted and equivalent, long
verylongname.foobar
verylong.foo),
and embedded spaces are
accepted in each name part (name and extension).
Like "relaxed", but many special
characters
spaces, etc.) are rejected.
This is the default.
but names may not contain long parts and
special characters that are sometimes used on Linux,
accepted by MS-DOS are rejected. (+, =, spaces,
codepage=value
Sets the codepage for converting to shortname characters on
and VFAT filesystems. By default, codepage 437 is used.
conv={b[inary]|t[ext]|a[uto]}
The fat filesystem can perform CRLF&--&NL (MS-DOS text format to
conversion
conversion modes are available:
binary no translation is performed.
This is the default.
CRLF&--&NL translation is performed on all files.
CRLF&--&NL
translation
on all files that
don't have a "well-known binary" extension. The
extensions
fs/fat/misc.c (as of 2.0, the list
ovl, ovr, obj, lib, dll, pif, arc, zip,
lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz,
bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl,
Programs that do
conversion.
people have had their data ruined by this
translation. Beware!
For filesystems
conversion
(fromdos/todos) is available. This option is obsolete.
cvf_format=module
Forces the driver to use the CVF (Compressed Volume File) module
cvf_module instead of auto-detection.
cvf_format=xxx
controls on-demand CVF
module loading.
This option is obsolete.
cvf_option=option
Option passed to the CVF module. This option is obsolete.
Turn on the
filesystem
parameters
data are also
printed if the parameters appear to be inconsistent).
fat={12|16|32}
Specify a 12, 16 or 32 bit fat.
FAT type detection routine.
Use with caution!
iocharset=value
Character set to use for converting between 8 bit characters and
16 bit Unicode
characters.
iso8859-1.
filenames are stored on disk in Unicode format.
tz=UTC This
option disables the conversion of timestamps between local
time (as used by Windows on
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.
Turn on the quiet flag.
Attempts to chown or chmod files do not
return errors, although they fail. Use with caution!
If set, the execute permission bits of the file will be
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
Not set by default.
If set, the filesystem will try to flush to disk more early than
Not set by default.
Use the "free clusters" value stored on FSINFO. It'll be used to
clusters without scanning disk. But
it's not used by default, because recent Windows don't update it
some case. If you are sure the "free clusters" on
FSINFO is correct, by this option you can avoid scanning disk.
dots, nodots, dotsOK=[yes|no]
Various misguided attempts to force Unix or DOS conventions onto
a FAT filesystem.
Mount options for hfs
creator=cccc, type=cccc
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
used for all directories, all regular files, or
all files and directories.
Defaults to the umask of the current
Defaults to leaving that
decision to the
anything but a CDROM as underlying device.
part=n Select partition number n from the device.
Only makes sense for
Defaults to not parsing the partition table at all.
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
of the current process.)
umask=value
the permissions that are not
present). The default is the umask of the current process.
value is given in octal.
case={lower|asis}
Convert all files names to lower case, or leave them.
case=lower.)
conv={binary|text|auto}
For conv=text,
particular,
followed by NL) when reading a file.
For conv=auto, choose more
conv=binary
conv=text.
conv=binary, just read what is in the file. This is the default.
Do not abort mounting when certain consistency checks fail.
Mount options for iso9660
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
udf filesystem.)
(i.e., DOS-like
restrictions on filename length), and in addition all characters are in
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
like features.
Basically there are extensions to each directory record
that supply all of the additional information, and when Rock
filesystem
indistinguishable
filesystem (except that it is read-only, of course).
norock Disable the use of Rock Ridge extensions, even if available. Cf.
extensions,
available. Cf. map.
check={r[elaxed]|s[trict]}
With check=relaxed, a filename is first converted to lower
probably only meaningful
together with norock and map=normal.
(Default: check=strict.)
uid=value and gid=value
Give all files in the filesystem the indicated user or group id,
overriding
information
in the Rock Ridge
extensions.
(Default: uid=0,gid=0.)
map={n[ormal]|o[ff]|a[corn]}
For non-Rock Ridge volumes, normal name translation
lower case ASCII, drops a trailing `;1', and converts `;' to
With map=off no name
translation
map=normal.)
is like map=normal but also
apply Acorn extensions if present.
mode=value
For non-Rock Ridge volumes, give all files the
permission
for everybody.)
Since Linux 2.1.37
one no longer needs to specify the mode in
indicated by a leading 0.)
unhide Also
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}
block=1024.)
conv={a[uto]|b[inary]|m[text]|t[ext]}
(Default: conv=binary.)
Since Linux 1.3.54 this option
non-binary
dangerous, possibly leading to silent data corruption.)
If the high byte of the file length contains other garbage,
the high order bits of the file
This implies that a file cannot be larger than 16MB.
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
Microsoft's
extensions.
iocharset=value
Character set to use for converting 16 bit Unicode characters on
CD to 8 bit characters. The default is iso8859-1.
Convert 16 bit Unicode characters on CD to UTF-8.
Mount options for jfs
iocharset=name
set to use for converting from Unicode to ASCII.
default is to do no conversion.
iocharset=utf8
translations.
CONFIG_NLS_UTF8 to be set in the
kernel .config file.
resize=value
Resize the volume to value blocks. JFS only supports
This option is only valid during a
remount, when the
read-write.
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
performance when restoring a volume from
backup media. The integrity of the volume is not
guaranteed
the system abnormally abends.
the journal.
option to remount a volume
nointegrity
previously specified in order to restore normal behavior.
errors={continue|remount-ro|panic}
error is encountered.
filesystem
continue, or remount the filesystem read-only, or panic and halt
the system.)
noquota|quota|usrquota|grpquota
These options are accepted but ignored.
Mount options for minix
Mount options for msdos
filesystem
inconsistency,
it reports an error and sets the file system read-only.
The filesystem can be made writeable again by remounting it.
Mount options for ncpfs
Just like nfs, the ncpfs implementation expects a
ncp_mount_data)
call. This argument is
constructed by (8) and the current version of mount (2.12) does
not know anything about ncpfs.
Mount options for nfs and nfs4
the options section of the (5) man page (nfs-utils package must
be installed).
The nfs and nfs4 implementation expects a
nfs_mount_data)
to the mount system call. This argument is constructed
by (8) and the current version of mount (2.13) does
anything about nfs and nfs4.
Mount options for ntfs
iocharset=name
use when returning file names.
Unlike VFAT,
NTFS suppresses names
unconvertible
characters.
Deprecated.
New name for the option earlier called iocharset.
Use UTF-8 for converting file names.
uni_xlate={0|1|2}
`false'), do not use escape sequences for
unknown Unicode characters.
For 1 (or `yes' or
use vfat-style 4-byte escape sequences starting with ":". Here 2
give a little-endian encoding
byteswapped
posix=[0|1]
If enabled (posix=1), the filesystem distinguishes between upper
and lower case. The 8.3 alias names are presented as hard
instead of being suppressed. This option is obsolete.
uid=value, gid=value and umask=value
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
Mount options for ramfs
Ramfs is a memory based filesystem. Mount it and you have
and it is gone. Present since Linux 2.3.99pre4.
There are no mount
Mount options for reiserfs
Reiserfs is a journaling filesystem.
Instructs version 3.6 reiserfs software to mount a
filesystem, using the 3.6 format for newly created objects. This
filesystem will no longer be compatible with reiserfs 3.5 tools.
hash={rupasov|tea|r5|detect}
Choose which hash function
within directories.
Yu. Rupasov.
It is fast and
preserves locality, mapping lexicographically close
hash values.
This option should not be
used, as it causes a high probability of hash collisions.
Davis-Meyer
implemented
Fitzhardinge.
uses hash permuting bits in the name.
It gets high randomness and, therefore,
probability
of hash collisions at some CPU cost.
This may be used if
EHASHCOLLISION errors are experienced with the r5 hash.
A modified version of the rupasov hash.
and is the best choice unless the filesystem has
huge directories and unusual file-name patterns.
detect Instructs mount to detect which hash function is
examining the filesystem being mounted,
and to write
this information into the reiserfs
superblock.
filesystem.
hashed_relocation
allocator.
performance
improvements in some situations.
no_unhashed_relocation
allocator.
performance
improvements in some situations.
Disable the border allocator
performance
improvements in some
situations.
journalling.
performance
improvements in some situations at the cost of losing reiserfs's
fast recovery from crashes.
Even with this
journalling operations, save for
actual writes into
journalling
Implementation
nolog is a work in progress.
directly into its tree. This confuses
option is used to disable packing of files into
replayonly
Replay the transactions which are in the
actually mount the filesystem. Mainly used by reiserfsck.
resize=number
online expansion of reiserfs
partitions.
Instructs reiserfs to assume that
is designed for use with devices
which are under logical volume management
user_xattr
Enable Extended User Attributes. See the (5) manual page.
Enable POSIX Access Control Lists. See the (5) manual page.
Mount options for romfs
Mount options for smbfs
Just like nfs, the smbfs implementation expects a
smb_mount_data)
call. This argument is
constructed by (8) and the current version of mount (2.12) does
not know anything about smbfs.
Mount options for sysv
Mount options for tmpfs
size=nbytes
size of the filesystem.
The size is
given in bytes, and rounded up to entire pages.
The default
the memory. The size parameter also accepts a suffix %
to limit this tmpfs instance to that percentage of your physical
the default, when neither size nor nr_blocks is specified,
is size=50%
nr_blocks=
The same as size, but in blocks of PAGE_CACHE_SIZE
nr_inodes=
The maximum number of inodes for this instance. The
of the number of your physical RAM pages, or (on a machine
with highmem) the number of lowmem RAM pages, whichever
options for sizing ( size, nr_blocks, and nr_inodes)
accept a suffix k, m or g for Ki, Mi, Gi (binary kilo, mega
and can be changed on remount.
Set initial permissions of the root directory.
The user id.
The group id.
mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
allocation
policy for all files in that
instance (if the kernel CONFIG_NUMA is enabled) - which
adjusted on the fly via 'mount -o remount ...'
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
example, mpol=bind:0-3,5,7,9-15
Note that trying to mount a tmpfs with an mpol option will
kernel does not support NUMA; and will fail if
its nodelist specifies a node which
system relies on that tmpfs being mounted, but from time to time
runs a kernel built without
capability
advisable to omit the mpol option from automatic mount
when the tmpfs is already mounted on
MountPoint,
remount,mpol=Policy:NodeList
MountPoint'.
Mount options for udf
"Universal Disk Format" filesystem defined by the Optical
Storage Technology Association, and is often
also iso9660.
Set the default group.
umask= Set the default umask.
The value is given in octal.
Set the default user.
unhide Show otherwise hidden files.
Show deleted files in lists.
Unset strict conformance.
Set the NLS character set.
Set the block size. (May not work unless 2048.)
Skip volume sequence recognition.
Set the CDROM session counting from 0. Default: last session.
Override standard anchor location. Default: 256.
Override the VolumeDesc location. (unused)
partition=
Override the PartitionDesc location. (unused)
lastblock=
Set the last block of the filesystem.
Override the fileset block location. (unused)
Override the root directory location. (unused)
Mount options for ufs
ufstype=value
is a filesystem widely used in different operating systems.
The problem are differences among implementations.
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:
default, read only.
(Don't forget to give the -r option.)
filesystems
(NetBSD,FreeBSD,OpenBSD).
For filesystems created by SunOS or Solaris on Sparc.
sunx86 For filesystems created by Solaris on x86.
For filesystems created by HP-UX, read-only.
filesystems
NeXTStep (on NeXT station)
(currently read only).
nextstep-cd
For NextStep CDROMs (block_size == 2048), read-only.
filesystems
(currently
same filesystem type is also used by Mac OS
onerror=value
Set behaviour on error:
If an error is encountered, cause a kernel panic.
[lock|umount|repair]
These mount options don't do 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
Mount options for vfat
First of all, the mount options for fat
recognized.
option is explicitly killed by vfat.
Furthermore, there are
characters
sequences.
This lets you backup and restore filenames that
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
character, is: ':', (u & 0x3f), ((u&&6) & 0x3f), (u&&12).
Allow two files with names that only differ in case.
to make a short name without sequence number, before
trying name~num.ext.
UTF8 is the filesystem safe 8-bit encoding of
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}
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: :
the short name to low store a
long name when the short name is not all upper case. This
mode is the default.
the short name to upp store a
long name when the short name is not all upper case.
Display store a long name
short name is not all lower case or all upper case.
store a long name when the
short name is not all upper case.
Mount options for usbfs
devuid=uid and devgid=gid and devmode=mode
Set the owner and group and mode of
filesystem
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
filesystem
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
uid=gid=0, mode=0444). The mode is given in octal.
Mount options for xenix
Mount options for xfs
allocsize=size
the buffered I/O end-of-file preallocation size when doing
delayed allocation writeout
values for this option are page size (typically 4KiB) through to
1GiB, inclusive, in power-of-2 increments.
attr2|noattr2
The options enable/disable (default
compatibility on-disk) an "opportunistic" improvement to be made
in the way inline extended attributes are stored on-disk.
new form is used for the first time (by setting or removing
extended attributes) the on-disk superblock
will be updated to reflect this format being in use.
of block layer write barriers for writes into
the journal and unwritten extent conversion.
for devices that
support write barriers.
Enable the DMAPI (Data Management API) event callouts.
the mtpt option.
grpid|bsdgroups and nogrpid|sysvgroups
what group ID a newly created file gets.
When grpid is set, it takes the group ID
otherwise (the default) it takes the fsgid
of the current process, unless the directory has the setgid
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
Sets the number of hash buckets available for
inodes of the specified mount point.
If a value of zero
is used, the value selected by the
displayed in .
ikeep|noikeep
clusters are emptied of inodes, keep them around on
the disk (ikeep) - this is the traditional XFS behaviour and
Using the noikeep option, inode
clusters are returned to the free space pool.
Indicates that XFS is allowed to create inodes at
filesystem,
including those which will result in inode
numbers occupying more than 32 bits of
significance.
compatibility, but causes problems for
backup applications that cannot handle large inode numbers.
largeio|nolargeio
specified,
st_blksize by (2) will be as small as possible to allow user
applications to avoid
inefficient
read/modify/write
specified, a filesystem that has a swidth specified
will return the swidth value (in bytes) in
st_blksize.
filesystem
does not have a swidth specified but does specify an
allocsize then allocsize (in bytes) will
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.
inclusive.
filesystems with a blocksize of 64KiB, 4 buffers for filesystems
3 buffers for filesystems with a
blocksize of 16KiB and 2 buffers for all
configurations.
Increasing
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
specified in bytes, or in kilobytes with a
sizes for version 1 and version 2 logs are 16384 (16k) and 32768
Valid sizes for version 2 logs also include 65536 (64k),
8k) and 6k).
The default value for machines
with more than 32MiB of memory
memory use 16384 by default.
logdev=device and rtdev=device
an external log (metadata journal) and/or real-time device.
An XFS filesystem has up to three parts: a data section,
The real-time section is
optional, and the log section can
section or contained within it.
Refer to (5).
mtpt=mountpoint
The value specified here will be
included in the DMAPI mount event, and should be the path of the
actual mountpoint that is used.
Data allocations will not be aligned at stripe unit boundaries.
Access timestamps are not updated when a file is read.
norecovery
The filesystem will be mounted without running log recovery.
the filesystem was not cleanly unmounted, it
inconsistent
norecovery mode.
Some files or
directories may not be accessible because of this.
Filesystems
norecovery
must be mounted read-only or the mount will
nouuid Don't check for double mounted filesystems using the
filesystem
This is useful to mount LVM snapshot volumes.
osyncisosync
O_SYNC writes implement true O_SYNC.
WITHOUT this option,
Linux XFS behaves as if an osyncisdsync option
will make writes to files opened with the O_SYNC flag set behave
as if the O_DSYNC flag had been used instead.
in better performance without compromising data safety.
if this option is not in effect, timestamp updates
can be lost if the system crashes.
If timestamp updates
are critical, use the osyncisosync option.
uquota|usrquota|uqnoenforce|quota
User disk quota
accounting
(optionally)
Refer to (8) for further details.
gquota|grpquota|gqnoenforce
accounting
and limits (optionally)
enforced. Refer to (8) for further details.
pquota|prjquota|pqnoenforce
Project disk quota accounting enabled
(optionally)
enforced. Refer to (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
mount system call will
restore the value from the superblock.
For filesystems that are
these options can be used to
override the information in the
superblock
underlying
layout changes after the filesystem has been created.
specified, and must be a multiple of the sunit value.
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
2.1.21 xiafs is no longer part of the kernel source.
THE LOOP DEVICE
further possible type is a mount via the loop device. For example,
the command
mount /tmp/fdimage
-t vfat -o loop=/dev/loop3
will set up the loop
/dev/loop3
correspond
/tmp/fdimage, and then mount this device on .
namely loop, offset,
sizelimit,
encryption,
cleartextkey
itercountk
really options to (8).
(These options can be
filesystem type.)
If the mount requires a passphrase, you will be prompted for one unless
you specify a file descriptor to read from instead with the -p
line option, or specify a file name with cleartextkey mount option.
no explicit loop device is mentioned (but just an option `-o
try to find some unused loop device and use
Since Linux 2.6.25 is supported auto-destruction of
be freed by umount
independently on .
You can also free a loop device by hand, using `losetup -d' or
RETURN CODES
mount has the following return codes (the bits can be ORed):
incorrect invocation or permissions
system error (out of memory, cannot fork, no more loop devices)
internal mount bug
user interrupt
problems writing or locking
mount failure
some mount succeeded
The syntax of external mount helpers is:
/sbin/mount.&suffix& spec dir [-sfnv] [-o options]
filesystem
type and -sfnvo options have same
meaning like standard mount options.
filesystem table
table of mounted filesystems
/etc/mtab~
/etc/mtab.tmp
temporary file
/etc/filesystems
a list of filesystem types to try
(2), (2), (5), (8),
(8), (8), (8),
It is possible for a corrupted filesystem to cause a crash.
Some Linux filesystems don't support -o sync and -o dirsync (the
filesystems 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
parameters,
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
particular, it may well fail if the
kernel was compiled with devfs but devfs is not mounted.
It is possible that files
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.
particular case the mount command may reports
unreliable information about a NFS mount
file usually contains more reliable information.)
on NFS filesystem referenced by file descriptors (i.e.
the fcntl and ioctl families of functions)
inconsistent
to the lack of consistency check in kernel even if noac is
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