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MOUNT(8)		     System Administration		      MOUNT(8)

       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

       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 filesystem 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 filesystem	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
       filesystem remains mounted, the pathname	dir refers to the root of  the
       filesystem on device.

       If only directory or device is given, for example:

	      mount /dir

       then mount looks	for a mountpoint and if	not found then for a device in
       the /etc/fstab file. It's possible to use --target or --source  options
       to avoid	ambivalent interpretation of the given argument. For example

	      mount --target /mountpoint

       The listing and help.
	      The listing mode is maintained for backward compatibility	only.

	      For  more	robust and definable output use	findmnt(8), especially
	      in your scripts. Note that control characters in the  mountpoint
	      name are replaced	with '?'.

	      mount [-l] [-t type]
		     lists all mounted filesystems (of type type).  The	option
		     -l	adds the labels	in this	listing.  See below.

       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   It  is possible to indicate a block special
	      device using its filesystem LABEL	or UUID	(see the -L and	-U op-
	      tions  below)  and  partition  PARTUUID  or PARTLABEL (partition
	      identifiers are supported	for GUID Partition Table (GPT) and MAC
	      partition	tables only).

	      The recommended setup is to use tags (e.g. LABEL=<label>)	rather
	      than /dev/disk/by-{label,uuid,partuuid,partlabel}	udev  symlinks
	      in  the  /etc/fstab file.	The tags are more readable, robust and
	      portable.	The mount(8) command internally	uses udev symlinks, so
	      use  the	symlinks in /etc/fstab has no advantage	over the tags.
	      For more details see libblkid(3).

	      Note that	mount(8) uses UUIDs as strings.	The UUIDs from command
	      line  or fstab(5)	are not	converted to internal binary represen-
	      tation. The string representation	of the UUID should be based on
	      lower case characters.

	      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 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
	      default  location	 of  the  fstab(5) file	could be overridden by
	      --fstab <path> command line option (see below for	more details).

	      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 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-

	      When  mounting  a	filesystem mentioned in	fstab or mtab, it suf-
	      fices to give only the device, or	only the mount point.

	      The programs mount and  umount  maintain	a  list	 of  currently
	      mounted  filesystems in the file /etc/mtab.  If no arguments are
	      given to mount, this list	is printed.

	      The mount	program	does not read the /etc/fstab  file  if	device
	      (or  LABEL,  UUID, PARTUUID or PARTLABEL)	and dir	are specified.
	      For example:

		     mount /dev/foo /dir

	      If you want to override mount options from /etc/fstab  you  have
	      to use:

		     mount device|dir -o <options>

	      and then the mount options from command line will	be appended to
	      the list of options from /etc/fstab.   The  usual	 behaviour  is
	      that the last option wins	if there is more duplicated options.

	      When  the	 proc  filesystem is mounted (say at /proc), the files
	      /etc/mtab	and /proc/mounts have very similar contents. The  for-
	      mer  has	somewhat  more	information, such as the mount options
	      used, but	is not necessarily up-to-date (cf. the -n  option  be-
	      low).  It	is possible to replace /etc/mtab by a symbolic link to
	      /proc/mounts, and	especially when	you have very large numbers of
	      mounts  things  will  be much faster with	that symlink, but some
	      information is lost that way, and	in particular using the	"user"
	      option will fail.

       The non-superuser mounts.
	      Normally,	 only  the  superuser can mount	filesystems.  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 filesystem	found on his CDROM us-
	      ing the command

		     mount /dev/cdrom


		     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 re-
	      striction	 that the user must be member of the group of the spe-
	      cial file.

       The bind	mounts.
	      Since Linux 2.4.0	it is possible to remount part of the file hi-
	      erarchy somewhere	else. The call is
		     mount --bind olddir newdir
	      or shortoption
		     mount -B 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). It's also
	      possible	to  use	 the  bind mount to create a mountpoint	from a
	      regular directory, for example:

		     mount --bind foo foo

	      The bind mount call attaches only	(part of) a single filesystem,
	      not possible submounts. The entire file hierarchy	including sub-
	      mounts 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  same  as
	      those  on	 the  original	mount  point, and cannot be changed by
	      passing the -o option along with --bind/--rbind. The  mount  op-
	      tions can	be changed by a	separate remount command, for example:

		     mount --bind olddir newdir
		     mount -o remount,ro newdir

	      Note  that  behavior  of	the  remount  operation	depends	on the
	      /etc/mtab	file. The first	command	stores the 'bind' flag to  the
	      /etc/mtab	 file  and  the	second command reads the flag from the
	      file.  If	you have a system without the /etc/mtab	file or	if you
	      explicitly  define  source  and  target  for the remount command
	      (then mount(8) does not read /etc/mtab), then you	 have  to  use
	      bind flag	(or option) for	the remount command too. For example:

		     mount --bind olddir newdir
		     mount -o remount,ro,bind olddir newdir

	      Note  that  remount,ro,bind  will	 create	a read-only mountpoint
	      (VFS entry), but the  original  filesystem  suberblock  will  be
	      still  writable,	it means that the olddir will be writable, but
	      the newdir will be read-only.

       The move	operation.
	      Since Linux 2.5.1	it is possible to atomically  move  a  mounted
	      tree to another place. The call is
		     mount --move olddir newdir
	      or shortoption
		     mount -M olddir newdir
	      This  will  cause	 the  contents which previously	appeared under
	      olddir to	be accessed under newdir.  The	physical  location  of
	      the  files  is  not  changed.   Note that	the olddir has to be a

	      Note that	moving a mount residing	under a	shared	mount  is  in-
	      valid  and unsupported. Use findmnt -o TARGET,PROPAGATION	to see
	      the current propagation flags.

       The shared subtrees operations.
	      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 be	cloned through a bind operation. Detailed semantics is
	      documented in  Documentation/filesystems/sharedsubtree.txt  file
	      in the kernel source tree.

	      Supported	operations:
		     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

	      mount(8) does not	read fstab(5) when --make-* operation  is  re-
	      quested.	All  necessary information has to be specified on com-
	      mand line.

	      Note that	Linux kernel does not allow to change more propagation
	      flags by one mount(2) syscall and	the flags cannot be mixed with
	      another mount options.

	      Since util-linux 2.23 mount command allows to use	more  propaga-
	      tion flags together and with another mount operations. This fea-
	      ture is EXPERIMENTAL.  The propagation flags are applied by  ad-
	      ditional mount(2)	syscalls after previous	successful mount oper-
	      ation. Note that this use	case is	not  atomic.  The  propagation
	      flags  is	possible to specify in fstab(5)	as mount options (pri-
	      vate, slave, shared, unbindable, rprivate, rslave, rshared, run-

	      For example
		     mount --make-private --make-unbindable /dev/sda1 /A

	      is the same as
		     mount /dev/sda1 /A
		     mount --make-private /A
		     mount --make-unbindable /A

       The  full set of	mount options used by an invocation of mount is	deter-
       mined by	first extracting the mount options for the filesystem from the
       fstab  table,  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:

       -V, --version
	      Output version.

       -h, --help
	      Print a help message.

       -v, --verbose
	      Verbose mode.

       -a, --all
	      Mount all	filesystems (of	the given types) mentioned in fstab.

       -F, --fork
	      (Used in conjunction with	-a.)  Fork off a  new  incarnation  of
	      mount for	each device.  This will	do the mounts on different de-
	      vices or different NFS servers in	parallel.  This	has the	advan-
	      tage that	it is faster; also NFS timeouts	go in parallel.	A dis-
	      advantage	is that	the mounts are done in undefined order.	 Thus,
	      you  cannot  use	this option if you want	to mount both /usr and

       -f, --fake
	      Causes everything	to be done except for the actual system	 call;
	      if  it's	not  obvious,  this ``fakes'' mounting the filesystem.
	      This option is useful in conjunction with	the -v flag to	deter-
	      mine what	the mount command is trying to do. It can also be used
	      to add entries for devices that were mounted earlier with	the -n
	      option.  The  -f	option checks for existing record in /etc/mtab
	      and fails	when the record	already	exists (with regular  non-fake
	      mount, this check	is done	by kernel).

       -i, --internal-only
	      Don't  call  the	/sbin/mount.<filesystem> helper	even if	it ex-

       -l, --show-labels
	      Add the 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, ext3 or ext4 using the	 e2la-
	      bel(8)  utility,	or for XFS using xfs_admin(8), or for reiserfs
	      using reiserfstune(8).

       -n, --no-mtab
	      Mount without writing in /etc/mtab.  This	is necessary for exam-
	      ple when /etc is on a read-only filesystem.

       -c, --no-canonicalize
	      Don't  canonicalize  paths.  The mount command canonicalizes all
	      paths (from command line	or  fstab)  and	 stores	 canonicalized
	      paths  to	 the  /etc/mtab	file. This option can be used together
	      with the -f flag for already canonicalized absolute paths.

       -s     Tolerate sloppy mount options rather than	failing. This will ig-
	      nore  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.

       --source	src
	      If only one argument for the mount command is given then the ar-
	      gument might be interpreted as  target  (mountpoint)  or	source
	      (device).	This option allows to explicitly define	that the argu-
	      ment is mount source.

       -r, --read-only
	      Mount the	filesystem 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 or ext4 will	replay its journal if the filesystem is	dirty.
	      To prevent this kind of write access, you	may want to mount ext3
	      or ext4 filesystem with "ro,noload" mount	 options  or  set  the
	      block device to read-only	mode, see command blockdev(8).

       -w, --rw, --read-write
	      Mount  the filesystem read/write.	This is	the default. A synonym
	      is -o rw.

       -L, --label label
	      Mount the	partition that has the specified label.

       -U, --uuid uuid
	      Mount the	partition that has the specified uuid.	These two  op-
	      tions  require  the  file	 /proc/partitions (present since Linux
	      2.1.116) to exist.

       -T, --fstab path
	      Specifies	alternative fstab file.	If the path is directory  then
	      the  files  in  the directory are	sorted by strverscmp(3), files
	      that starts with "." or without .fstab  extension	 are  ignored.
	      The  option  can	be  specified  more  than once.	This option is
	      mostly designed for initramfs or chroot scripts where additional
	      configuration  is	 specified  outside standard system configura-

	      Note  that  mount(8)  does  not  pass  the  option  --fstab   to
	      /sbin/mount.<type>  helpers, it means that the alternative fstab
	      files will be invisible for the helpers. This is no problem  for
	      normal  mounts,  but user	(non-root) mounts always require fstab
	      to verify	user's rights.

       -t, --types vfstype
	      The argument following the -t is used to indicate	the filesystem
	      type.   The  filesystem  types which are currently supported in-
	      clude: adfs, affs, autofs, cifs,	coda,  coherent,  cramfs,  de-
	      bugfs,  devpts,  efs, ext, ext2, ext3, ext4, hfs,	hfsplus, hpfs,
	      iso9660, jfs, minix, msdos, ncpfs, nfs, nfs4, ntfs, proc,	 qnx4,
	      ramfs,  reiserfs,	 romfs,	 squashfs,  smbfs, sysv, tmpfs,	ubifs,
	      udf, ufs,	umsdos,	usbfs, vfat, xenix, xfs, xiafs.	 Note that co-
	      herent,  sysv and	xenix are equivalent and that xenix and	coher-
	      ent will be removed at some point	in the future -- use sysv  in-
	      stead.  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 ker-

	      The programs mount and umount support filesystem subtypes.   The
	      subtype	is   defined   by   '.subtype'	suffix.	  For  example
	      'fuse.sshfs'. It's recommended to	use  subtype  notation	rather
	      than  add	any prefix to the mount	source (for example 'sshfs#ex-' is depreacated).

	      For most types all the mount program has to do is	issue a	simple
	      mount(2)	system call, and no detailed knowledge of the filesys-
	      tem type is required.  For a few types however (like nfs,	 nfs4,
	      cifs,  smbfs,  ncpfs)  ad	 hoc code is necessary.	The nfs, nfs4,
	      cifs, smbfs, and ncpfs filesystems have a	 separate  mount  pro-
	      gram.  In	order to make it possible to treat all types in	a uni-
	      form way,	mount will execute the	program	 /sbin/mount.TYPE  (if
	      that exists) when	called with type TYPE.	Since various versions
	      of the smbmount  program	have  different	 calling  conventions,
	      /sbin/mount.smbfs	may have to be a shell script that sets	up the
	      desired call.

	      If no -t option is given,	or if  the  auto  type	is  specified,
	      mount  will try to guess the desired type.  Mount	uses the blkid
	      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. All  of  the  filesystem
	      types will be mounted with mount option "silent".

	      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.

	      More than	one type may be	specified in a comma  separated	 list.
	      The  list	of filesystem types can	be prefixed with no to specify
	      the filesystem 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 filesystems except those of type msdos	and ext.

       --target	dir
	      If only one argument for the mount command is given then the ar-
	      gument might be interpreted as  target  (mountpoint)  or	source
	      (device).	This option allows to explicitly define	that the argu-
	      ment is mount target.

       -O, --test-opts opts
	      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-

		     mount -a -O no_netdev

	      mounts  all filesystems except those which have the option _net-
	      dev specified in the options field in the	/etc/fstab file.

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

	      The -t and -O options are	cumulative in  effect;	that  is,  the

		     mount -a -t ext2 -O _netdev

	      mounts  all  ext2	 filesystems  with the _netdev option, not all
	      filesystems that are either ext2	or  have  the  _netdev	option

       -o, --options opts
	      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

       -B, --bind
	      Remount  a  subtree  somewhere  else  (so	 that its contents are
	      available	in both	places). See above.

       -R, --rbind
	      Remount a	subtree	and all	possible submounts somewhere else  (so
	      that its contents	are available in both places). See above.

       -M, --move
	      Move a subtree to	some other place. See above.

       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

       The following options apply to any filesystem  that  is	being  mounted
       (but  not every filesystem 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 filesystem	should be  done	 asynchronously.  (See
	      also the sync option.)

       atime  Do  not  use noatime feature, then the inode access time is con-
	      trolled by kernel	defaults. See also the description for	stric-
	      tatime and relatime mount	options.

	      Do  not  update inode access times on this filesystem (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	filesystem to be mounted).

       context=context,	 fscontext=context,  defcontext=context	 and  rootcon-
	      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-

	      A	 commonly  used	 option	 for  removable	media is context="sys-

	      Two other	options	are fscontext= and defcontext=,	both of	 which
	      are mutually exclusive of	the context option. This means you can
	      use fscontext and	defcontext with	each other, but	neither	can be
	      used with	context.

	      The  fscontext=  option works for	all filesystems, regardless of
	      their xattr support. The fscontext option	sets  the  overarching
	      filesystem label to a specific security context. This filesystem
	      label is separate	from the individual labels on  the  files.  It
	      represents the entire filesystem for certain kinds of permission
	      checks, such as during mount or file creation.  Individual  file
	      labels  are  still  obtained  from the xattrs on the files them-
	      selves. The context option actually sets the  aggregate  context
	      that fscontext provides, in addition to supplying	the same label
	      for individual files.

	      You can set the default security context for unlabeled files us-
	      ing  defcontext=	option.	This overrides the value set for unla-
	      beled files in the policy	and requires a	filesystem  that  sup-
	      ports xattr labeling.

	      The  rootcontext=	option allows you to explicitly	label the root
	      inode of a FS being mounted before that FS or inode becomes vis-
	      ible  to userspace.  This	was found to be	useful for things like
	      stateless	linux.

	      Note that	the kernel rejects any remount request	that  includes
	      the  context  option,  even when unchanged from the current con-

	      Warning: the context value might contain commas, in  which  case
	      the value	has to be properly quoted, otherwise mount(8) will in-
	      terpret the comma	as a separator between mount  options.	 Don't
	      forget  that the shell strips off	quotes and thus	double quoting
	      is required.  For	example:

		     mount  -t	tmpfs  none  /mnt  -o	'context="system_u:ob-

	      For more details,	see selinux(8).

	      Use  default  options:  rw,  suid,  dev, exec, auto, nouser, and

       dev    Interpret	character or block special devices on the filesystem.

       nodev  Do not interpret character or block special devices on the  file

	      Update  directory	inode access times on this filesystem. This is
	      the default.

	      Do not update directory inode access times on this filesystem.

	      All directory updates within the filesystem 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
	      filesystem.   (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 filesystem
	      if one of	his groups matches the group of	the device.  This  op-
	      tion  implies 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  field  will  be

	      Do not increment the i_version inode field.

       mand   Allow mandatory locks on this filesystem.	See fcntl(2).

       nomand Do not allow mandatory locks on this filesystem.

	      The  filesystem resides on a device that requires	network	access
	      (used to prevent the  system  from  attempting  to  mount	 these
	      filesystems until	the network has	been enabled on	the system).

       nofail Do not report errors for this device if it does not exist.

	      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-

	      Since Linux 2.6.30, the kernel defaults to the behavior provided
	      by this option (unless noatime was  specified), and the stricta-
	      time option is required to obtain	traditional semantics. In  ad-
	      dition,  since  Linux 2.6.30, the	file's last access time	is al-
	      ways  updated  if	 it  is	more than 1 day	old.

	      Do not use relatime feature. See also the	strictatime mount  op-

	      Allows  to  explicitly requesting	full atime updates. This makes
	      it possible for kernel to	defaults to relatime  or  noatime  but
	      still allow userspace to override	it. For	more details about the
	      default system mount options see /proc/mounts.

	      Use the kernel's default behaviour for  inode  access  time  up-

       suid   Allow  set-user-identifier  or set-group-identifier bits to take

       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.)

       silent Turn on the silent flag.

       loud   Turn off the silent flag.

       owner  Allow an ordinary	(i.e., non-root) user to mount the  filesystem
	      if  he  is the owner of the device.  This	option implies the op-
	      tions nosuid and nodev (unless overridden	by subsequent options,
	      as in the	option line owner,dev,suid).

	      Attempt  to remount an already-mounted filesystem.  This is com-
	      monly used to change the mount flags  for	 a  filesystem,	 espe-
	      cially  to  make	a  readonly  filesystem	 writable. 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 op-
	      tions with options from command line ( -o	).

       ro     Mount the	filesystem read-only.

       rw     Mount the	filesystem read-write.

       sync   All I/O to the filesystem	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.

       user   Allow an ordinary	user to	mount the filesystem.  The name	of the
	      mounting	user  is  written  to  mtab so that he can unmount the
	      filesystem again.	 This option implies the options  noexec,  no-
	      suid,  and nodev (unless overridden by subsequent	options, as in
	      the option line user,exec,dev,suid).

       nouser Forbid an	ordinary (i.e.,	non-root) user to mount	 the  filesys-
	      tem.  This is the	default.

       users  Allow  every user	to mount and unmount the filesystem.  This op-
	      tion implies the options noexec, nosuid, and nodev (unless over-
	      ridden   by   subsequent	 options,   as	 in  the  option  line

       x-*    All options prefixed with	"x-" are interpreted  as  comments  or
	      userspace	 applications  specific	options. These options are not
	      stored to	mtab file, send	to mount.<type>	 helpers  or  mount(2)
	      system  call. The	suggested format is x-<appname>.<option> (e.g.

	      Allow to make a target directory (mountpoint). The optional  ar-
	      gument  <mode>  specifies	 the  file system access mode used for
	      mkdir (2)	in octal notation. The	default	 mode  is  0755.  This
	      functionality is supported only for root users.

       The  following options apply only to certain filesystems.  We sort them
       by filesystem. 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-

Mount options for adfs
       uid=value and gid=value
	      Set the owner and	group of the files in the filesystem (default:

       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-

Mount options for affs
       uid=value and gid=value
	      Set the owner and	group of the root of the filesystem  (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.

	      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.

	      Do not allow any changes to the protection bits on the  filesys-

       usemp  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 used before volume	name, when following a link.

	      Prefix  (of  length at most 30) used before '/' when following a
	      symbolic link.

	      (Default:	2.) Number of unused blocks at the start  of  the  de-

	      Give explicitly the location of the root block.

	      Give blocksize. Allowed values are 512, 1024, 2048, 4096.

	      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 (cifs-utils pack-
       age must	be installed).

Mount options for coherent

Mount options for debugfs
       The debugfs filesystem is a pseudo filesystem, traditionally mounted on
       /sys/kernel/debug.  As of kernel	version	3.4, debugfs has the following

       uid=n, gid=n
	      Set the owner and	group of the mountpoint.

	      Sets the mode of the mountpoint.

Mount options for devpts
       The  devpts filesystem is a pseudo filesystem, 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

       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.

	      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.

	      Create  a	 private  instance of devpts filesystem, such that in-
	      dices of ptys allocated in this new instance are independent  of
	      indices created in other instances of devpts.

	      All  mounts  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.

	      This  option  is	mainly used to support containers in the linux
	      kernel. It is implemented	in linux kernel	versions starting with
	      2.6.29.	Further, this mount option is valid only if CONFIG_DE-
	      VPTS_MULTIPLE_INSTANCES is enabled in the	kernel configuration.

	      To use this option effectively, /dev/ptmx	 must  be  a  symbolic
	      link  to	pts/ptmx.  See Documentation/filesystems/devpts.txt in
	      the linux	kernel source tree for details.


	      Set the mode for the new ptmx device node	in the devpts filesys-

	      With  the	 support  for multiple instances of devpts (see	newin-
	      stance 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
	      mode of the new ptmx node	is 0000.  ptmxmode=value  specifies  a
	      more  useful  mode  for  the ptmx	node and is highly recommended
	      when the newinstance option is specified.

	      This option is only implemented in linux kernel versions	start-
	      ing with 2.6.29. Further this option is valid only if CONFIG_DE-
	      VPTS_MULTIPLE_INSTANCES is enabled in the	kernel configuration.

Mount options for ext
       None.  Note that	the `ext' filesystem 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'  filesystem	is the standard	Linux filesystem.  Since Linux
       2.5.46, for most	 mount	options	 the  default  is  determined  by  the
       filesystem superblock. Set them with tune2fs(8).

	      Support POSIX Access Control Lists (or not).

	      Set the behaviour	for the	statfs system call. The	minixdf	behav-
	      iour is to return	in the f_blocks	 field	the  total  number  of
	      blocks  of  the  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 -o minixdf; df	/k; umount /k
	      Filesystem   1024-blocks	Used Available Capacity	Mounted	on
	      /dev/sda6	     2630655   86954  2412169	   3%	/k
	      %	mount /k -o bsddf; df /k; umount /k
	      Filesystem   1024-blocks	Used Available Capacity	Mounted	on
	      /dev/sda6	     2543714	  13  2412169	   0%	/k

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

       check=none or 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.  The   non-default   behavior   is   unsupported
	      (check=normal  and check=strict options have been	removed). Note
	      that these mount options don't have to be	supported if ext4 ker-
	      nel driver is used for ext2 and ext3 filesystems.

       debug  Print debugging info upon	each (re)mount.

	      Define  the behaviour when an error is encountered.  (Either ig-
	      nore errors and just mark	the filesystem erroneous and continue,
	      or  remount the filesystem read-only, or panic and halt the sys-
	      tem.)  The default is set	in the filesystem superblock, and  can
	      be changed using tune2fs(8).

       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.

	      The usrquota (same as quota) mount  option  enables  user	 quota
	      support  on  the	filesystem. grpquota enables group quotas sup-
	      port. You	need the quota utilities to actually enable and	manage
	      the quota	system.

	      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

       resgid=n	and resuid=n
	      The  ext2	filesystem 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

       sb=n   Instead  of  block  1,  use block	n as superblock. This could be
	      useful when the filesystem has been damaged.   (Earlier,	copies
	      of  the  superblock would	be made	every 8192 blocks: in block 1,
	      8193, 16385, ... (and one	got  thousands	of  copies  on	a  big
	      filesystem).  Since  version  1.08,  mke2fs has a	-s (sparse su-
	      perblock)	option to reduce the number of backup superblocks, and
	      since  version 1.15 this is the default. Note that this may mean
	      that ext2	filesystems created  by	 a  recent  mke2fs  cannot  be
	      mounted  r/w  under Linux	2.0.*.)	 The block number here uses 1k
	      units. Thus, if you  want	 to  use  logical  block  32768	 on  a
	      filesystem with 4k blocks, use "sb=131072".

	      Support "user." extended attributes (or not).

Mount options for ext3
       The  ext3 filesystem is a version of the	ext2 filesystem	which has been
       enhanced	with journaling.  It supports the same options as ext2 as well
       as the following	additions:

	      Update the ext3 filesystem's journal to the current format.

	      When  a  journal	already	exists,	this option is ignored.	Other-
	      wise, it specifies the number of the inode which will  represent
	      the  ext3	 filesystem's  journal	file;	ext3 will create a new
	      journal, overwriting the old contents of the  file  whose	 inode
	      number is	inum.

	      When  the	 external  journal  device's  major/minor numbers have
	      changed, this option allows the user to specify the new  journal
	      location.	  The journal device is	identified through its new ma-
	      jor/minor	numbers	encoded	in devnum.

	      Don't load the journal on	mounting.  Note	that if	the filesystem
	      was not unmounted	cleanly, skipping the journal replay will lead
	      to the filesystem	containing inconsistencies that	 can  lead  to
	      any number of problems.

	      Specifies	the journaling mode for	file data.  Metadata is	always
	      journaled.  To use modes other than ordered on the root filesys-
	      tem,  pass the mode to the kernel	as boot	parameter, e.g.	 root-

		     All data is committed into	the  journal  prior  to	 being
		     written into the main filesystem.

		     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.

		     Data ordering is not preserved - data may be written into
		     the main filesystem after its metadata has	been committed
		     to	 the  journal.	 This  is  rumoured to be the highest-
		     throughput	option.	 It guarantees internal	filesystem in-
		     tegrity, however it can allow old data to appear in files
		     after a crash and journal recovery.

       barrier=0 / barrier=1
	      This enables/disables barriers.	barrier=0  disables  it,  bar-
	      rier=1 enables it.  Write	barriers enforce proper	on-disk	order-
	      ing of journal commits, making volatile disk write  caches  safe
	      to  use,	at some	performance penalty.  The ext3 filesystem does
	      not enable write barriers	by default.  Be	sure to	enable	barri-
	      ers  unless  your	 disks	are battery-backed one way or another.
	      Otherwise	you risk filesystem corruption in case of power	 fail-

	      Sync  all	 data  and  metadata  every nrsec seconds. The default
	      value is 5 seconds. Zero means default.

	      Enable Extended User Attributes. See the attr(5) manual page.

       acl    Enable POSIX Access Control Lists. See the acl(5)	manual page.

	      Apart from the old quota system (as in  ext2,  jqfmt=vfsold  aka
	      version  1 quota)	ext3 also supports journaled quotas (version 2
	      quota). jqfmt=vfsv0 enables journaled quotas. For	journaled quo-
	      tas    the   mount   options   usrjquota=aquota.user   and   gr- are required	to tell	the quota system which
	      quota database files to use. Journaled quotas have the advantage
	      that even	after a	crash no quota check is	required.

Mount options for ext4
       The ext4	filesystem is an advanced level	of the ext3  filesystem	 which
       incorporates  scalability  and  reliability enhancements	for supporting
       large filesystem.

       The  options  journal_dev,  noload,  data,  commit,  orlov,   oldalloc,
       [no]user_xattr [no]acl, bsddf, minixdf, debug, errors, data_err,	grpid,
       bsdgroups, nogrpid sysvgroups, resgid, resuid, sb, quota, noquota,  gr-
       pquota, usrquota	usrjquota, grpjquota and jqfmt are backwardly compati-
       ble with	ext3 or	ext2.

	      Enable checksumming of the journal transactions.	This will  al-
	      low the recovery code in e2fsck and the kernel to	detect corrup-
	      tion in the kernel.  It is a compatible change and will  be  ig-
	      nored by older kernels.

	      Commit block can be written to disk without waiting for descrip-
	      tor blocks. If enabled older kernels cannot  mount  the  device.
	      This will	enable 'journal_checksum' internally.

       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 a
	      barrier write, it	will disable again with	a warning.  Write bar-
	      riers enforce proper on-disk ordering of journal commits,	making
	      volatile disk write caches safe to use, at some performance pen-
	      alty.   If  your disks are battery-backed	in one way or another,
	      disabling	barriers may safely improve  performance.   The	 mount
	      options  "barrier" and "nobarrier" can also be used to enable or
	      disable barriers,	for consistency	with other ext4	mount options.

	      The ext4 filesystem enables write	barriers by default.

	      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 value	must be	a power	of 2. The  de-
	      fault value is 32	blocks.

	      Number of	filesystem blocks that mballoc will try	to use for al-
	      location size and	alignment. For RAID5/6 systems this should  be
	      the number of data disks * RAID chunk size in filesystem blocks.

	      Deferring	block allocation until write-out time.

	      Disable  delayed	allocation.  Blocks are	allocated when data is
	      copied from user to page cache.

	      Maximum amount of	time ext4 should wait for additional  filesys-
	      tem operations to	be batch together with a synchronous write op-
	      eration. Since a synchronous write operation is going to force 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
	      the synchronous write. The algorithm used	is designed  to	 auto-
	      matically	 tune  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 transaction has been running is less than the	 commit	 time,
	      ext4 will	try sleeping for the commit time to see	if other oper-
	      ations will join the transaction.	The commit time	is  capped  by
	      the max_batch_time, which	defaults to 15000us (15ms). This opti-
	      mization can be turned off entirely by setting max_batch_time to

	      This  parameter  sets the	commit time (as	described above) to be
	      at least min_batch_time. It defaults to zero  microseconds.  In-
	      creasing	this  parameter	 may  improve the throughput of	multi-
	      threaded,	synchronous workloads on very fast disks, at the  cost
	      of increasing latency.

	      The  I/O priority	(from 0	to 7, where 0 is the highest priority)
	      which should be used for I/O operations submitted	by  kjournald2
	      during  a	 commit	 operation.   This  defaults  to 3, which is a
	      slightly higher priority than the	default	I/O priority.

       abort  Simulate the effects of calling ext4_abort() for debugging  pur-
	      poses.   This  is	 normally  used	 while remounting a filesystem
	      which is already mounted.

	      Many broken applications don't use fsync() when replacing	exist-
	      ing files	via patterns such as

	      fd  =  open("")/write(fd,..)/close(fd)/ rename("",

	      or worse yet

	      fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).

	      If auto_da_alloc is enabled, ext4	will detect  the  replace-via-
	      rename  and replace-via-truncate patterns	and force that any de-
	      layed allocation blocks are allocated  such  that	 at  the  next
	      journal  commit,	in  the	 default  data=ordered	mode, the data
	      blocks of	the new	file are forced	to disk	 before	 the  rename()
	      operation	is committed.  This provides roughly the same level of
	      guarantees as ext3, and avoids the  "zero-length"	 problem  that
	      can  happen  when	a system crashes before	the delayed allocation
	      blocks are forced	to disk.

	      Controls whether ext4 should issue discard/TRIM commands to  the
	      underlying  block	 device	when blocks are	freed.	This is	useful
	      for SSD devices and sparse/thinly-provisioned LUNs,  but	it  is
	      off by default until sufficient testing has been done.

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

       resize Allows to	resize filesystem to the  end  of  the	last  existing
	      block group, further resize has to be done with resize2fs	either
	      online, or offline. It can be used only  with  conjunction  with

	      This  options  allows to enables/disables	the in-kernel facility
	      for tracking filesystem metadata	blocks	within	internal  data
	      structures.  This	 allows	 multi-	block allocator	and other rou-
	      tines  to	 quickly  locate  extents  which  might	 overlap  with
	      filesystem  metadata  blocks. This option	is intended for	debug-
	      ging purposes and	since it negatively affects  the  performance,
	      it is off	by default.

	      Controls whether or not ext4 should use the DIO read locking. If
	      the dioread_nolock option	is specified ext4 will allocate	unini-
	      tialized	extent	before	buffer write and convert the extent to
	      initialized after	IO completes.  This approach allows ext4  code
	      to  avoid	 using inode mutex, which improves scalability on high
	      speed storages. However this does	not work with data  journaling
	      and  dioread_nolock  option will be ignored with kernel warning.
	      Note that	dioread_nolock code path is only used for extent-based
	      files.  Because of the restrictions this options comprises it is
	      off by default (e.g. dioread_lock).

	      Enable 64-bit inode version support. This	option is off  by  de-

Mount options for fat
       (Note:  fat  is not a separate filesystem, but a	common part of the ms-
       dos, umsdos and vfat filesystems.)

	      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.)

	      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.

	      Set  the	umask applied to directories only.  The	default	is the
	      umask of the current process.  The value is given	in octal.

	      Set the umask applied to regular files only.  The	default	is the
	      umask of the current process.  The value is given	in octal.

	      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 inflexible. With
	      this option you can relax	it.

	      Three different levels of	pickyness can be chosen:

		     Upper and lower case are accepted	and  equivalent,  long
		     name  parts  are truncated	(e.g.  verylongname.foobar be-
		     comes, leading and embedded spaces are  ac-
		     cepted in each name part (name and	extension).

		     Like  "relaxed",  but  many  special characters (*, ?, <,
		     spaces, etc.) are rejected.  This is the default.

		     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,

	      Sets  the	codepage for converting	to shortname characters	on FAT
	      and VFAT filesystems. By default,	codepage 437 is	used.

	      The fat filesystem can perform CRLF<-->NL	(MS-DOS	text format to
	      UNIX  text  format) conversion in	the kernel. The	following con-
	      version modes are	available:

	      binary no	translation is performed.  This	is the default.

	      text   CRLF<-->NL	translation is performed on all	files.

	      auto   CRLF<-->NL	translation is performed  on  all  files  that
		     don't  have  a "well-known	binary"	extension. The list of
		     known  extensions	can  be	 found	at  the	 beginning  of
		     fs/fat/misc.c  (as	 of  2.0,  the list is:	exe, com, bin,
		     app, sys, drv, ovl, ovr, obj, lib,	dll,  pif,  arc,  zip,
		     lha,  lzh,	 zoo, tar, z, arj, tz, taz, tzp, tpz, gz, tgz,
		     deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf,	gf,  pk,  pxl,

	      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 filesystems mounted in binary	mode, a	conversion tool	(from-
	      dos/todos) is available. This option is obsolete.

	      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.  This option	is obsolete.

	      Option passed to the CVF module. This option is obsolete.

       debug  Turn on the debug	flag.  A version string	and a list of filesys-
	      tem parameters will be printed (these data are also  printed  if
	      the parameters appear to be inconsistent).

	      If  set,	causes discard/TRIM commands to	be issued to the block
	      device when blocks are freed. This is useful for SSD devices and
	      sparse/thinly-provisioned	LUNs.

	      Specify  a  12,  16 or 32	bit fat.  This overrides the automatic
	      FAT type detection routine.  Use with caution!

	      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.

       nfs    If set, enables in-memory	indexing of directory inodes to	reduce
	      the  frequency of	ESTALE errors in NFS client operations.	Useful
	      only when	the filesystem is exported via NFS.

       tz=UTC This option disables the conversion of timestamps	between	 local
	      time  (as	 used by Windows on FAT) and UTC (which	Linux uses in-
	      ternally).  This is particularly 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!

	      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.

	      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.

	      Use the "free clusters" value stored on FSINFO. It'll be used to
	      determine	number of free clusters	 without  scanning  disk.  But
	      it's not used by default,	because	recent Windows don't update it
	      correctly	in 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
	      Set the creator/type values as shown by the  MacOS  finder  used
	      for creating new files.  Default values: '????'.

       uid=n, gid=n
	      Set the owner and	group of all files.  (Default: the uid and gid
	      of the current process.)

       dir_umask=n, file_umask=n, umask=n
	      Set the umask used for all directories, all  regular  files,  or
	      all files	and directories.  Defaults to the umask	of the current

	      Select the CDROM session to mount.  Defaults to leaving that de-
	      cision to	the CDROM driver.  This	option will fail with anything
	      but a CDROM as underlying	device.

       part=n Select partition number n	from the device.  Only makes sense for
	      CDROMs.  Defaults	to not parsing the partition table at all.

       quiet  Don't complain about invalid mount options.

Mount options for hpfs
       uid=value and gid=value
	      Set  the owner and group of all files. (Default: the uid and gid
	      of the current process.)

	      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.

	      Convert all files	names to lower case, or	leave them.  (Default:

	      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=bi-
	      nary, just read what is in the file. This	is the default.

	      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  re-
       strictions  on  filename	length), and in	addition all characters	are in
       upper case.  Also there is no field  for	 file  ownership,  protection,
       number of links,	provision for block/character devices, etc.

       Rock  Ridge is an extension to iso9660 that provides all	of these UNIX-
       like features.  Basically there are extensions to each directory	record
       that  supply  all of the	additional information,	and when Rock Ridge is
       in use, the filesystem is indistinguishable from	a normal UNIX filesys-
       tem (except that	it is read-only, of course).

       norock Disable the use of Rock Ridge extensions,	even if	available. Cf.

	      Disable the use of Microsoft Joliet extensions, even  if	avail-
	      able. Cf.	map.

	      With  check=relaxed, a filename is first converted to lower case
	      before doing the lookup.	This is	probably only  meaningful  to-
	      gether 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,
	      possibly overriding the information found	in the Rock Ridge  ex-
	      tensions.	 (Default: uid=0,gid=0.)

	      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.

	      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.)

	      Set  the	block  size  to	 the   indicated   value.    (Default:

	      (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.

	      Select number of session on multisession CD. (Since 2.3.4.)

	      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-

	      Character	set to use for converting 16 bit Unicode characters on
	      CD to 8 bit characters. The default is iso8859-1.

       utf8   Convert 16 bit Unicode characters	on CD to UTF-8.

Mount options for jfs
	      Character	set to use for converting from Unicode to ASCII.   The
	      default  is  to  do  no conversion.  Use iocharset=utf8 for UTF8
	      translations.  This requires CONFIG_NLS_UTF8 to be  set  in  the
	      kernel .config file.

	      Resize  the  volume to value blocks. JFS only supports growing a
	      volume, not shrinking it.	This option is only valid during a re-
	      mount, when the volume is	mounted	read-write. The	resize keyword
	      with no value will grow the volume to the	full size of the  par-

	      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 ends.

	      Default.	Commit metadata	changes	to the journal.	 Use this  op-
	      tion to remount a	volume where the nointegrity option was	previ-
	      ously specified in order to restore normal behavior.

	      Define the behaviour when	an error is encountered.  (Either  ig-
	      nore errors and just mark	the filesystem erroneous and continue,
	      or remount the filesystem	read-only, or panic and	halt the  sys-

	      These options are	accepted but ignored.

Mount options for minix

Mount options for msdos
       See  mount  options for fat.  If	the msdos filesystem detects an	incon-
       sistency, it reports an error and sets the file system  read-only.  The
       filesystem can be made writable 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-utils 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.

Mount options for ntfs
	      Character	set to use when	returning file	names.	 Unlike	 VFAT,
	      NTFS  suppresses	names  that contain nonconvertible characters.

	      New name for the option earlier called iocharset.

       utf8   Use UTF-8	for converting file names.

	      For 0 (or	`no' or	`false'), do not use escape sequences for  un-
	      known  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 en-

	      If enabled (posix=1), the	filesystem distinguishes between upper
	      and  lower case. The 8.3 alias names are presented as hard links
	      instead of being suppressed. This	option is obsolete.

       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

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

Mount options for reiserfs
       Reiserfs	is a journaling	filesystem.

       conv   Instructs	 version  3.6 reiserfs software	to mount a version 3.5
	      filesystem, using	the 3.6	format for newly created objects. This
	      filesystem will no longer	be compatible with reiserfs 3.5	tools.

	      Choose  which  hash  function  reiserfs  will  use to find files
	      within directories.

		     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.

	      r5     A modified	version	of the rupasov hash. It	is used	by de-
		     fault 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	in use
		     by	examining the filesystem being mounted,	 and to	 write
		     this  information	into  the reiserfs superblock. This is
		     only useful on the	first mount of an old format  filesys-

	      Tunes the	block allocator. This may provide performance improve-
	      ments in some situations.

	      Tunes the	block allocator. This may provide performance improve-
	      ments in some situations.

	      Disable  the border allocator algorithm invented by Yury Yu. Ru-
	      pasov.  This may provide performance improvements	in some	situa-

       nolog  Disable  journaling.  This  will	provide	slight performance im-
	      provements in some situations at the cost	of  losing  reiserfs's
	      fast  recovery  from  crashes.  Even with	this option turned on,
	      reiserfs still performs all journaling operations, save for  ac-
	      tual  writes  into its journaling	area.  Implementation of nolog
	      is a work	in progress.

       notail By default, reiserfs stores small	files  and  `file  tails'  di-
	      rectly  into  its	 tree.	This  confuses	some utilities such as
	      LILO(8).	This option is used to disable packing of  files  into
	      the tree.

	      Replay the transactions which are	in the journal,	but do not ac-
	      tually mount the filesystem. Mainly used by reiserfsck.

	      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

	      Enable Extended User Attributes. See the attr(5) manual page.

       acl    Enable POSIX Access Control Lists. See the acl(5)	manual page.

       barrier=none / barrier=flush
	      This  enables/disables the use of	write barriers in the journal-
	      ing code.	 barrier=none disables it, barrier=flush  enables  it.
	      Write  barriers  enforce proper on-disk ordering of journal com-
	      mits, making volatile disk write caches safe  to	use,  at  some
	      performance  penalty.  The  reiserfs  filesystem does not	enable
	      write barriers by	default. Be sure  to  enable  barriers	unless
	      your  disks are battery-backed one way or	another. Otherwise you
	      risk filesystem corruption in case of power failure.

Mount options for romfs

Mount options for squashfs

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

Mount options for tmpfs
	      Override	default	 maximum  size of the filesystem.  The size is
	      given in bytes, and rounded up to	entire pages.  The default  is
	      half  of	the memory. The	size parameter also accepts a suffix %
	      to limit this tmpfs instance to that percentage of your physical
	      RAM:  the	default, when neither size nor nr_blocks is specified,
	      is size=50%

	      The same as size,	but in blocks of PAGE_CACHE_SIZE

	      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

       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.

	      Set  the NUMA memory allocation policy for all files in that in-
	      stance (if the kernel CONFIG_NUMA	is enabled) - which can	be ad-
	      justed on	the fly	via 'mount -o remount ...'

		     prefers to	allocate memory	from the local node

		     prefers to	allocate memory	from the given Node

		     allocates memory only from	nodes in NodeList

		     prefers to	allocate from each node	in turn

		     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 sys-
	      tem  relies  on  that tmpfs being	mounted, but from time to time
	      runs a kernel built without NUMA capability (perhaps a safe  re-
	      covery kernel), or with fewer nodes online, then it is advisable
	      to omit the mpol option from automatic mount options.  It	can be
	      added later, when	the tmpfs is already mounted on	MountPoint, by
	      'mount -o	remount,mpol=Policy:NodeList MountPoint'.

Mount options for ubifs
       UBIFS is	a flash	file system which works	on top of  UBI	volumes.  Note
       that atime is not supported and is always turned	off.

       The device name may be specified	as
	      ubiX_Y UBI device	number X, volume number	Y

	      ubiY   UBI device	number 0, volume number	Y

		     UBI device	number X, volume with name NAME

		     UBI device	number 0, volume with name NAME
       Alternative !  separator	may be used instead of :.

       The following mount options are available:

	      Enable  bulk-read.  VFS  read-ahead is disabled because it slows
	      down the file system. Bulk-Read  is  an  internal	 optimization.
	      Some  flashes  may  read	faster if the data are read at one go,
	      rather than at several read requests. For	example,  OneNAND  can
	      do "read-while-load" if it reads more than one NAND page.

	      Do not bulk-read.	This is	the default.

	      Check data CRC-32	checksums. This	is the default.

	      Do  not  check  data  CRC-32  checksums.	With  this option, the
	      filesystem does not check	CRC-32 checksum	for data, but it  does
	      check it for the internal	indexing information. This option only
	      affects reading, not writing. CRC-32 is always  calculated  when
	      writing the data.

	      Select  the  default compressor which is used when new files are
	      written. It is  still  possible  to  read	 compressed  files  if
	      mounted with the none option.

Mount options for udf
       udf  is	the  "Universal	Disk Format" filesystem	defined	by the Optical
       Storage Technology Association, and is often  used  for	DVD-ROM.   See
       also iso9660.

       gid=   Set the default group.

       umask= Set the default umask.  The value	is given in octal.

       uid=   Set the default user.

       unhide Show otherwise hidden files.

	      Show deleted files in lists.

	      Unset strict conformance.

	      Set the NLS character set.

       bs=    Set the block size. (May not work	unless 2048.)

       novrs  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)

	      Override the PartitionDesc location. (unused)

	      Set the last block of the	filesystem.

	      Override the fileset block location. (unused)

	      Override the root	directory location. (unused)

Mount options for ufs
	      UFS  is a	filesystem 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	 (Net-

	      ufs2   Used in FreeBSD 5.x supported as read-write.

	      5xbsd  Synonym for ufs2.

	      sun    For filesystems created by	SunOS or Solaris on Sparc.

	      sunx86 For filesystems created by	Solaris	on x86.

	      hp     For filesystems created by	HP-UX, read-only.

		     For  filesystems  created	by  NeXTStep (on NeXT station)
		     (currently	read only).

		     For NextStep CDROMs (block_size ==	2048), read-only.

		     For  filesystems  created	by  OpenStep  (currently  read
		     only).   The  same	filesystem type	is also	used by	Mac OS

	      Set behaviour on error:

	      panic  If	an error is encountered, cause a kernel	panic.

		     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

Mount options for vfat
       First of	all, the mount options for fat are recognized.	The dotsOK op-
       tion is explicitly killed by vfat.  Furthermore,	there are

	      Translate	 unhandled  Unicode  characters	to special escaped se-
	      quences.	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.  This op-
	      tion is obsolete.

	      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 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.


	      Defines the behaviour for	 creation  and	display	 of  filenames
	      which fit	into 8.3 characters. If	a long name for	a file exists,
	      it will always be	preferred display. There are four modes: :

	      lower  Force the short name to lower case	upon display; store  a
		     long name when the	short name is not all upper case.

	      win95  Force  the	short name to upper case upon display; store a
		     long name when the	short name is not all upper case.

	      winnt  Display the shortname as is; store	a long name  when  the
		     short name	is not all lower case or all upper case.

	      mixed  Display  the short	name as	is; store a long name when the
		     short name	is not all upper case. This mode  is  the  de-
		     fault since Linux 2.6.32.

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 us-
	      bfs filesystem (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 filesystem (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

Mount options for xfs
	      Sets the buffered	I/O end-of-file	preallocation size when	 doing
	      delayed  allocation  writeout.  Valid values for this option are
	      page size	(typically 4KiB) through to 1GiB, inclusive, in	power-
	      of-2 increments.

	      The  default  behaviour is for dynamic end-of-file preallocation
	      size, which uses a set of	heuristics to optimise the  prealloca-
	      tion  size  based	 on the	current	allocation patterns within the
	      file and the access patterns to the file.	Specifying a fixed al-
	      locsize value turns off the dynamic behaviour.

	      The  options enable/disable 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 when attr2	is se-
	      lected (either when setting or removing extended attributes) the
	      on-disk  superblock feature bit field will be updated to reflect
	      this format being	in use.

	      The default behaviour is determined by the on-disk  feature  bit
	      indicating  that	attr2 behaviour	is active. If either mount op-
	      tion it set, then	that becomes  the  new	default	 used  by  the

	      CRC enabled filesystems always use the attr2 format, and so will
	      reject the noattr2 mount option if it is set.

	      Enables/disables the use	of  block  layer  write	 barriers  for
	      writes into the journal and for data integrity operations.  This
	      allows for drive level write caching to be enabled, for  devices
	      that support write barriers.

	      Enable/disable  the  issuing of commands to let the block	device
	      reclaim space freed by the filesystem.  This is useful  for  SSD
	      devices, thinly provisioned LUNs and virtual machine images, but
	      may have a performance impact.

	      Note: It is currently recommended	that you use the fstrim	appli-
	      cation  to  discard  unused blocks rather	than the discard mount
	      option because the performance impact of this  option  is	 quite

	      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 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.

	      Make the data allocator  use  the	 filestreams  allocation  mode
	      across  the  entire  filesystem  rather than just	on directories
	      configured to use	it.

       When ikeep is specified,	XFS does not delete empty inode
	      clusters and keeps them around on	disk.  When noikeep is	speci-
	      fied, empty inode	clusters are returned to the free space	pool.

	      When  inode32  is	 specified, it indicates that XFS limits inode
	      creation to locations which will not  result  in	inode  numbers
	      with more	than 32	bits of	significance.

	      When  inode64  is	specified, it 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.

	      inode32 is provided for backwards	compatibility with older  sys-
	      tems  and	 applications, since 64	bits inode numbers might cause
	      problems for some	applications that cannot  handle  large	 inode
	      numbers.	 If  applications are in use which do not handle inode
	      numbers bigger than 32 bits, the inode32 option should be	speci-

	      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  ap-
	      plications  to avoid inefficient read/modify/write I/O.  This is
	      typically	the page size of the machine, as this is the granular-
	      ity of the page cache.

	      If  "largeio"  specified,	 a  filesystem that was	created	with 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. Otherwise the behaviour is	the same as if
	      "nolargeio" was specified.

	      Set the number of	in-memory log buffers.	 Valid	numbers	 range
	      from 2-8 inclusive.

	      The default value	is 8 buffers.

	      If  the  memory  cost of 8 log buffers is	too high on small sys-
	      tems, then it may	be reduced at  some  cost  to  performance  on
	      metadata intensive workloads. The	logbsize option	below controls
	      the size of each buffer and so is	also relevent to this case.

	      Set the size of each in-memory log  buffer.   The	 size  may  be
	      specified	 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 logbsize must be an integer
	      multiple of the log stripe unit configured at mkfs time.

	      The default value	for version 1 logs is 32768, while the default
	      value for	version	2 logs is MAX(32768, log_sunit).

	      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  op-
	      tional,  and  the	log section can	be separate from the data sec-
	      tion or contained	within it.

	      Data allocations will not	be aligned at stripe unit  boundaries.
	      This  is only relevant to	filesystems created with non-zero data
	      alignment	parameters (sunit, swidth) by mkfs.

	      The filesystem will be mounted without running log recovery.  If
	      the filesystem was not cleanly unmounted,	it is likely to	be in-
	      consistent when mounted in "norecovery" mode.  Some files	or di-
	      rectories	 may  not  be accessible because of this.  Filesystems
	      mounted "norecovery" must	be mounted read-only or	the mount will

       nouuid Don't  check for double mounted file systems using the file sys-
	      tem uuid.	 This is useful	to mount LVM snapshot volumes, and of-
	      ten used in combination with "norecovery"	for mounting read-only

	      Forcibly turns off all quota accounting and  enforcement	within
	      the filesystem.

	      User  disk quota accounting enabled, and limits (optionally) en-
	      forced.  Refer to	xfs_quota(8) for further details.

	      Group disk quota accounting enabled and limits (optionally)  en-
	      forced.  Refer to	xfs_quota(8) for further details.

	      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. These options are only relevant to	filesystems that  were
	      created with non-zero data alignment parameters.

	      The  sunit  and  swidth  parameters specified must be compatible
	      with the existing	filesystem alignment characteristics.  In gen-
	      eral,  that means	the only valid changes to sunit	are increasing
	      it by a power-of-2 multiple. Valid swidth	values are any integer
	      multiple of a valid sunit	value.

	      Typically	the only time these mount options are necessary	if af-
	      ter an underlying	RAID device has	had  it's  geometry  modified,
	      such as adding a new disk	to a RAID5 lun and reshaping it.

	      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.

       wsync  When specified, all filesystem namespace operations are executed
	      synchronously. This ensures that when  the  namespace  operation
	      (create,	unlink,	etc) completes,	the change to the namespace is
	      on stable	storage. This is useful	in HA  setups  where  failover
	      must not result in clients seeing	inconsistent namespace presen-
	      tation during or after a failover	event.

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.

       One further possible type is a mount via	the loop device. For  example,
       the command

	      mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop

       will  set  up  the  loop	 device	 /dev/loop3  to	correspond to the file
       /tmp/disk.img, and then mount this device on /mnt.

       If no explicit loop device is mentioned (but just an option  `-o	 loop'
       is  given), then	mount will try to find some unused loop	device and use
       that, for example

	      mount /tmp/disk.img /mnt -o loop

       The mount command automatically creates a loop device  from  a  regular
       file  if	 a filesystem type is not specified or the filesystem is known
       for libblkid, for example:

	      mount /tmp/disk.img /mnt

	      mount -t ext3 /tmp/disk.img /mnt

       This type of mount knows	about four options, namely  loop,  offset  and
       sizelimit  , that are really options to losetup(8).  (These options can
       be used in addition to those specific to	the filesystem type.)

       Since Linux 2.6.25 is supported auto-destruction	of  loop  devices  and
       then  any  loop device allocated	by mount will be freed by umount inde-
       pendently on /etc/mtab.

       You can also free a loop	device by hand,	using `losetup -d' or  `umount

       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

       The  command  mount  -a	returns	0 (all success), 32 (all failed) or 64
       (some failed, some success).

       The syntax of external mount helpers is:

	      /sbin/mount._suffix_ spec	dir [-sfnv] [-o	options] [-t type.sub-

       where  the <type> is filesystem type and	-sfnvo options have same mean-
       ing like	standard mount options.	The -t option is used  for filesystems
       with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs).

       /etc/fstab	 filesystem table

       /etc/mtab	 table of mounted filesystems

       /etc/mtab~	 lock file

       /etc/mtab.tmp	 temporary file

       /etc/filesystems	 a list	of filesystem types to try

	      overrides	the default location of	the fstab file

	      overrides	the default location of	the mtab file

	      enables debug output

       mount(2),   umount(2),	fstab(5),  umount(8),  swapon(8),  findmnt(8),
       nfs(5),	 xfs(5),   e2label(8),	 xfs_admin(8),	 mountd(8),   nfsd(8),
       mke2fs(8), tune2fs(8), losetup(8)

       It is possible for a corrupted filesystem to cause a crash.

       Some  Linux filesystems don't support -o	sync and -o dirsync (the ext2,
       ext3, fat and vfat 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 ext2fs-
       specific	parameters, except sb, are changeable with a remount, for  ex-
       ample, but you can't change gid or umask	for the	fatfs).

       It  is  possible	that files /etc/mtab and /proc/mounts don't match. The
       first file is based only	on the mount command options, but the  content
       of the second file also depends on the kernel and others	settings (e.g.
       remote NFS server. In particular	case the mount command may reports un-
       reliable	 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 re-
       sult due	to the lack of consistency check in kernel  even  if  noac  is

       The loop	option with the	offset or sizelimit options used may fail when
       using older kernels if the mount	command	can't confirm that the size of
       the  block  device has been configured as requested. This situation can
       be worked around	by using the losetup command manually  before  calling
       mount with the configured loop device.

       A mount command existed in Version 5 AT&T UNIX.

       Karel Zak <>

       The  mount  command  is part of the util-linux package and is available

util-linux			 January 2012			      MOUNT(8)

NAME | SYNOPSIS | DESCRIPTION | COMMAND LINE OPTIONS | FILESYSTEM INDEPENDENT MOUNT OPTIONS | FILESYSTEM SPECIFIC MOUNT OPTIONS | Mount options for adfs | Mount options for affs | Mount options for cifs | Mount options for coherent | Mount options for debugfs | Mount options for devpts | Mount options for ext | Mount options for ext2 | Mount options for ext3 | Mount options for ext4 | Mount options for fat | Mount options for hfs | Mount options for hpfs | Mount options for iso9660 | Mount options for jfs | Mount options for minix | Mount options for msdos | Mount options for ncpfs | Mount options for nfs and nfs4 | Mount options for ntfs | Mount options for proc | Mount options for ramfs | Mount options for reiserfs | Mount options for romfs | Mount options for squashfs | Mount options for smbfs | Mount options for sysv | Mount options for tmpfs | Mount options for ubifs | Mount options for udf | Mount options for ufs | Mount options for umsdos | Mount options for vfat | Mount options for usbfs | Mount options for xenix | Mount options for xfs | Mount options for xiafs | THE LOOP DEVICE | RETURN CODES | NOTES | FILES | ENVIRONMENT | SEE ALSO | BUGS | HISTORY | AUTHORS | AVAILABILITY

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