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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 the directory or	the 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 the --target or  --source
       options	to avoid ambivalent interpretation of the given	argument.  For

	      mount --target /mountpoint

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

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

	      The following command lists all  mounted	filesystems  (of  type

		     mount [-l]	[-t type]

	      The option -l adds labels	to this	listing.  See below.

       The device indication.
	      Most devices are indicated by a filename (of a block special de-
	      vice), like /dev/sda1, but there are other  possibilities.   For
	      example,	in  the	 case  of  an  NFS mount, device may look like  It is	also possible to indicate a block spe-
	      cial  device  using its filesystem label or UUID (see the	-L and
	      -U options below), or its	partition label	or  UUID.   (Partition
	      identifiers  are supported for example for GUID Partition	Tables

	      Don't forget that	there is no guarantee that  UUIDs  and	labels
	      are really unique, especially if you move, share or copy the de-
	      vice.  Use lsblk -o +UUID,PARTUUID to verify that	the UUIDs  are
	      really unique in your system.

	      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.  Tags are	more readable, robust and por-
	      table.  The mount(8) command internally uses udev	 symlinks,  so
	      the  use	of  symlinks in	/etc/fstab has no advantage over tags.
	      For more details see libblkid(3).

	      Note that	mount(8) uses UUIDs as strings.	 The  UUIDs  from  the
	      command  line or from fstab(5) are not converted to internal bi-
	      nary representation.  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	can be overridden with
	      the --fstab path command-line option (see	 below	for  more  de-

	      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	 specify  on the command line only the device, or only
	      the mount	point.

	      The programs mount and umount traditionally maintained  list  of
	      currently	 mounted  filesystems in the file /etc/mtab.  The mtab
	      file is still supported, but it's	recommended to use  a  symlink
	      to  the  file  /proc/mounts rather than the regular mtab file on
	      the  current  Linux  systems.   The  mtab	 file  maintained   in
	      userspace	 cannot	 reliably work with namespaces,	containers and
	      another advanced Linux features.

	      If no arguments are given	to mount, this list is printed.

	      If you want to override mount options from /etc/fstab  you  have
	      to use the -o option:

		     mount device|dir -o options

	      and  then	 the  mount  options from the command line will	be ap-
	      pended to	the list of options from /etc/fstab.  The usual	behav-
	      ior is that the last option wins if there	are conflicting	ones.

	      The  mount program does not read the /etc/fstab file if both de-
	      vice (or LABEL, UUID, PARTUUID or	PARTLABEL) and dir are	speci-
	      fied.  For example, to mount device foo at /dir:

		     mount /dev/foo /dir

       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	filesystem.

	      Thus, given a line

		     /dev/cdrom	 /cd  iso9660  ro,user,noauto,unhide

	      any  user	 can mount the iso9660 filesystem found	on an inserted
	      CDROM using 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 it, then use users instead of user in  the  fstab	 line.
	      The  owner  option  is  similar to the user option, with the re-
	      striction	that the user must be the owner	of the	special	 file.
	      This  may	be useful e.g. for /dev/fd if a	login script makes the
	      console user owner of this device.  The group option is similar,
	      with  the	 restriction that the user must	be member of the group
	      of the special file.

       The 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 by using this fstab entry:

		     /olddir /newdir none bind

	      After  this call the same	contents are 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
	      submounts	is attached a second place by using:

		     mount --rbind olddir newdir

	      Note that	the filesystem mount options will remain the  same  as
	      those  on	 the  original	mount  point, and cannot be changed by
	      passing the -o option along with --bind/--rbind.	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  the behavior of the remount operation	depends	on the
	      /etc/mtab	file.  The first command stores	the 'bind' flag	in 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
	      the  bind	flag (or option) for the remount command too.  For ex-

		     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 superblock will still
	      be writable, meaning 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

	      This will	cause the contents  which  previously  appeared	 under
	      olddir to	now be accessible under	newdir.	 The physical location
	      of the files is not changed.  Note  that	olddir	has  to	 be  a

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

       The shared subtree 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	the  ability to	create mirrors of that mount such that
	      mounts and unmounts within any of	the mirrors propagate  to  the
	      other  mirror.  A	slave mount receives propagation from its mas-
	      ter, but not vice	versa.	A private mount	carries	no propagation
	      abilities.   An unbindable mount is a private mount which	cannot
	      be cloned	through	a bind operation.  The detailed	semantics  are
	      documented  in  Documentation/filesystems/sharedsubtree.txt file
	      in the kernel source tree.

	      Supported	operations are:

		     mount --make-shared mountpoint
		     mount --make-slave	mountpoint
		     mount --make-private mountpoint
		     mount --make-unbindable mountpoint

	      The following commands allow 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 a --make-* operation	is re-
	      quested.	All necessary information has to be specified  on  the
	      command line.

	      Note  that  the  Linux  kernel does not allow to change multiple
	      propagation flags	with a single mount(2) syscall,	and the	 flags
	      cannot be	mixed with other mount options.

	      Since  util-linux	 2.23  the mount command allows	to use several
	      propagation flags	together and also together  with  other	 mount
	      operations.   This  feature  is  EXPERIMENTAL.   The propagation
	      flags are	applied	by additional mount(2) syscalls	when the  pre-
	      ceeding  mount  operations  were successful.  Note that this use
	      case is not atomic.  It is possible to specify  the  propagation
	      flags  in	fstab(5) as mount options (private, slave, shared, un-
	      bindable,	rprivate, rslave, rshared, runbindable).

	      For example:

		     mount --make-private --make-unbindable /dev/sda1 /foo

	      is the same as:

		     mount /dev/sda1 /foo
		     mount --make-private /foo
		     mount --make-unbindable /foo

       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.

       The  command  mount  does  not  pass  all  command-line	options	to the
       /sbin/mount.suffix mount	helpers.  The interface	between	mount and  the
       mount helpers is	described below	in the section EXTERNAL	HELPERS.

       Command-line options available for the mount command are:

       -V, --version
	      Display version information and exit.

       -h, --help
	      Display help text	and exit.

       -v, --verbose
	      Verbose mode.

       -a, --all
	      Mount  all  filesystems  (of the given types) mentioned in fstab
	      (except for those	whose line contains the	noauto keyword).   The
	      filesystems are mounted following	their order 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
	      disadvantage  is	that  the  mounts are done in undefined	order.
	      Thus, you	cannot use this	option if you want to mount both  /usr
	      and /usr/spool.

       -f, --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 an existing  record  in
	      /etc/mtab	and fails when the record already exists (with a regu-
	      lar non-fake mount, this check is	done by	the kernel).

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

       -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) by default.  This option  can
	      be  used together	with the -f flag for already canonicalized ab-
	      solute paths.  The option	is designed for	 mount	helpers	 which
	      call  mount -i.  It is strongly recommended to not use this com-
	      mand-line	option for normal mount	operations.

	      Note  that  mount(8)  does  not  pass   this   option   to   the
	      /sbin/mount.type helpers.

       -s     Tolerate	sloppy	mount  options rather than failing.  This will
	      ignore mount options not supported by a  filesystem  type.   Not
	      all  filesystems	support	this option.  Currently	it's supported
	      by the mount.nfs mount helper only.

       --source	dev
	      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  ar-
	      gument is	the mount source.

       --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 ar-
	      gument is	the mount target.

       -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 exam-
	      ple, ext3	and ext4 will replay the journal if the	filesystem  is
	      dirty.   To  prevent  this kind of write access, you may want to
	      mount an ext3 or ext4 filesystem with the	 ro,noload  mount  op-
	      tions  or	set the	block device itself to read-only mode, see the
	      blockdev(8) command.

       -w, --rw, --read-write
	      Mount the	filesystem read/write.	This is	the default.   A  syn-
	      onym 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	 an  alternative  fstab	 file.	If path	is a directory
	      then the files in	the directory  are  sorted  by	strverscmp(3);
	      files that start with "."	or without an .fstab extension are ig-
	      nored.  The option can be	specified more than once.  This	option
	      is  mostly  designed for initramfs or chroot scripts where addi-
	      tional configuration is specified	beyond standard	system config-

	      Note  that  mount(8)  does  not  pass  the option	--fstab	to the
	      /sbin/mount.type helpers,	meaning	 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	the 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, btrfs, cifs, coda, coherent, cramfs,
	      debugfs, 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	a  '.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 deprecated).

	      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) an 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  different  ver-
	      sions  of	 the  smbmount	program	have different calling conven-
	      tions, /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 *,  mount  will
	      read /proc/filesystems afterwards.  While	trying,	all filesystem
	      types will be mounted with the 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.

       -O, --test-opts opts
	      Limit the	set of filesystems to which the	-a option applies.  In
	      this  regard  it is like the -t option except that -O is useless
	      without -a.  For example,	the command:

		     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
	      Use the specified	mount options.	The opts argument is a	comma-
	      separated	list.  For example:

		     mount LABEL=mydisk	-o noatime,nodev,nosuid

	      For  more	 details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS

       -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
       /proc/mounts.   Note that filesystems also have per-filesystem specific
       default mount options (see for  example	tune2fs	 -l  output  for  extN

       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 an 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 the noatime feature, so the inode access time is con-
	      trolled  by  kernel  defaults.  See also the descriptions	of the
	      strictatime 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 ver-
	      sions.  Even where xattrs	are supported, you can save  time  not
	      having  to label every file by assigning the entire disk one se-
	      curity context.

	      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  filesys-
	      tem  label  is separate from the individual labels on the	files.
	      It represents the	entire filesystem for certain kinds of permis-
	      sion  checks, such as during mount or file creation.  Individual
	      file labels are still obtained from  the	xattrs	on  the	 files
	      themselves.  The context option actually sets the	aggregate con-
	      text 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 \

	      For more details,	see selinux(8).

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

	      Note that	the real set of	all default mount options  depends  on
	      kernel  and  filesystem type.  See the beginning of this section
	      for more details.

       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 permit 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 it 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 the relatime feature.	See also the strictatime mount

	      Allows  to explicitly request full atime updates.	 This makes it
	      possible for the kernel to default 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 behavior	for inode access time updates.

       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.

       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  the	 mount
	      command  works  with  options  from  fstab.  This	means that the
	      mount command only doesn't read fstab (or	mtab)  when  both  the
	      device and dir are 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 the options from the 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  the
	      case  of	media with a 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 (or to the private libmount
	      file in /run/mount on system without regular mtab)  so  that  he
	      can  unmount  the	filesystem again.  This	option implies the op-
	      tions noexec, nosuid, 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; it does not imply any other options.

       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	application-specific options.  These options  are  not
	      stored  in  the  mtab file, nor sent to the mount.<type> helpers
	      nor the mount(2) system call.  The suggested format  is  x-<app-
	      name>.<option> (e.g. x-systemd.automount).

	      Allow to make a target directory (mountpoint).  The optional ar-
	      gument mode  specifies  the  filesystem  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 btrfs
       Btrfs is	a copy-on-write	filesystem for Linux aimed at implementing ad-
       vanced features while focusing on fault tolerance, repair, and easy ad-

	      Debugging	 option	to force all block allocations above a certain
	      byte threshold on	each block device.  The	value is specified  in
	      bytes,  optionally  with	a K, M,	or G suffix, case insensitive.
	      Default is 1MB.

	      Disable/enable auto defragmentation.  Auto  defragmentation  de-
	      tects  small random writes into files and	queues them up for the
	      defrag process.  Works best for small files; not well-suited for
	      large database workloads.

	      These  debugging	options	 control the behavior of the integrity
	      checking module(the BTRFS_FS_CHECK_INTEGRITY config  option  re-

	      check_int	 enables  the integrity	checker	module,	which examines
	      all block-write requests to ensure  on-disk  consistency,	 at  a
	      large memory and CPU cost.

	      check_int_data includes extent data in the integrity checks, and
	      implies the check_int option.

	      check_int_print_mask takes  a  bitmask  of  BTRFSIC_PRINT_MASK_*
	      values  as defined in fs/btrfs/check-integrity.c,	to control the
	      integrity	checker	module behavior.

	      See comments at the top of fs/btrfs/check-integrity.c  for  more

	      Set  the	interval  of  periodic	commit,	30 seconds by default.
	      Higher values defer data being synced to permanent storage, with
	      obvious  consequences  when the system crashes.  The upper bound
	      is not forced, but a warning is printed if it's  more  than  300
	      seconds (5 minutes).

	      Control  BTRFS  file data	compression.  Type may be specified as
	      "zlib" "lzo" or "no" (for	no compression,	used for  remounting).
	      If  no  type  is	specified, zlib	is used.  If compress-force is
	      specified, all files will	be compressed,	whether	 or  not  they
	      compress well.  If compression is	enabled, nodatacow and nodata-
	      sum are disabled.

	      Allow mounts to continue with  missing  devices.	 A  read-write
	      mount  may  fail with too	many devices missing, for example if a
	      stripe member is completely missing.

	      Specify a	device during mount so that ioctls on the control  de-
	      vice  can	 be avoided.  Especially useful	when trying to mount a
	      multi-device setup as root.  May be specified multiple times for
	      multiple devices.

	      Disable/enable  the  discard mount option.  The discard function
	      issues frequent 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 sig-
	      nificant performance impact.  (The fstrim	command	is also	avail-
	      able to initiate batch trims from	userspace.)

	      Disable/enable debugging option  to  be  more  verbose  in  some
	      ENOSPC conditions.

	      Action to	take when encountering a fatal error:
		"bug" -	BUG() on a fatal error.	 This is the default.
		"panic"	- panic() on a fatal error.

	      The  flushoncommit  mount	 option	 forces	 any data dirtied by a
	      write in a prior transaction to commit as	part  of  the  current
	      commit.	This makes the committed state a fully consistent view
	      of the filesystem	from the application's perspective  (i.e.,  it
	      includes	all completed filesystem operations).  This was	previ-
	      ously the	behavior only when a snapshot is created.

	      Enable free inode	number caching.	  Defaults to off  due	to  an
	      overflow	problem	 when  the  free space CRCs don't fit inside a
	      single page.

	      Specify the maximum amount of space, in bytes, that can  be  in-
	      lined  in	 a  metadata  B-tree  leaf.  The value is specified in
	      bytes, optionally	with a K, M, or	G  suffix,  case  insensitive.
	      In practice, this	value is limited by the	root sector size, with
	      some space unavailable due to leaf headers.  For	a  4k  sector-
	      size, max	inline data is ~3900 bytes.

	      Specify  that  1	metadata chunk should be allocated after every
	      value data chunks.  Off by default.

       noacl  Enable/disable support for Posix Access  Control	Lists  (ACLs).
	      See the acl(5) manual page for more information about ACLs.

	      Enable/disable  the  use	of  block-layer	write barriers.	 Write
	      barriers ensure that certain IOs	make  it  through  the	device
	      cache  and  are  on persistent storage.  If disabled on a	device
	      with a volatile (non-battery-backed) write-back cache,  the  no-
	      barrier  option  will  lead to filesystem	corruption on a	system
	      crash or power loss.

	      Enable/disable data copy-on-write	for newly created files.  This
	      option implies nodatasum,	and disables all compression.

	      Enable/disable  data checksumming	for newly created files.  This
	      option implies datacow.

	      Enable/disable the  tree	logging	 used  for  fsync  and	O_SYNC

	      Enable  autorecovery  attempts  if  a  bad tree root is found at
	      mount time.  Currently this scans	a  list	 of  several  previous
	      tree roots and tries to use the first readable.

	      Force check and rebuild procedure	of the UUID tree.  This	should
	      not normally be needed.

	      Skip automatic resume of an interrupted balance operation	 after
	      mount.  May be resumed with "btrfs balance resume."

	      Disable freespace	cache loading without clearing the cache.

	      Force  clearing  and rebuilding of the disk space	cache if some-
	      thing has	gone wrong.

	      Options to control ssd allocation	schemes.   By  default,	 BTRFS
	      will  enable  or	disable	ssd allocation heuristics depending on
	      whether a	rotational or nonrotational disk is in use.   The  ssd
	      and nossd	options	can override this autodetection.

	      The ssd_spread mount option attempts to allocate into big	chunks
	      of unused	 space,	 and  may  perform  better  on	low-end	 ssds.
	      ssd_spread  implies  ssd,	 enabling  all other ssd heuristics as

	      Mount subvolume at path rather than  the	root  subvolume.   The
	      path is relative to the top level	subvolume.

	      Mount  subvolume	specified by an	ID number rather than the root
	      subvolume.  This allows mounting of subvolumes which are not  in
	      the  root	of the mounted filesystem.  You	can use	"btrfs subvol-
	      ume list"	to see subvolume ID numbers.

       subvolrootid=objectid  (deprecated)
	      Mount subvolume specified	by objectid rather than	the root  sub-
	      volume.  This allows mounting of subvolumes which	are not	in the
	      root of the mounted filesystem.  You can	use  "btrfs  subvolume
	      show " to	see the	object ID for a	subvolume.

	      The number of worker threads to allocate.	 The default number is
	      equal to the number of CPUs + 2, or 8, whichever is smaller.

	      Allow subvolumes to be deleted by	a  non-root  user.   Use  with

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  CON-
	      FIG_DEVPTS_MULTIPLE_INSTANCES  is	enabled	in the kernel configu-

	      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 CON-
	      FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel  configu-

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

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 behavior for the statfs system call.  The	minixdf	behav-
	      ior is to	return in the  f_blocks	 field	the  total  number  of
	      blocks of	the filesystem,	while the bsddf	behavior (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  behavior 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  man-
	      age 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 1 k
	      units.  Thus, if you want	 to  use  logical  block  32768	 on  a
	      filesystem with 4	k 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 jour-
	      nal, overwriting the old contents	of the file whose inode	number
	      is inum.

	      When  the	 external  journal  device's  major/minor numbers have
	      changed, these options allow the user to specify the new journal
	      location.	  The  journal device is identified either through its
	      new major/minor numbers encoded in devnum, or via	a path to  the

	      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.

	      Just  print  an  error message if	an error occurs	in a file data
	      buffer in	ordered	mode.

	      Abort the	journal	if an error occurs in a	file  data  buffer  in
	      ordered mode.

       barrier=0 / barrier=1
	      This  disables  /	 enables  the use of write barriers in the jbd
	      code.  barrier=0 disables, barrier=1  enables  (default).	  This
	      also requires an IO stack	which can support barriers, and	if jbd
	      gets an error on a barrier write,	it will	disable	barriers again
	      with  a warning.	Write barriers enforce proper on-disk ordering
	      of journal commits, making volatile disk write  caches  safe  to
	      use,  at	some  performance penalty.  If your disks are battery-
	      backed in	one way	or another, disabling barriers may safely  im-
	      prove performance.

	      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
	      quotas   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	advan-
	      tage 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,  norecovery,  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,	 grpquota, usrquota usrjquota, grpjquota and jqfmt are
       backwardly compatible 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
	      These  mount options have	the same effect	as in ext3.  The mount
	      options "barrier"	and "nobarrier"	are added 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
	      operations will join the transaction.  The commit	time is	capped
	      by the max_batch_time, which defaults to 15000 <micro>s (15 ms).
	      This   optimization  can	be  turned  off	 entirely  by  setting
	      max_batch_time to	0.

	      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.

	      Do  not  initialize  any uninitialized inode table blocks	in the
	      background.  This	feature	may be used by	installation  CD's  so
	      that  the	 install  process can complete as quickly as possible;
	      the inode	table initialization process would  then  be  deferred
	      until the	next time the filesystem is mounted.

	      The  lazy	 itable	init code will wait n times the	number of mil-
	      liseconds	it took	to zero	out the	previous block	group's	 inode
	      table.   This  minimizes	the impact on system performance while
	      the filesystem's inode table is being initialized.

	      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.

	      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
	      uninitialized 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 jour-
	      naling 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).

	      This  limits  the	size of	the directories	so that	any attempt to
	      expand them beyond the specified limit in	kilobytes  will	 cause
	      an  ENOSPC error.	 This is useful	in memory-constrained environ-
	      ments, where a very large	directory can cause severe performance
	      problems or even provoke the Out Of Memory killer. (For example,
	      if there is only 512 MB memory available,	a 176 MB directory may
	      seriously	cramp the system's style.)

	      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	pickiness 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 that contain long parts or spe-
		     cial characters that are sometimes	used on	Linux but  are
		     not accepted by MS-DOS (+,	=, etc.) are rejected.

	      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  conversion  (MS-DOS
	      text  format  to UNIX text format) in the	kernel.	 The following
	      conversion modes are available:

		     No	translation is performed.  This	is the default.

	      t[ext] CRLF<-->NL	translation is performed on all	files.

	      a[uto] 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
	      filenames	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. map.

	      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 and execute  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 16 MB.

	      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
	      remount, when the	volume is mounted read-write.  The resize key-
	      word with	no value will grow the volume to the full size of  the

	      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 behavior 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

	      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
		     default  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  im-
	      provements in some situations.

	      Tunes  the  block	 allocator.   This may provide performance im-
	      provements 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 disables / enables the use of write barriers	in  the	 jour-
	      naling  code.  barrier=none disables, barrier=flush enables (de-
	      fault).  This also requires an IO	stack which can	support	barri-
	      ers,  and	 if reiserfs gets an error on a	barrier	write, it will
	      disable barriers again with a warning.  Write  barriers  enforce
	      proper on-disk ordering of journal commits, making volatile disk
	      write caches safe	to use,	at some	performance penalty.  If  your
	      disks are	battery-backed in one way or another, disabling	barri-
	      ers may safely improve performance.

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) ac-
       cept a suffix k,	m or g for Ki, Mi, Gi (binary kilo (kibi), binary mega
       (mebi) and binary giga (gibi)) 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-minus"-separated  decimal
	      numbers,	the  smallest  and  largest node numbers in the	range.
	      For example, 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  (NetBSD,
		     FreeBSD, OpenBSD).

	      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 behavior 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 invalid on the vfat filesystem.
	      The escape sequence that gets used, where	u is the Unicode char-
	      acter, 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 behavior for creation	and display of filenames which
	      fit  into	 8.3 characters.  If a long name for a file exists, it
	      will always be the preferred one for display.   There  are  four

	      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 short	name 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 behavior 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
	      allocsize	value turns off	the dynamic behavior.

	      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  behavior  is determined by the on-disk feature bit
	      indicating that attr2 behavior 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 clus-
	      ters and keeps them around on disk.  When	noikeep	is  specified,
	      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"	speci-
	      fied but does specify an "allocsize" then	"allocsize" (in	bytes)
	      will be returned instead.	 Otherwise the behavior	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 con-
	      trols the	size of	each buffer and	so is also  relevant  to  this

	      Set  the	size  of  each	in-memory log buffer.  The size	may be
	      specified	in bytes, or in	kibibytes (KiB)	 with  a  "k"  suffix.
	      Valid  sizes  for	 version  1  and  version  2  logs  are	 16384
	      (value=16k) and 32768 (value=32k).  Valid	sizes  for  version  2
	      logs  also  include  65536  (value=64k), 131072 (value=128k) and
	      262144 (value=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).

       logdev=device and rtdev=device
	      Use an external log (metadata journal) and/or real-time  device.
	      An  XFS  filesystem has up to three parts: a data	section, a log
	      section, and a real-time section.	 The real-time section is  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	 inte-
	      ger 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.

       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/loop3

       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 three 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 auto-destruction of loop devices is supported, mean-
       ing that	any loop device	allocated by mount will	be freed by umount in-
       dependently of /etc/mtab.

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

       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 succeeded), 32 (all failed),	or  64
       (some failed, some succeeded).

       The syntax of external mount helpers is:

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

       where the suffix	is the filesystem type and the -sfnvo options have the
       same  meaning  as  the normal mount options.  The -t option is used for
       filesystems with	subtypes  support  (for	 example  /sbin/mount.fuse  -t

       The  command mount does not pass	the mount options unbindable, runbind-
       able, private, rprivate,	slave, rslave, shared, rshared,	auto,  noauto,
       comment,	x-*, loop, offset and sizelimit	to the mount.<suffix> helpers.
       All other options are used in a comma-separated list as argument	to the
       -o option.

       /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 on
       systems with regular mtab file. 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 particu-
       lar  case  the mount command may	reports	unreliable information about a
       NFS mount point and the /proc/mounts file usually contains  more	 reli-
       able  information.)  This  is  another reason to	replace	mtab file with
       symlink to the /proc/mounts file.

       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			   July	2014			      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 btrfs | 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 | THE LOOP DEVICE | RETURN CODES | EXTERNAL HELPERS | FILES | ENVIRONMENT | SEE ALSO | BUGS | HISTORY | AUTHORS | AVAILABILITY

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