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MOUNT(8)		     System Administration		      MOUNT(8)

NAME
       mount - mount a filesystem

SYNOPSIS
       mount [-lhV]

       mount -a	[-fFnrsvw] [-t vfstype]	[-O optlist]

       mount [-fnrsvw] [-o option[,option]...]	device|dir

       mount [-fnrsvw] [-t vfstype] [-o	options] device	dir

DESCRIPTION
       All files accessible in a Unix system are arranged in one big tree, the
       file hierarchy, rooted at /.  These files can be	spread out  over  sev-
       eral  devices.  The mount command serves	to attach the filesystem found
       on some device to the big file tree. Conversely,	the umount(8)  command
       will detach it again.

       The standard form of the	mount command, is

	      mount -t type device dir

       This  tells  the	kernel to attach the filesystem	found on device	(which
       is of type type)	at the directory dir.  The previous contents (if  any)
       and  owner  and	mode  of  dir  become  invisible,  and as long as this
       filesystem remains mounted, the pathname	dir refers to the root of  the
       filesystem on device.

       If only directory or device is given, for example:

	      mount /dir

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

	      mount --target /mountpoint

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

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

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

       The device indication.
	      Most  devices  are  indicated by a file name (of a block special
	      device), like /dev/sda1, but there are other possibilities.  For
	      example,	in  the	 case  of  an  NFS mount, device may look like
	      knuth.cwi.nl:/dir.  It is	possible to indicate a	block  special
	      device  using  its  filesystem  LABEL or UUID (see the -L	and -U
	      options below) and partition PARTUUID  or	 PARTLABEL  (partition
	      identifiers are supported	for GUID Partition Table (GPT) and MAC
	      partition	tables only).

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

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

	      The proc filesystem is not associated with a special device, and
	      when mounting it,	an arbitrary keyword, such as proc can be used
	      instead of a device specification.  (The customary  choice  none
	      is less fortunate: the error message `none busy' from umount can
	      be confusing.)

       The /etc/fstab, /etc/mtab and /proc/mounts files.
	      The file /etc/fstab (see fstab(5)), may contain lines describing
	      what devices are usually mounted where, using which options. The
	      default location of the fstab(5) file  could  be	overridden  by
	      --fstab <path> command line option (see below for	more details).

	      The command

		     mount -a [-t type]	[-O optlist]

	      (usually given in	a bootscript) causes all filesystems mentioned
	      in  fstab	 (of  the  proper type and/or having or	not having the
	      proper options) to be mounted as	indicated,  except  for	 those
	      whose  line  contains  the  noauto keyword. Adding the -F	option
	      will make	mount fork, so that the	filesystems are	mounted	simul-
	      taneously.

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

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

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

		     mount /dev/foo /dir

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

		     mount device|dir -o <options>

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

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

       The non-superuser mounts.
	      Normally,	 only  the  superuser can mount	filesystems.  However,
	      when fstab contains the user option on a line, anybody can mount
	      the corresponding	system.

	      Thus, given a line

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

	      any  user	 can  mount  the iso9660 filesystem found on his CDROM
	      using the	command

		     mount /dev/cdrom

	      or

		     mount /cd

	      For more details,	see fstab(5).  Only the	user  that  mounted  a
	      filesystem  can unmount it again.	 If any	user should be able to
	      unmount, then use	users instead of user in the fstab line.   The
	      owner option is similar to the user option, with the restriction
	      that the user must be the	owner of the special file. This	may be
	      useful e.g. for /dev/fd if a login script	makes the console user
	      owner of this device.  The group option  is  similar,  with  the
	      restriction  that	 the  user  must be member of the group	of the
	      special file.

       The bind	mounts.
	      Since Linux 2.4.0	it is possible to remount  part	 of  the  file
	      hierarchy	somewhere else.	The call is
		     mount --bind olddir newdir
	      or shortoption
		     mount -B olddir newdir
	      or fstab entry is:
		     /olddir /newdir none bind

	      After  this  call	the same contents is accessible	in two places.
	      One can also remount a single file (on a single file). It's also
	      possible	to  use	 the  bind mount to create a mountpoint	from a
	      regular directory, for example:

		     mount --bind foo foo

	      The bind mount call attaches only	(part of) a single filesystem,
	      not possible submounts. The entire file hierarchy	including sub-
	      mounts is	attached a second place	using

		     mount --rbind olddir newdir

	      or shortoption

		     mount -R olddir newdir

	      Note that	the filesystem mount options will remain the  same  as
	      those  on	 the  original	mount  point, and cannot be changed by
	      passing the -o  option  along  with  --bind/--rbind.  The	 mount
	      options  can be changed by a separate remount command, for exam-
	      ple:

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

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

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

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

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

	      Note  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 subtrees operations.
	      Since  Linux  2.6.15 it is possible to mark a mount and its sub-
	      mounts as	shared,	private, slave or unbindable. A	 shared	 mount
	      provides	ability	 to  create  mirrors  of  that mount such that
	      mounts and umounts within	any of the mirrors  propagate  to  the
	      other  mirror.  A	slave mount receives propagation from its mas-
	      ter, but any not vice-versa.  A private mount carries no	propa-
	      gation  abilities.   A unbindable	mount is a private mount which
	      cannot be	cloned through a bind operation. Detailed semantics is
	      documented  in  Documentation/filesystems/sharedsubtree.txt file
	      in the kernel source tree.

	      Supported	operations:
		     mount --make-shared mountpoint
		     mount --make-slave	mountpoint
		     mount --make-private mountpoint
		     mount --make-unbindable mountpoint

	      The following commands allows one	to recursively change the type
	      of all the mounts	under a	given mountpoint.

		     mount --make-rshared mountpoint
		     mount --make-rslave mountpoint
		     mount --make-rprivate mountpoint
		     mount --make-runbindable mountpoint

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

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

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

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

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

COMMAND	LINE OPTIONS
       The full	set of mount options used by an	invocation of mount is	deter-
       mined by	first extracting the mount options for the filesystem from the
       fstab table, then applying any options specified	by  the	 -o  argument,
       and finally applying a -r or -w option, when present.

       Command line options available for the mount command:

       -V, --version
	      Output version.

       -h, --help
	      Print a help message.

       -v, --verbose
	      Verbose mode.

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

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

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

       -i, --internal-only
	      Don't  call  the	/sbin/mount.<filesystem>  helper  even	if  it
	      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
	      e2label(8) utility, or for XFS using xfs_admin(8), or for	 reis-
	      erfs using reiserfstune(8).

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

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

       -s     Tolerate	sloppy	mount  options	rather than failing. This will
	      ignore mount options not supported by a filesystem type. Not all
	      filesystems  support this	option.	This option exists for support
	      of the Linux autofs-based	automounter.

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

       -r, --read-only
	      Mount the	filesystem read-only. A	synonym	is -o ro.

	      Note  that,  depending  on the filesystem	type, state and	kernel
	      behavior,	the system may still write to the device. For example,
	      Ext3 or ext4 will	replay its journal if the filesystem is	dirty.
	      To prevent this kind of write access, you	may want to mount ext3
	      or  ext4	filesystem  with  "ro,noload" mount options or set the
	      block device to read-only	mode, see command blockdev(8).

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

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

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

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

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

       -t, --types vfstype
	      The argument following the -t is used to indicate	the filesystem
	      type.   The  filesystem  types  which  are  currently  supported
	      include:	adfs,  affs,  autofs,  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
	      coherent,	sysv and xenix	are  equivalent	 and  that  xenix  and
	      coherent will be removed at some point in	the future -- use sysv
	      instead. Since kernel version 2.1.21 the types ext and xiafs  do
	      not  exist anymore. Earlier, usbfs was known as usbdevfs.	 Note,
	      the real list of all supported filesystems depends on your  ker-
	      nel.

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

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

	      If  no  -t  option  is  given, or	if the auto type is specified,
	      mount will try to	guess the desired type.	 Mount uses the	 blkid
	      library  for guessing the	filesystem type; if that does not turn
	      up anything that looks familiar, mount will try to read the file
	      /etc/filesystems,	or, if that does not exist, /proc/filesystems.
	      All of the filesystem types listed there will be	tried,	except
	      for those	that are labeled "nodev" (e.g.,	devpts,	proc and nfs).
	      If /etc/filesystems ends in a line with a	single *  only,	 mount
	      will  read  /proc/filesystems  afterwards. All of	the filesystem
	      types will be mounted with mount option "silent".

	      The auto type may	be useful for user-mounted floppies.  Creating
	      a	 file /etc/filesystems can be useful to	change the probe order
	      (e.g., to	try vfat before	msdos or ext3 before ext2) or  if  you
	      use a kernel module autoloader.

	      More  than  one type may be specified in a comma separated list.
	      The list of filesystem types can be prefixed with	no to  specify
	      the  filesystem types on which no	action should be taken.	 (This
	      can be meaningful	with the -a option.) For example, the command:

		     mount -a -t nomsdos,ext

	      mounts all filesystems except those of type msdos	and ext.

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

       -O, --test-opts opts
	      Used in conjunction with -a, to limit the	set of filesystems  to
	      which  the -a is applied.	 Like -t in this regard	except that it
	      is useless except	in the context of -a.  For example,  the  com-
	      mand:

		     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
	      rest.

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

		     mount -a -t ext2 -O _netdev

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

       -o, --options opts
	      Options  are  specified with a -o	flag followed by a comma sepa-
	      rated string of options. For example:

		     mount LABEL=mydisk	-o noatime,nouser

	      For more details,	see FILESYSTEM INDEPENDENT MOUNT  OPTIONS  and
	      FILESYSTEM SPECIFIC MOUNT	OPTIONS	sections.

       -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.

FILESYSTEM INDEPENDENT MOUNT OPTIONS
       Some  of	 these	options	 are  only  useful  when  they	appear	in the
       /etc/fstab file.

       Some of these options could be enabled or disabled by  default  in  the
       system  kernel.	To  check  the	current	 setting  see  the  options in
       /proc/mounts.

       The following options apply to any filesystem  that  is	being  mounted
       (but  not every filesystem actually honors them - e.g., the sync	option
       today has effect	only for ext2, ext3, fat, vfat and ufs):

       async  All I/O to the filesystem	should be  done	 asynchronously.  (See
	      also the sync option.)

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

       noatime
	      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-
       text=context
	      The  context= option is useful when mounting filesystems that do
	      not support extended attributes, such as a floppy	or  hard  disk
	      formatted	 with  VFAT,  or systems that are not normally running
	      under SELinux, such as an	ext3 formatted disk from a non-SELinux
	      workstation. You can also	use context= on	filesystems you	do not
	      trust, such as a floppy. It also	helps  in  compatibility  with
	      xattr-supporting filesystems on earlier 2.4.<x> kernel versions.
	      Even where xattrs	are supported, you can save time not having to
	      label  every file	by assigning the entire	disk one security con-
	      text.

	      A	commonly used option  for  removable  media  is	 context="sys-
	      tem_u:object_r:removable_t".

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

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

	      You  can	set  the  default security context for unlabeled files
	      using 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-
	      text.

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

		     mount    -t    tmpfs    none   /mnt   -o	'context="sys-
		     tem_u:object_r:tmp_t:s0:c127,c456",noexec'

	      For more details,	see selinux(8).

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

       dev    Interpret	 character or block special devices on the filesystem.

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

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

       nodiratime
	      Do not update directory inode access times on this filesystem.

       dirsync
	      All directory updates within the filesystem should be done  syn-
	      chronously.   This  affects  the	following system calls:	creat,
	      link, unlink, symlink, mkdir, rmdir, mknod and rename.

       exec   Permit execution of binaries.

       noexec Do not allow direct execution of any  binaries  on  the  mounted
	      filesystem.   (Until  recently  it  was possible to run binaries
	      anyway using a command like /lib/ld*.so /mnt/binary. This	 trick
	      fails since Linux	2.4.25 / 2.6.0.)

       group  Allow  an	ordinary (i.e.,	non-root) user to mount	the filesystem
	      if one of	his groups matches the	group  of  the	device.	  This
	      option  implies  the options nosuid and nodev (unless overridden
	      by subsequent options, as	in the option line group,dev,suid).

       iversion
	      Every time the inode is modified,	the i_version  field  will  be
	      incremented.

       noiversion
	      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.

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

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

       relatime
	      Update  inode  access  times  relative to	modify or change time.
	      Access time is only updated if the previous access time was ear-
	      lier  than  the current modify or	change time. (Similar to noat-
	      ime, but doesn't break mutt or other applications	that  need  to
	      know  if	a  file	has been read since the	last time it was modi-
	      fied.)

	      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
	      addition,	 since	Linux  2.6.30,	the file's last	access time is
	      always  updated  if  it  is more than 1 day old.

       norelatime
	      Do not use relatime feature.  See	 also  the  strictatime	 mount
	      option.

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

       nostrictatime
	      Use  the	kernel's  default  behaviour  for  inode  access  time
	      updates.

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

       nosuid Do not allow set-user-identifier or set-group-identifier bits to
	      take  effect.  (This seems safe, but is in fact rather unsafe if
	      you have suidperl(1) installed.)

       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
	      options  nosuid  and  nodev  (unless  overridden	by  subsequent
	      options, as in the option	line owner,dev,suid).

       remount
	      Attempt  to remount an already-mounted filesystem.  This is com-
	      monly used to change the mount flags  for	 a  filesystem,	 espe-
	      cially  to  make	a  readonly  filesystem	 writable. It does not
	      change device or mount point.

	      The remount functionality	follows	the standard way how the mount
	      command  works  with options from	fstab. It means	the mount com-
	      mand doesn't read	fstab (or mtab)	only when a device and dir are
	      fully specified.

	      mount -o remount,rw /dev/foo /dir

	      After this call all old mount options are	replaced and arbitrary
	      stuff from fstab is ignored, except the loop=  option  which  is
	      internally generated and maintained by the mount command.

	      mount -o remount,rw  /dir

	      After  this  call	 mount	reads fstab (or	mtab) and merges these
	      options with options from	command	line ( -o ).

       ro     Mount the	filesystem read-only.

       rw     Mount the	filesystem read-write.

       sync   All I/O to the filesystem	should be done synchronously. In  case
	      of  media	 with  limited number of write cycles (e.g. some flash
	      drives) "sync" may cause life-cycle shortening.

       user   Allow an ordinary	user to	mount the filesystem.  The name	of the
	      mounting	user  is  written  to  mtab so that he can unmount the
	      filesystem again.	  This	option	implies	 the  options  noexec,
	      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.

       users  Allow  every  user  to  mount  and unmount the filesystem.  This
	      option implies the options noexec,  nosuid,  and	nodev  (unless
	      overridden   by  subsequent  options,  as	 in  the  option  line
	      users,exec,dev,suid).

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

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

FILESYSTEM SPECIFIC MOUNT OPTIONS
       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-
       tion/filesystems.

Mount options for adfs
       uid=value and gid=value
	      Set the owner and	group of the files in the filesystem (default:
	      uid=gid=0).

       ownmask=value and othmask=value
	      Set the permission mask for ADFS 'owner' permissions and 'other'
	      permissions,  respectively  (default:  0700  and	0077,  respec-
	      tively).	   See	  also	 /usr/src/linux/Documentation/filesys-
	      tems/adfs.txt.

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

       mode=value
	      Set the mode of all files	to value & 0777	disregarding the orig-
	      inal  permissions.   Add	search	permission to directories that
	      have read	permission.  The value is given	in octal.

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

       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...

       verbose
	      Print an informational message for each successful mount.

       prefix=string
	      Prefix used before volume	name, when following a link.

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

       reserved=value
	      (Default:	2.) Number of  unused  blocks  at  the	start  of  the
	      device.

       root=value
	      Give explicitly the location of the root block.

       bs=value
	      Give blocksize. Allowed values are 512, 1024, 2048, 4096.

       grpquota|noquota|quota|usrquota
	      These  options are accepted but ignored.	(However, quota	utili-
	      ties may react to	such strings in	/etc/fstab.)

Mount options for cifs
       See the options section of the mount.cifs(8) man	page (cifs-utils pack-
       age must	be installed).

Mount options for coherent
       None.

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
       options:

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

       mode=value
	      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
       /dev/pts/<number>.

       uid=value and gid=value
	      This  sets  the  owner or	the group of newly created PTYs	to the
	      specified	values.	When nothing is	specified, they	will be	set to
	      the  UID and GID of the creating process.	 For example, if there
	      is a tty group with GID 5, then gid=5 will cause	newly  created
	      PTYs to belong to	the tty	group.

       mode=value
	      Set  the mode of newly created PTYs to the specified value.  The
	      default is 0600.	A value	of mode=620 and	gid=5 makes  "mesg  y"
	      the default on newly created PTYs.

       newinstance
	      Create  a	 private  instance  of	devpts	filesystem,  such that
	      indices 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-
	      ration.

	      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.

       ptmxmode=value

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

	      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-
	      ration.

Mount options for ext
       None.  Note that	the `ext' filesystem is	obsolete. Don't	use it.	 Since
       Linux version 2.1.21 extfs is no	longer part of the kernel source.

Mount options for ext2
       The  `ext2'  filesystem	is the standard	Linux filesystem.  Since Linux
       2.5.46, for most	 mount	options	 the  default  is  determined  by  the
       filesystem superblock. Set them with tune2fs(8).

       acl|noacl
	      Support POSIX Access Control Lists (or not).

       bsddf|minixdf
	      Set the behaviour	for the	statfs system call. The	minixdf	behav-
	      iour is to return	in the f_blocks	 field	the  total  number  of
	      blocks  of  the  filesystem, while the bsddf behaviour (which is
	      the default) is to subtract the overhead blocks used by the ext2
	      filesystem and not available for file storage. Thus

	      %	mount /k -o minixdf; df	/k; umount /k
	      Filesystem   1024-blocks	Used Available Capacity	Mounted	on
	      /dev/sda6	     2630655   86954  2412169	   3%	/k
	      %	mount /k -o bsddf; df /k; umount /k
	      Filesystem   1024-blocks	Used Available Capacity	Mounted	on
	      /dev/sda6	     2543714	  13  2412169	   0%	/k

	      (Note  that  this	 example  shows	 that one can add command line
	      options 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.

       errors={continue|remount-ro|panic}
	      Define  the  behaviour  when  an	error is encountered.  (Either
	      ignore errors and	just mark the filesystem  erroneous  and  con-
	      tinue,  or  remount  the filesystem read-only, or	panic and halt
	      the system.)  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.

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

       nouid32
	      Disables	32-bit	UIDs  and  GIDs.  This is for interoperability
	      with older kernels which only store and expect 16-bit values.

       oldalloc	or orlov
	      Use old allocator	or Orlov allocator for new  inodes.  Orlov  is
	      default.

       resgid=n	and resuid=n
	      The  ext2	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
	      group.)

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

       user_xattr|nouser_xattr
	      Support "user." extended attributes (or not).

Mount options for ext3
       The  ext3 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:

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

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

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

       norecovery/noload
	      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.

       data={journal|ordered|writeback}
	      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-
	      flags=data=journal.

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

	      ordered
		     This  is  the  default mode.  All data is forced directly
		     out to the	main file system prior to its  metadata	 being
		     committed to the journal.

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

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

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

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

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

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

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

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

       journal_checksum
	      Enable checksumming of  the  journal  transactions.   This  will
	      allow  the recovery code in e2fsck and the kernel	to detect cor-
	      ruption in the kernel.  It is a compatible change	 and  will  be
	      ignored by older kernels.

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

       barrier=0 / barrier=1 / barrier / nobarrier
	      This enables/disables the	use of write barriers in the jbd code.
	      barrier=0	disables, barrier=1 enables.  This also	requires an IO
	      stack  which can support barriers, and if	jbd gets an error on a
	      barrier write, it	will disable again with	a warning.  Write bar-
	      riers enforce proper on-disk ordering of journal commits,	making
	      volatile disk write caches safe  to  use,	 at  some  performance
	      penalty.	 If  your  disks  are  battery-backed  in  one	way or
	      another, disabling barriers may safely improve performance.  The
	      mount  options  "barrier"	 and  "nobarrier"  can also be used to
	      enable or	disable	barriers,  for	consistency  with  other  ext4
	      mount options.

	      The ext4 filesystem enables write	barriers by default.

       inode_readahead_blks=n
	      This tuning parameter controls the maximum number	of inode table
	      blocks that ext4's inode table readahead algorithm will pre-read
	      into  the	 buffer	 cache.	  The  value must be a power of	2. The
	      default value is 32 blocks.

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

       delalloc
	      Deferring	block allocation until write-out time.

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

       max_batch_time=usec
	      Maximum amount of	time ext4 should wait for additional  filesys-
	      tem  operations  to  be  batch together with a synchronous write
	      operation. Since a synchronous write operation is	going to force
	      a	 commit	 and then a wait for the I/O complete, it doesn't cost
	      much, and	can be a huge throughput win,  we  wait	 for  a	 small
	      amount of	time to	see if any other transactions can piggyback on
	      the synchronous write. The algorithm used	is designed  to	 auto-
	      matically	 tune  for  the	 speed	of  the	disk, by measuring the
	      amount of	time (on average) that it takes	to finish committing a
	      transaction. Call	this time the "commit time".  If the time that
	      the transaction has been running is less than the	 commit	 time,
	      ext4 will	try sleeping for the commit time to see	if other oper-
	      ations will join the transaction.	The commit time	is  capped  by
	      the max_batch_time, which	defaults to 15000us (15ms). This opti-
	      mization can be turned off entirely by setting max_batch_time to
	      0.

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

       journal_ioprio=prio
	      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.

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

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

	      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
	      delayed 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.

       discard/nodiscard
	      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.

       nouid32
	      Disables	32-bit	UIDs  and  GIDs.  This is for interoperability
	      with  older kernels which	only store and expect 16-bit values.

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

       block_validity/noblock_validity
	      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.

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

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

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

       blocksize={512|1024|2048}
	      Set blocksize (default 512). This	option is obsolete.

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

       umask=value
	      Set  the	umask  (the  bitmask  of  the permissions that are not
	      present).	The default is the umask of the	current	process.   The
	      value is given in	octal.

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

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

       allow_utime=value
	      This option controls the permission check	of mtime/atime.

	      20     If	 current  process  is in group of file's group ID, you
		     can change	timestamp.

	      2	     Other users can change timestamp.

	      The default is set from `dmask' option.  (If  the	 directory  is
	      writable,	utime(2) is also allowed. I.e. ~dmask &	022)

	      Normally	utime(2)  checks current process is owner of the file,
	      or it has	CAP_FOWNER capability.	 But  FAT  filesystem  doesn't
	      have  uid/gid  on	 disk, so normal check is too inflexible. With
	      this option you can relax	it.

       check=value
	      Three different levels of	pickyness can be chosen:

	      r[elaxed]
		     Upper and lower case are accepted	and  equivalent,  long
		     name   parts  are	truncated  (e.g.   verylongname.foobar
		     becomes verylong.foo), leading and	 embedded  spaces  are
		     accepted in each name part	(name and extension).

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

	      s[trict]
		     Like "normal", but	names may not contain long  parts  and
		     special  characters that are sometimes used on Linux, but
		     are not accepted by MS-DOS	are rejected. (+,  =,  spaces,
		     etc.)

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

       conv={b[inary]|t[ext]|a[uto]}
	      The fat filesystem can perform CRLF<-->NL	(MS-DOS	text format to
	      UNIX  text  format) conversion in	the kernel. The	following con-
	      version modes are	available:

	      binary no	translation is performed.  This	is the default.

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

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

	      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.

       cvf_format=module
	      Forces the driver	to use the CVF (Compressed Volume File)	module
	      cvf_module  instead  of  auto-detection.	If the kernel supports
	      kmod, the	cvf_format=xxx option also controls on-demand CVF mod-
	      ule loading.  This option	is obsolete.

       cvf_option=option
	      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).

       discard
	      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.

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

       iocharset=value
	      Character	set to use for converting between 8 bit	characters and
	      16 bit Unicode characters. The default is	iso8859-1.  Long file-
	      names are	stored on disk in Unicode format.

       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
	      internally).  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!

       showexec
	      If  set, the execute permission bits of the file will be allowed
	      only if the extension part of the	name is	.EXE, .COM,  or	 .BAT.
	      Not set by default.

       sys_immutable
	      If  set,	ATTR_SYS attribute on FAT is handled as	IMMUTABLE flag
	      on Linux.	 Not set by default.

       flush  If set, the filesystem will try to flush to disk more early than
	      normal.  Not set by default.

       usefree
	      Use the "free clusters" value stored on FSINFO. It'll be used to
	      determine	number of free clusters	 without  scanning  disk.  But
	      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
	      process.

       session=n
	      Select the CDROM session to mount.   Defaults  to	 leaving  that
	      decision	to  the	CDROM driver.  This option will	fail with any-
	      thing but	a CDROM	as underlying device.

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

       quiet  Don't complain about invalid mount options.

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

       umask=value
	      Set the umask (the bitmask  of  the  permissions	that  are  not
	      present).	 The default is	the umask of the current process.  The
	      value is given in	octal.

       case={lower|asis}
	      Convert all files	names to lower case, or	leave them.  (Default:
	      case=lower.)

       conv={binary|text|auto}
	      For  conv=text,  delete some random CRs (in particular, all fol-
	      lowed by NL) when	reading	a file.	 For conv=auto,	choose more or
	      less   at	  random   between  conv=binary	 and  conv=text.   For
	      conv=binary, just	read what is in	the file. This is the default.

       nocheck
	      Do not abort mounting when certain consistency checks fail.

Mount options for iso9660
       ISO  9660 is a standard describing a filesystem structure to be used on
       CD-ROMs.	(This filesystem type is also seen on some DVDs. See also  the
       udf filesystem.)

       Normal  iso9660	filenames  appear  in  a  8.3  format  (i.e., DOS-like
       restrictions on filename	length), and in	addition all characters	are in
       upper  case.   Also  there  is no field for file	ownership, protection,
       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.

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

       check={r[elaxed]|s[trict]}
	      With check=relaxed, a filename is	first converted	to lower  case
	      before  doing  the  lookup.   This  is  probably only meaningful
	      together with norock and map=normal.  (Default: check=strict.)

       uid=value and gid=value
	      Give all files in	the filesystem the indicated user or group id,
	      possibly	overriding  the	 information  found  in	the Rock Ridge
	      extensions.  (Default: uid=0,gid=0.)

       map={n[ormal]|o[ff]|a[corn]}
	      For non-Rock Ridge volumes, normal name translation  maps	 upper
	      to  lower	case ASCII, drops a trailing `;1', and converts	`;' to
	      `.'.  With map=off no name  translation  is  done.  See  norock.
	      (Default:	 map=normal.)	map=acorn  is like map=normal but also
	      apply Acorn extensions if	present.

       mode=value
	      For non-Rock Ridge volumes, give all files the  indicated	 mode.
	      (Default:	 read  permission  for everybody.)  Since Linux	2.1.37
	      one no longer needs to specify the mode in  decimal.  (Octal  is
	      indicated	by a leading 0.)

       unhide Also  show  hidden and associated	files.	(If the	ordinary files
	      and the associated or hidden files have the same filenames, this
	      may make the ordinary files inaccessible.)

       block={512|1024|2048}
	      Set   the	  block	  size	to  the	 indicated  value.   (Default:
	      block=1024.)

       conv={a[uto]|b[inary]|m[text]|t[ext]}
	      (Default:	conv=binary.)  Since Linux 1.3.54 this option  has  no
	      effect  anymore.	 (And non-binary settings used to be very dan-
	      gerous, possibly leading to silent data corruption.)

       cruft  If the high byte of the file length contains other garbage,  set
	      this  mount  option  to  ignore  the high	order bits of the file
	      length.  This implies that a file	cannot be larger than 16MB.

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

       sbsector=xxx
	      Session begins from sector xxx. (Since 2.3.4.)

       The following options are the same as for vfat and specifying them only
       makes  sense  when  using discs encoded using Microsoft's Joliet	exten-
       sions.

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

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

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

       resize=value
	      Resize the volume	to value blocks. JFS only supports  growing  a
	      volume,  not  shrinking  it.  This option	is only	valid during a
	      remount, when the	volume is mounted read-write. The resize  key-
	      word  with no value will grow the	volume to the full size	of the
	      partition.

       nointegrity
	      Do not write to the journal.  The	primary	use of this option  is
	      to  allow	 for  higher  performance when restoring a volume from
	      backup media. The	integrity of the volume	is not	guaranteed  if
	      the system abnormally ends.

       integrity
	      Default.	 Commit	 metadata  changes  to	the journal.  Use this
	      option to	remount	a volume where the nointegrity option was pre-
	      viously specified	in order to restore normal behavior.

       errors={continue|remount-ro|panic}
	      Define  the  behaviour  when  an	error is encountered.  (Either
	      ignore errors and	just mark the filesystem  erroneous  and  con-
	      tinue,  or  remount  the filesystem read-only, or	panic and halt
	      the system.)

       noquota|quota|usrquota|grpquota
	      These options are	accepted but ignored.

Mount options for minix
       None.

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
       iocharset=name
	      Character	 set  to  use when returning file names.  Unlike VFAT,
	      NTFS suppresses names that  contain  nonconvertible  characters.
	      Deprecated.

       nls=name
	      New name for the option earlier called iocharset.

       utf8   Use UTF-8	for converting file names.

       uni_xlate={0|1|2}
	      For  0  (or  `no'	 or  `false'), do not use escape sequences for
	      unknown Unicode characters.  For 1 (or `yes' or  `true')	or  2,
	      use vfat-style 4-byte escape sequences starting with ":".	Here 2
	      give a little-endian encoding  and  1  a	byteswapped  bigendian
	      encoding.

       posix=[0|1]
	      If enabled (posix=1), the	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
	      see.

Mount options for ramfs
       Ramfs is	a memory based filesystem. Mount it and	you have  it.  Unmount
       it  and it is gone. Present since Linux 2.3.99pre4.  There are no mount
       options.

Mount options for reiserfs
       Reiserfs	is a journaling	filesystem.

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

       hash={rupasov|tea|r5|detect}
	      Choose  which  hash  function  reiserfs  will  use to find files
	      within directories.

	      rupasov
		     A hash invented by	Yury Yu. Rupasov.  It is fast and pre-
		     serves  locality,	mapping	 lexicographically  close file
		     names to close hash values.  This option  should  not  be
		     used, as it causes	a high probability of hash collisions.

	      tea    A	 Davis-Meyer   function	   implemented	  by	Jeremy
		     Fitzhardinge.   It	 uses hash permuting bits in the name.
		     It	gets high randomness and, therefore,  low  probability
		     of	hash collisions	at some	CPU cost.  This	may be used if
		     EHASHCOLLISION errors are experienced with	the r5 hash.

	      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-
		     tem.

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

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

       noborder
	      Disable the border allocator  algorithm  invented	 by  Yury  Yu.
	      Rupasov.	This may provide performance improvements in some sit-
	      uations.

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

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

       replayonly
	      Replay the transactions which are	in the	journal,  but  do  not
	      actually mount the filesystem. Mainly used by reiserfsck.

       resize=number
	      A	remount	option which permits online expansion of reiserfs par-
	      titions.	Instructs reiserfs to assume that the device has  num-
	      ber  blocks.  This option	is designed for	use with devices which
	      are under	logical	volume management (LVM).  There	is  a  special
	      resizer	  utility     which	can	be    obtained	  from
	      ftp://ftp.namesys.com/pub/reiserfsprogs.

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

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

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

Mount options for romfs
       None.

Mount options for squashfs
       None.

Mount options for smbfs
       Just  like  nfs,	 the smbfs implementation expects a binary argument (a
       struct smb_mount_data) to the mount system call.	This argument is  con-
       structed	 by  smbmount(8)  and the current version of mount (2.12) does
       not know	anything about smbfs.

Mount options for sysv
       None.

Mount options for tmpfs
       size=nbytes
	      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%

       nr_blocks=
	      The same as size,	but in blocks of PAGE_CACHE_SIZE

       nr_inodes=
	      The  maximum  number of inodes for this instance.	The default is
	      half of the number of your physical RAM pages, or	(on a  machine
	      with  highmem)  the number of lowmem RAM pages, whichever	is the
	      lower.

       The tmpfs mount options for sizing ( size,  nr_blocks,  and  nr_inodes)
       accept  a  suffix k, m or g for Ki, Mi, Gi (binary kilo,	mega and giga)
       and can be changed on remount.

       mode=  Set initial permissions of the root directory.

       uid=   The user id.

       gid=   The group	id.

       mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
	      Set the NUMA memory allocation policy  for  all  files  in  that
	      instance	(if  the kernel	CONFIG_NUMA is enabled)	- which	can be
	      adjusted on the fly via 'mount -o	remount	...'

	      default
		     prefers to	allocate memory	from the local node

	      prefer:Node
		     prefers to	allocate memory	from the given Node

	      bind:NodeList
		     allocates memory only from	nodes in NodeList

	      interleave
		     prefers to	allocate from each node	in turn

	      interleave:NodeList
		     allocates from each node of NodeList in turn.

	      The NodeList format is a comma-separated list of decimal numbers
	      and  ranges, a range being two hyphen-separated decimal numbers,
	      the smallest and largest node numbers in the range.   For	 exam-
	      ple, mpol=bind:0-3,5,7,9-15

	      Note  that trying	to mount a tmpfs with an mpol option will fail
	      if the running kernel does not support NUMA; and	will  fail  if
	      its nodelist specifies a node which is not online.  If your sys-
	      tem relies on that tmpfs being mounted, but from	time  to  time
	      runs  a  kernel  built  without  NUMA capability (perhaps	a safe
	      recovery kernel),	or with	fewer nodes online, then it is	advis-
	      able  to	omit the mpol option from automatic mount options.  It
	      can be added later, when the tmpfs is already mounted on	Mount-
	      Point, by	'mount -o remount,mpol=Policy:NodeList MountPoint'.

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

	      ubiX:NAME
		     UBI device	number X, volume with name NAME

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

       The following mount options are available:

       bulk_read
	      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.

       no_bulk_read
	      Do not bulk-read.	This is	the default.

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

       no_chk_data_crc.
	      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.

       compr={none|lzo|zlib}
	      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.

       undelete
	      Show deleted files in lists.

       nostrict
	      Unset strict conformance.

       iocharset
	      Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

       session=
	      Set the CDROM session counting from 0. Default: last session.

       anchor=
	      Override standard	anchor location. Default: 256.

       volume=
	      Override the VolumeDesc location.	(unused)

       partition=
	      Override the PartitionDesc location. (unused)

       lastblock=
	      Set the last block of the	filesystem.

       fileset=
	      Override the fileset block location. (unused)

       rootdir=
	      Override the root	directory location. (unused)

Mount options for ufs
       ufstype=value
	      UFS is a 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.

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

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

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

       onerror=value
	      Set behaviour on error:

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

	      [lock|umount|repair]
		     These mount options don't do anything at present; when an
		     error is encountered only a console message is printed.

Mount options for umsdos
       See mount options for msdos.  The dotsOK	option is explicitly killed by
       umsdos.

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

       uni_xlate
	      Translate	 unhandled  Unicode  characters	 to  special   escaped
	      sequences.   This	lets you backup	and restore filenames that are
	      created with any Unicode characters. Without this	option,	a  '?'
	      is used when no translation is possible. The escape character is
	      ':' because it is	otherwise illegal on the vfat filesystem.  The
	      escape  sequence	that gets used,	where u	is the unicode charac-
	      ter, is: ':', (u & 0x3f),	((u>>6)	& 0x3f), (u>>12).

       posix  Allow two	files with names  that	only  differ  in  case.	  This
	      option is	obsolete.

       nonumtail
	      First  try  to make a short name without sequence	number,	before
	      trying name~num.ext.

       utf8   UTF8 is the filesystem safe 8-bit	encoding of  Unicode  that  is
	      used  by	the console. It	can be enabled for the filesystem with
	      this option or disabled with utf8=0, utf8=no or  utf8=false.  If
	      `uni_xlate' gets set, UTF8 gets disabled.

       shortname={lower|win95|winnt|mixed}

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

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

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

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

	      mixed  Display the short name as is; store a long	name when  the
		     short  name  is  not  all	upper  case.  This mode	is the
		     default 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
	      usbfs  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
       None.

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

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

       attr2|noattr2
	      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
	      selected	(either	 when setting or removing extended attributes)
	      the on-disk superblock feature bit  field	 will  be  updated  to
	      reflect this format being	in use.

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

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

       barrier|nobarrier
	      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.

       discard|nodiscard
	      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
	      severe.

       grpid|bsdgroups|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 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.

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

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

       inode32|inode64
	      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-
	      fied.

       largeio|nolargeio
	      If "nolargeio" is	specified, the optimal I/O reported in st_blk-
	      size by stat(2) will be as  small	 as  possible  to  allow  user
	      applications  to	avoid inefficient read/modify/write I/O.  This
	      is typically the page size of the	machine, as this is the	granu-
	      larity of	the page cache.

	      If  "largeio"  specified,	 a  filesystem that was	created	with a
	      "swidth" specified will return the "swidth" value	(in bytes)  in
	      st_blksize. If the filesystem does not have a "swidth" specified
	      but does specify an "allocsize" then "allocsize" (in bytes) will
	      be  returned  instead. Otherwise the behaviour is	the same as if
	      "nolargeio" was specified.

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

	      The default value	is 8 buffers.

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

       logbsize=value
	      Set the size of each in-memory log  buffer.   The	 size  may  be
	      specified	 in  bytes,  or	in kilobytes with a "k"	suffix.	 Valid
	      sizes for	version	1 and version 2	logs are 16384 (16k) and 32768
	      (32k).  Valid sizes for version 2	logs also include 65536	(64k),
	      131072 (128k) and	262144 (256k). The logbsize must be an integer
	      multiple of the log stripe unit configured at mkfs time.

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

       logdev=deviceandrtdev=device
	      Use an external log (metadata journal) and/or real-time  device.
	      An  XFS  filesystem has up to three parts: a data	section, a log
	      section, and a real-time	section.   The	real-time  section  is
	      optional,	and the	log section can	be separate from the data sec-
	      tion or contained	within it.

       noalign
	      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.

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

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

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

       uquota/usrquota/uqnoenforce/quota
	      User  disk  quota	 accounting  enabled,  and limits (optionally)
	      enforced.	 Refer to xfs_quota(8) for further details.

       gquota/grpquota/gqnoenforce
	      Group disk quota	accounting  enabled  and  limits  (optionally)
	      enforced.	 Refer to xfs_quota(8) for further details.

       pquota/prjquota/pqnoenforce
	      Project  disk  quota  accounting enabled and limits (optionally)
	      enforced.	 Refer to xfs_quota(8) for further details.

       sunit=value and swidth=value
	      Used to specify the stripe unit and width	for a RAID device or a
	      stripe  volume.	"value"	 must  be  specified in	512-byte block
	      units. These options are only relevant to	filesystems that  were
	      created with non-zero data alignment parameters.

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

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

       swalloc
	      Data  allocations	 will be rounded up to stripe width boundaries
	      when the current end of file is being extended and the file size
	      is larger	than the stripe	width size.

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

Mount options for xiafs
       None. Although nothing is wrong with xiafs, it is not used much,	and is
       not  maintained.	 Probably  one	shouldn't use it.  Since Linux version
       2.1.21 xiafs is no longer part of the kernel source.

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

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

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

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

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

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

	      mount /tmp/disk.img /mnt

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

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

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

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

RETURN CODES
       mount has the following return codes (the bits can be ORed):

       0      success

       1      incorrect	invocation or permissions

       2      system error (out	of memory, cannot fork,	no more	loop devices)

       4      internal mount bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

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

NOTES
       The syntax of external mount helpers is:

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

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

FILES
       /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

ENVIRONMENT
       LIBMOUNT_FSTAB=<path>
	      overrides	the default location of	the fstab file

       LIBMOUNT_MTAB=<path>
	      overrides	the default location of	the mtab file

       LIBMOUNT_DEBUG=0xffff
	      enables debug output

SEE ALSO
       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)

BUGS
       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
       example,	but you	can't change gid or umask for the fatfs).

       It  is  possible	that files /etc/mtab and /proc/mounts don't match. The
       first file is based only	on the mount command options, but the  content
       of the second file also depends on the kernel and others	settings (e.g.
       remote NFS server. In particular	case the  mount	 command  may  reports
       unreliable  information	about  a  NFS mount point and the /proc/mounts
       file usually contains more reliable information.)

       Checking	files on NFS filesystem	referenced by file  descriptors	 (i.e.
       the  fcntl  and	ioctl  families	of functions) may lead to inconsistent
       result due to the lack of consistency check in kernel even if  noac  is
       used.

       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.

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

AUTHORS
       Karel Zak <kzak@redhat.com>

AVAILABILITY
       The  mount  command  is part of the util-linux package and is available
       from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux			 January 2012			      MOUNT(8)

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

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