mount manpage

Search topic Section

MOUNT(8)		     System Administration		      MOUNT(8)

       mount - mount a filesystem

       mount [-lhV]

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

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

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

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

       The standard form of the mount command, is

	      mount -t type device dir

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

       If only directory or device is given, for example:

	      mount /dir

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

	      mount --target /mountpoint

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

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

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

       The device indication.
	      Most devices are indicated by a file name (of  a	block  special
	      device),	like /dev/sda1, but there are other possibilities. For
	      example, in the case of an  NFS  mount,  device  may  look  like
	      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-

	      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


		     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-

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

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

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

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

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

	      Note  that  moving  a  mount  residing  under  a shared mount is
	      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,

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

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

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

       Command line options available for the mount command:

       -V, --version
	      Output version.

       -h, --help
	      Print a help message.

       -v, --verbose
	      Verbose mode.

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

       -F, --fork
	      (Used  in	 conjunction  with -a.)	 Fork off a new incarnation of
	      mount for each device.  This will do  the	 mounts	 on  different
	      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

       -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-

	      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-

	      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-

		     mount -a -O no_netdev

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

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

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

		     mount -a -t ext2 -O _netdev

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

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

		     mount LABEL=mydisk -o noatime,nouser

	      For  more	 details, see FILESYSTEM INDEPENDENT MOUNT OPTIONS and

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

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

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

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

       Some  of these  options	could be enabled or disabled by default in the
       system kernel.  To  check  the  current	setting	 see  the  options  in
       /proc/mounts.   Note that filesystems also have per-filesystem specific
       default mount options (see for  example	tune2fs	 -l  output  for  extN

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

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

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

	      Do not update inode access times on this filesystem  (e.g.,  for
	      faster access on the news spool to speed up news servers).

       auto   Can be mounted with the -a option.

       noauto Can  only	 be  mounted  explicitly (i.e., the -a option will not
	      cause the filesystem to be mounted).

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

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

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

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

	      You  can	set  the  default security context for unlabeled files
	      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-

	      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-

	      For more details, see selinux(8).

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

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

       dev    Interpret character or block special devices on the filesystem.

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

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

	      Do not update directory inode access times on this filesystem.

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

       exec   Permit execution of binaries.

       noexec Do  not  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).

	      Every  time  the	inode is modified, the i_version field will be

	      Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

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

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

	      Do  not  use  relatime  feature.	See also the strictatime mount

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

	      Use  the	kernel's  default  behaviour  for  inode  access  time

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

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

       silent Turn on the silent flag.

       loud   Turn off the silent flag.

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

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

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

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

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

	      mount -o remount,rw  /dir

	      After this call mount reads fstab (or  mtab)  and	 merges	 these
	      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

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

	      Allow  to	 make  a  target  directory (mountpoint). The optional
	      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.

       The following options apply only to certain filesystems.	 We sort  them
       by filesystem. They all follow the -o flag.

       What  options  are supported depends a bit on the running kernel.  More
       info  may  be  found  in	 the  kernel  source  subdirectory  Documenta-

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

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

Mount options for affs
       uid=value and gid=value
	      Set  the owner and group of the root of the filesystem (default:
	      uid=gid=0, but with option uid or gid without  specified	value,
	      the uid and gid of the current process are taken).

       setuid=value and setgid=value
	      Set the owner and group of all files.

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

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

       usemp  Set uid and gid of the root of the filesystem to the uid and gid
	      of the mount point upon the first sync or umount, and then clear
	      this option. Strange...

	      Print an informational message for each successful mount.

	      Prefix used before volume name, when following a link.

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

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

	      Give explicitly the location of the root block.

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

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

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

Mount options for coherent

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

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

	      Sets the mode of the mountpoint.

Mount options for devpts
       The devpts filesystem is a pseudo filesystem, traditionally mounted  on
       /dev/pts.   In  order  to  acquire  a  pseudo terminal, a process opens
       /dev/ptmx; the number of the pseudo terminal is then made available  to
       the   process  and  the	pseudo	terminal  slave	 can  be  accessed  as

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

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

	      Create a	private	 instance  of  devpts  filesystem,  such  that
	      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-

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


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

	      With  the	 support  for multiple instances of devpts (see newin-
	      stance option above), each instance has a private ptmx  node  in
	      the root of the devpts filesystem (typically /dev/pts/ptmx).

	      For compatibility with older versions of the kernel, the default
	      mode of the new ptmx node is 0000.  ptmxmode=value  specifies  a
	      more  useful  mode  for  the ptmx node and is highly recommended
	      when the newinstance option is specified.

	      This option is only implemented in linux kernel versions	start-
	      ing  with	 2.6.29.  Further  this	 option	 is valid only if CON-
	      FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel  configu-

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

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

	      Support POSIX Access Control Lists (or not).

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

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

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

	      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.

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

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

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

       resgid=n and resuid=n
	      The ext2 filesystem reserves a certain percentage of the	avail-
	      able space (by default 5%, see mke2fs(8) and tune2fs(8)).	 These
	      options determine who can use the	 reserved  blocks.   (Roughly:
	      whoever  has  the	 specified  uid,  or  belongs to the specified

       sb=n   Instead of block 1, use block n as  superblock.  This  could  be
	      useful  when  the filesystem has been damaged.  (Earlier, copies
	      of the superblock would be made every 8192 blocks: in  block  1,
	      8193,  16385,  ...  (and	one  got  thousands of copies on a big
	      filesystem).  Since  version  1.08,  mke2fs  has	a  -s  (sparse
	      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".

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

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

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

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

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

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

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

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

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

		     Data ordering is not preserved - data may be written into
		     the main filesystem after its metadata has been committed
		     to the journal.  This is  rumoured	 to  be	 the  highest-
		     throughput	 option.   It  guarantees  internal filesystem
		     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-

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

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

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

	      Apart  from  the	old quota system (as in ext2, jqfmt=vfsold aka
	      version 1 quota) ext3 also supports journaled quotas (version  2
	      quota). jqfmt=vfsv0 enables journaled quotas. For journaled quo-
	      tas    the    mount    options	 usrjquota=aquota.user	   and
	      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.

	      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.

	      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.

	      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.

	      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

	      Deferring block allocation until write-out time.

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

	      Maximum  amount of time ext4 should wait for additional filesys-
	      tem operations to be batch together  with	 a  synchronous	 write
	      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

	      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.

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

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

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

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

	      or worse yet

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

	      If  auto_da_alloc	 is enabled, ext4 will detect 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.

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

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

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

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

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

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

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

	      Set blocksize (default 512). This option is obsolete.

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

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

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

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

	      This option controls the permission check of mtime/atime.

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

	      2	     Other users can change timestamp.

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

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

	      Three different levels of pickyness can be chosen:

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

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

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

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

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

	      binary no translation is performed.  This is the default.

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

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

	      Programs that do computed lseeks won't like in-kernel text  con-
	      version.	 Several  people  have	had  their data ruined by this
	      translation. Beware!

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

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

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

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

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

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

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

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

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

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

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

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

	      Use the "free clusters" value stored on FSINFO. It'll be used to
	      determine	 number	 of  free  clusters without scanning disk. But
	      it's not used by default, because recent Windows don't update it
	      correctly	 in  some case. If you are sure the "free clusters" on
	      FSINFO is correct, by this option you can avoid scanning disk.

       dots, nodots, dotsOK=[yes|no]
	      Various misguided attempts to force Unix or DOS conventions onto
	      a FAT filesystem.

Mount options for hfs
       creator=cccc, type=cccc
	      Set  the	creator/type  values as shown by the MacOS finder used
	      for creating new files.  Default values: '????'.

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

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

	      Select  the  CDROM  session  to mount.  Defaults to leaving that
	      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.)

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

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

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

	      Do not abort mounting when certain consistency checks fail.

Mount options for iso9660
       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.

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

	      With check=relaxed, a filename is first converted to lower  case
	      before  doing  the  lookup.   This  is  probably only meaningful
	      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.)

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

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

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

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

	      (Default: conv=binary.)  Since Linux 1.3.54 this option  has  no
	      effect  anymore.	 (And non-binary settings used to be very dan-
	      gerous, possibly leading to silent data corruption.)

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

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

	      Session begins from sector xxx. (Since 2.3.4.)

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

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

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

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

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

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

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

	      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.)

	      These options are accepted but ignored.

Mount options for minix

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

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

Mount options for nfs and nfs4
       See  the options section of the nfs(5) man page (nfs-utils package must
       be installed).

       The nfs and nfs4 implementation expects a  binary  argument  (a	struct
       nfs_mount_data)	to the mount system call. This argument is constructed
       by mount.nfs(8) and the current version of mount (2.13) does  not  know
       anything about nfs and nfs4.

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

	      New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

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

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

       uid=value, gid=value and umask=value
	      Set  the	file permission on the filesystem.  The umask value is
	      given in octal.  By default, the files are owned by root and not
	      readable by somebody else.

Mount options for proc
       uid=value and gid=value
	      These options are recognized, but have no effect as far as I can

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

Mount options for reiserfs
       Reiserfs is a journaling filesystem.

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

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

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

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

	      r5     A modified version of the rupasov hash.  It  is  used  by
		     default  and is the best choice unless the filesystem has
		     huge directories and unusual file-name patterns.

	      detect Instructs mount to detect which hash function is  in  use
		     by	 examining the filesystem being mounted,  and to write
		     this information into the reiserfs	 superblock.  This  is
		     only  useful on the first mount of an old format filesys-

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

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

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

       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.

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

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

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

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

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

Mount options for romfs

Mount options for squashfs

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

Mount options for sysv

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

	      The same as size, but in blocks of PAGE_CACHE_SIZE

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

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

       mode=  Set initial permissions of the root directory.

       uid=   The user id.

       gid=   The group id.

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

		     prefers to allocate memory from the local node

		     prefers to allocate memory from the given Node

		     allocates memory only from nodes in NodeList

		     prefers to allocate from each node in turn

		     allocates from each node of NodeList in turn.

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

	      Note  that trying to mount a tmpfs with an mpol option will fail
	      if the running kernel does not support NUMA; and	will  fail  if
	      its nodelist specifies a node which is not online.  If your sys-
	      tem relies on that tmpfs being mounted, but from	time  to  time
	      runs  a  kernel  built  without  NUMA capability (perhaps a safe
	      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

		     UBI device number X, volume with name NAME

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

       The following mount options are available:

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

	      Do not bulk-read. This is the default.

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

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

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

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

	      Show deleted files in lists.

	      Unset strict conformance.

	      Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

	      Override standard anchor location. Default: 256.

	      Override the VolumeDesc location. (unused)

	      Override the PartitionDesc location. (unused)

	      Set the last block of the filesystem.

	      Override the fileset block location. (unused)

	      Override the root directory location. (unused)

Mount options for ufs
	      UFS is a filesystem widely used in different operating  systems.
	      The  problem  are differences among implementations. Features of
	      some implementations are undocumented, so its hard to  recognize
	      the type of ufs automatically.  That's why the user must specify
	      the type of ufs by mount option.	Possible values are:

	      old    Old format of  ufs,  this	is  the	 default,  read	 only.
		     (Don't forget to give the -r option.)

	      44bsd  For  filesystems  created	by  a  BSD-like	 system	 (Net-

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

	      5xbsd  Synonym for ufs2.

	      sun    For filesystems created by SunOS or Solaris on Sparc.

	      sunx86 For filesystems created by Solaris on x86.

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

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

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

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

	      Set behaviour on error:

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

		     These mount options don't do anything at present; when an
		     error is encountered only a console message is printed.

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

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

	      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.

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

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


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

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

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

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

	      mixed  Display the short name as is; store a long name when  the
		     short  name  is  not  all	upper  case.  This mode is the
		     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

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

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

	      The options enable/disable an "opportunistic" improvement to  be
	      made  in	the way inline extended attributes are stored on-disk.
	      When the new form is used for  the  first	 time  when  attr2  is
	      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

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

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

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

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

	      These options define what group ID a newly  created  file	 gets.
	      When  grpid  is  set,  it takes the group ID of the directory in
	      which it is created; otherwise it takes the fsgid of the current
	      process,	unless	the directory has the setgid bit set, in which
	      case it takes the gid from the parent directory, and  also  gets
	      the setgid bit set if it is a directory itself.

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

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

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

	      When inode64 is specified, it indicates that XFS is  allowed  to
	      create inodes at any location in the filesystem, including those
	      which will result in inode numbers occupying more than  32  bits
	      of significance.

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

	      If "nolargeio" is specified, the optimal I/O reported in st_blk-
	      size  by	stat(2)	 will  be  as  small as possible to allow user
	      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.

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

	      The default value is 8 buffers.

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

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

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

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

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

	      The filesystem will be mounted without running log recovery.  If
	      the filesystem was not cleanly unmounted, it  is	likely	to  be
	      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

       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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	      mount /tmp/disk.img /mnt

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

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

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

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

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

       0      success

       1      incorrect invocation or permissions

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

       4      internal mount bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

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

       The syntax of external mount helpers is:

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

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

       /etc/fstab	 filesystem table

       /etc/mtab	 table of mounted filesystems

       /etc/mtab~	 lock file

       /etc/mtab.tmp	 temporary file

       /etc/filesystems	 a list of filesystem types to try

	      overrides the default location of the fstab file

	      overrides the default location of the mtab file

	      enables debug output

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

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

       Some Linux filesystems don't support -o sync and -o dirsync (the	 ext2,
       ext3,  fat  and	vfat  filesystems do support synchronous updates (a la
       BSD) when mounted with the sync option).

       The -o remount may not be able to change mount parameters (all  ext2fs-
       specific	 parameters,  except  sb,  are	changeable with a remount, for
       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

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

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

       Karel Zak <kzak@redhat.com>

       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)