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MOUNT(8)		     System Administration		      MOUNT(8)

       mount - mount a filesystem

       mount [-lhV]

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

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

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

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

       The standard form of the mount command, is

	      mount -t type device dir

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

       If only directory or device is given, for example:

	      mount /dir

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

	      mount --target /mountpoint

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

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

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

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

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

	      The recommended setup is to use tags (e.g. LABEL=<label>) rather
	      than  /dev/disk/by-{label,uuid,partuuid,partlabel} udev symlinks
	      in the /etc/fstab file. The tags are more readable,  robust  and
	      portable. The mount(8) command internally uses udev symlinks, so
	      the use of 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 /dir
	      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.	 An 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
	      Display version information and exit.

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

       -v, --verbose
	      Verbose mode.

       -a, --all
	      Mount all filesystems (of the given types)  mentioned  in	 fstab
	      (except for those whose line contains the noauto keyword).

       -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. Currently it's supported by the
	      mount.nfs mount helper only.

       --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
	      '' is deprecated).

	      For most types all the mount program has to do is issue a simple
	      mount(2) system call, and no detailed knowledge of the  filesys‐
	      tem  type is required.  For a few types however (like nfs, nfs4,
	      cifs, smbfs, ncpfs) 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

       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

       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  1 k
	      units.  Thus,  if	 you  want  to	use  logical  block 32768 on a
	      filesystem with 4 k blocks, use "sb=131072".

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

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

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

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

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

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

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

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

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

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

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

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

       barrier=0 / barrier=1
	      This 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 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,  norecovery,  noload,	data,  commit,	orlov,
       oldalloc,   [no]user_xattr  [no]acl,  bsddf,  minixdf,  debug,  errors,
       data_err, grpid, bsdgroups, nogrpid  sysvgroups,	 resgid,  resuid,  sb,
       quota,  noquota,	 grpquota, usrquota usrjquota, grpjquota and jqfmt are
       backwardly compatible with ext3 or ext2.

	      Enable checksumming of  the  journal  transactions.   This  will
	      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 15000 µs (15 ms). This
	      optimization   can   be	turned	 off   entirely	  by   setting
	      max_batch_time to 0.

	      This  parameter  sets the commit time (as described above) to be
	      at least	min_batch_time.	 It  defaults  to  zero	 microseconds.
	      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("")/write(fd,..)/close(fd)/ rename("",

	      or worse yet

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

	      If auto_da_alloc is enabled, ext4 will detect  the  replace-via-
	      rename  and  replace-via-truncate	 patterns  and	force that any
	      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.

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

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

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

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

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

	      Controls whether or not ext4 should use the DIO read locking. If
	      the dioread_nolock option is specified ext4 will allocate 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).

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

	      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, 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 and execute  permission  for  everybody.)	 Since
	      Linux 2.1.37 one no longer needs to specify the mode in decimal.
	      (Octal is indicated by a leading 0.)

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

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

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

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

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

	      Session begins from sector xxx. (Since 2.3.4.)

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

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

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

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

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

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

	      Default.	Commit metadata changes	 to  the  journal.   Use  this
	      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  (default  size is 64 KiB).	 Valid
	      values for this option are page size (typically  4 KiB)  through
	      to 1 GiB, 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	 clus‐
	      ters  and keeps them around on disk.  When noikeep is specified,
	      empty inode clusters are returned to the free space pool.

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

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

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

	      If "nolargeio" is specified, the optimal I/O reported in st_blk‐
	      size  by	stat(2)	 will  be  as  small as possible to allow user
	      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 relevant 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 (16 k) and
	      32768 (32 k).  Valid sizes for version 2 logs also include 65536
	      (64 k),  131072 (128 k) and 262144 (256 k). The logbsize must be
	      an integer multiple of the log stripe unit  configured  at  mkfs

	      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).

       The  command mount does not pass mount options unbindable, runbindable,
       private, rprivate, slave, rslave, shared, rshared, auto,	 noauto,  com‐
       ment,  x-*,  loop,  offset and sizelimit to mount.<suffix> helpers. The
       all others options are used in comma delimited list as argument for the
       option -o.

       /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 <>

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

util-linux			 January 2012			      MOUNT(8)

List of man pages available for Archlinux

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