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MOUNT(8)		   Linux Programmer's Manual		      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.

       The listing and help.
	      Three forms of invocation do not actually mount anything:

	      mount -h
		     prints a help message

	      mount -V
		     prints a version string

	      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 volume LABEL or UUID (see the -L and -U options

	      The  recommended	setup  is  to use LABEL=<label> or UUID=<uuid>
	      tags rather than /dev/disk/by-{label,uuid} udev symlinks in  the
	      /etc/fstab  file.	 The tags are more readable, robust and porta‐
	      ble. The mount(8) command internally uses udev symlinks, so  use
	      the  symlinks  in /etc/fstab is not advantage over LABEL=/UUID=.
	      For more details see libblkid(3).

	      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 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) 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).

	      This call attaches only (part of) a single filesystem, not  pos‐
	      sible  submounts.	 The entire file hierarchy including submounts
	      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

       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.

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

		     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

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

       Command line options available for the mount command:

       -V, --version
	      Output version.

       -h, --help
	      Print a help message.

       -v, --verbose
	      Verbose mode.

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

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

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

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

       -l     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.

	      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 absolut paths.

       -p, --pass-fd num
	      In case of a loop mount with  encryption,	 read  the  passphrase
	      from file descriptor num instead of from the terminal.

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

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

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

       -U 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, --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 depreacated).

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

	      If no -t option is given, or if  the  auto  type	is  specified,
	      mount  will try to guess the desired type.  Mount uses the blkid
	      or volume_id 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.

	      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.  Warning: the probing uses a
	      heuristic (the presence of appropriate `magic'), and could  rec‐
	      ognize  the  wrong  filesystem  type, possibly with catastrophic
	      consequences. If your data  is  valuable,	 don't	ask  mount  to

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

		     mount -a -t nomsdos,ext

	      mounts all filesystems except those of type msdos and ext.

       -O, --test-opts opts
	      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 because vis‐
	      able  to	userspace. This was found to be useful for things like
	      stateless linux.

	      For more details, see selinux(8)

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

       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.)

       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  writeable.	 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.

	      Like  _netdev,  except  "fsck  -a" checks this filesystem during

       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

       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.  There are no mount options.

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.)

	      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.

       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.

	      These options are accepted but ignored.

       nobh   Do not attach buffer_heads to file pagecache. (Since 2.5.49.)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       barrier=0 / barrier=1
	      This enables/disables barriers.	barrier=0  disables  it,  bar‐
	      rier=1 enables it.  Write barriers enforce proper on-disk order‐
	      ing of journal commits, making volatile disk write  caches  safe
	      to  use,	at  some  performance  penalty.	  The  ext3 filesystem
	      enables write barriers by default.  Be sure to  enable  barriers
	      unless your disks are battery-backed one way or another.	Other‐
	      wise you risk filesystem corruption in case of power failure.

	      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.

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

       The   options  journal_dev,  noload,  data,  commit,  orlov,  oldalloc,
       [no]user_xattr [no]acl, bsddf, minixdf, debug, errors, data_err, grpid,
       bsdgroups,  nogrpid  sysvgroups,	 resgid,  resuid,  sb, quota, noquota,
       grpquota, usrquota and [no]bh are backwardly compatible	with  ext3  or

	      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

	      Update the ext4 filesystem's journal to the current format.

       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 allocation 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  transactoin	has been running is less than the commit time,
	      ext4 will try sleeping for the commit time to see if other oper‐
	      ations  will  join the transaction. The commit time is capped by
	      the max_batch_time, which defaults to 15000us (15ms). This opti‐
	      mization can be turned off entirely by setting max_batch_time to

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

	      The I/O priority (from 0 to 7, where 0 is the  highest  priorty)
	      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 noauto_da_alloc
	      replacing existing 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 commited.  This provides roughly the same level  of
	      guarantees  as  ext3,  and avoids the "zero-length" problem that
	      can happen when a system crashes before the  delayed  allocation
	      blocks are forced to disk.

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

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

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

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

	      Controls whether or not ext4 should use the DIO read locking. If
	      the dioread_nolock option is specified ext4 will allocate unini‐
	      tialized extent before buffer write and convert  the  extent  to
	      initialized  after IO completes.	This approach allows ext4 code
	      to avoid using inode mutex, which improves scalability  on  high
	      speed  storages. However this does not work with nobh option and
	      the mount will fail. Nor does it work with data  journaling  and
	      dioread_nolock  option will be ignored with kernel warning. Note
	      that dioread_nolock code path  is	 only  used  for  extent-based
	      files.  Because of the restrictions this options comprises it is
	      off by default (e.g. dioread_lock).

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

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

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

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

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

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

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

	      This option controls the permission check of mtime/atime.

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

	      2	     Other users can change timestamp.

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

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

	      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.

       tz=UTC This option disables the conversion of timestamps between	 local
	      time  (as	 used  by  Windows  on	FAT) and UTC (which Linux uses
	      internally).  This is particularly useful when mounting  devices
	      (like digital cameras) that are set to UTC in order to avoid the
	      pitfalls of local time.

       quiet  Turn on the quiet flag.  Attempts to chown or chmod files do not
	      return errors, although they fail. Use with caution!

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

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

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

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

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

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

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

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

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

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

       quiet  Don't complain about invalid mount options.

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

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

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

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

	      Do not abort mounting when certain consistency checks fail.

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

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

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

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

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

	      With  check=relaxed, a filename is first converted to lower case
	      before doing the	lookup.	  This	is  probably  only  meaningful
	      together with norock and map=normal.  (Default: check=strict.)

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

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

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

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

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

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

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

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

	      Session begins from sector xxx. (Since 2.3.4.)

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

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

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

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

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

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

	      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 writeable 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 unconvertible 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	journalling.  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  journalling	operations,  save  for
	      actual  writes  into  its	 journalling  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‐

	      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 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. This
		     mode is the default.

	      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.

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 64KiB).  Valid val‐
	      ues for this option are page size (typically  4KiB)  through  to
	      1GiB, inclusive, in power-of-2 increments.

	      The  options enable/disable (default is enabled) an "opportunis‐
	      tic"  improvement	 to  be	 made  in  the	way  inline   extended
	      attributes  are  stored  on-disk.	 When the new form is used for
	      the first time (by setting or removing extended attributes)  the
	      on-disk  superblock feature bit field will be updated to reflect
	      this format being in use.

	      Enables the use of block layer write barriers  for  writes  into
	      the  journal  and	 unwritten extent conversion.  This allows for
	      drive level write caching to be enabled, for devices  that  sup‐
	      port write barriers.

       dmapi  Enable the DMAPI (Data Management API) event callouts.  Use with
	      the mtpt option.

       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.

	      Sets  the	 number	 of hash buckets available for hashing the in-
	      memory inodes of the specified mount point.  If a value of  zero
	      is  used,	 the  value  selected by the default algorithm will be
	      displayed in /proc/mounts.

	      When inode clusters are emptied of inodes, keep them  around  on
	      the  disk (ikeep) - this is the traditional XFS behaviour and is
	      still the default for now.   Using  the  noikeep	option,	 inode
	      clusters are returned to the free space pool.

	      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.  This is
	      provided for backwards compatibility, but	 causes	 problems  for
	      backup applications that cannot handle large inode numbers.

	      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.  If
	      largeio is specified, a filesystem that has 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.
	      If neither of these two options are specified,  then  filesystem
	      will behave 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 for filesys‐
	      tems with a blocksize of 64KiB, 4 buffers for filesystems with a
	      blocksize of 32KiB, 3 buffers for filesystems with  a  blocksize
	      of 16KiB and 2 buffers for all other configurations.  Increasing
	      the number of buffers may increase performance on some workloads
	      at  the  cost  of the memory used for the additional log buffers
	      and their associated control structures.

	      Set the size of each in-memory log buffer.  Size may  be	speci‐
	      fied  in	bytes, or in kilobytes with a "k" suffix.  Valid sizes
	      for version 1 and version 2  logs	 are  16384  (16k)  and	 32768
	      (32k).  Valid sizes for version 2 logs also include 65536 (64k),
	      131072 (128k) and 262144 (256k).	The default value for machines
	      with more than 32MiB of memory is 32768, machines with less mem‐
	      ory use 16384 by default.

       logdev=device and rtdev=device
	      Use an external log (metadata journal) and/or real-time  device.
	      An  XFS  filesystem has up to three parts: a data section, a log
	      section, and a real-time	section.   The	real-time  section  is
	      optional, and the log section can be separate from the data sec‐
	      tion or contained within it.  Refer to xfs(5).

	      Use with the dmapi option. The  value  specified	here  will  be
	      included in the DMAPI mount event, and should be the path of the
	      actual mountpoint that is used.

	      Data allocations will not be aligned at stripe unit boundaries.

	      Access timestamps are not updated when a file is read.

	      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 filesystems using the filesystem
	      uuid.  This is useful to mount LVM snapshot volumes.

	      Make O_SYNC writes implement true O_SYNC.	 WITHOUT this  option,
	      Linux  XFS  behaves  as if an osyncisdsync option is used, which
	      will make writes to files opened with the O_SYNC flag set behave
	      as  if  the O_DSYNC flag had been used instead.  This can result
	      in better performance without compromising data safety.  However
	      if  this	option is not in effect, timestamp updates from O_SYNC
	      writes can be lost if the system crashes.	 If timestamp  updates
	      are critical, use the osyncisosync option.

	      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.
	      If this option is not specified and the filesystem was made on a
	      stripe volume or the stripe width or unit were specified for the
	      RAID device at mkfs  time,  then	the  mount  system  call  will
	      restore the value from the superblock.  For filesystems that are
	      made directly on RAID devices, these  options  can  be  used  to
	      override	the  information  in  the superblock if the underlying
	      disk layout changes after the filesystem has been created.   The
	      swidth  option  is  required if the sunit option has been speci‐
	      fied, and must be a multiple of the sunit value.

	      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.

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/fdimage /mnt -t vfat -o loop=/dev/loop3

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

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

       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

       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 syntax of external mount helpers is:

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

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

       /etc/fstab	 filesystem table

       /etc/mtab	 table of mounted filesystems

       /etc/mtab~	 lock file

       /etc/mtab.tmp	 temporary file

       /etc/filesystems	 a list of filesystem types to try

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

       Mount  by  label	 or uuid will work only if your devices have the names
       listed in /proc/partitions.  In particular, it may  well	 fail  if  the
       kernel was compiled with devfs but devfs is not mounted.

       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

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

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

Linux 2.6			  2004-12-16			      MOUNT(8)

List of man pages available for Scientific

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