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Linux 2.6 - man page for mount (linux section 8)

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 several 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 invis-
       ible, 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 knuth.cwi.nl:/dir.  It is possible to indicate a  block
	      special device using its volume LABEL or UUID (see the -L and -U options below).

	      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 portable. 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).

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

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

       The /etc/fstab, /etc/mtab and /proc/mounts files.
	      The file /etc/fstab (see fstab(5)), may contain lines describing what  devices  are
	      usually mounted where, using which options.

	      The 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  indi-
	      cated,  except  for  those  whose  line  contains the noauto keyword. Adding the -F
	      option will make mount fork, so that the filesystems are mounted simultaneously.

	      When mounting a filesystem mentioned in fstab or mtab, it suffices 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 former 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 sub-
	      mounts. The entire file hierarchy including submounts is attached  a  second  place

		     mount --rbind olddir newdir

	      or shortoption

		     mount -R olddir newdir

	      Note  that the filesystem mount options will remain the same as those on the origi-
	      nal 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

		     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

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

       The shared subtrees operations.
	      Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, pri-
	      vate,  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 master, but any not vice-
	      versa.  A private mount carries no propagation abilities.  A unbindable mount is	a
	      private  mount  which cannot be 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 determined 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

       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 paral-
	      lel. A disadvantage is that the mounts are done in undefined order.  Thus, you can-
	      not 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  obvi-
	      ous,  this ``fakes'' mounting the filesystem.  This option is useful in conjunction
	      with the -v flag to determine what the mount command is trying to do. It	can  also
	      be  used	to  add entries for devices that were mounted earlier with the -n option.
	      The -f option checks for existing record in /etc/mtab and  fails	when  the  record
	      already exists (with regular non-fake mount, this check is done by kernel).

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

       -l     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
	      reiserfs using reiserfstune(8).

       -n, --no-mtab
	      Mount without writing in /etc/mtab.  This is necessary for example 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,  reis-
	      erfs,  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 kernel.

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

	      For  most  types	all the mount program has to do is issue a simple mount(2) system
	      call, and no detailed knowledge of the filesystem 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  program.  In
	      order  to  make it possible to treat all types in a uniform 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/filesys-
	      tems.  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.

	      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  exam-
	      ple, 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 command:

		     mount -a -O no_netdev

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

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

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

		     mount -a -t ext2 -O _netdev

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

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

		     mount LABEL=mydisk -o noatime,nouser

	      MOUNT OPTIONS sections.

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

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

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

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

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

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

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

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

	      A commonly used option  for  removable  media  is  context=system_u:object_r:remov-

	      Two other options are fscontext= and defcontext=, both of which are mutually exclu-
	      sive 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 themselves. The context option actually sets the aggregate con-
	      text  that fscontext provides, in addition to supplying the same label for individ-
	      ual files.

	      You can set the default security context	for  unlabeled	files  using  defcontext=
	      option. This overrides the value set for unlabeled files in the policy and requires
	      a filesystem that supports xattr labeling.

	      The rootcontext= option allows you to explicitly label the root inode of a FS being
	      mounted  before that FS or inode because visable to userspace. This was found to be
	      useful for things like stateless linux.

	      Note that kernel rejects any remount request that includes the context option  even
	      if unchanged from the current context.

	      For more details, see selinux(8)

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

       dev    Interpret character or block special devices on the filesystem.

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

	      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 synchronously.  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

	      Specifies an encryption algorithm to  use.   Used  in  conjunction  with	the  loop

	      Specifies the key size to use for an encryption algorithm. Used in conjunction with
	      the loop and encryption options.	nofail Do not report errors for this device if it
	      does  not  exist.   iversion  Every time the inode is modified, the i_version field
	      will be incremented.

	      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 earlier than the current modify or change
	      time. (Similar to noatime, but doesn't break mutt or other applications  that  need
	      to know if a file has been read since the last time it was modified.)

	      Since  Linux  2.6.30,  the  kernel defaults to the behavior provided by this option
	      (unless noatime was  specified), and the strictatime 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 option.

	      Allows to explicitly requesting full atime updates. This makes it possible for ker-
	      nel  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 updates.

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

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

       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 commonly used to change
	      the mount flags  for  a  filesystem,  especially	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 command 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  lim-
	      ited  number  of	write cycles (e.g. some flash drives) "sync" may cause life-cycle

       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 filesystem.  This is the

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

       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 Documentation/filesystems.

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

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

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  original  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 filesystem.

       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 device.

	      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 utilities 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	package  must  be

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

	      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 imple-
	      mented in linux kernel versions starting with 2.6.29.  Further, this  mount  option
	      is valid only if CONFIG_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 filesystem.

	      With  the  support for multiple instances of devpts (see newinstance option above),
	      each instance has a private ptmx node in the root of the devpts  filesystem  (typi-
	      cally /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 starting with 2.6.29. Fur-
	      ther this option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES  is  enabled  in
	      the kernel configuration.

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

	      Support POSIX Access Control Lists (or not).

	      Set the behaviour for the statfs system call. The minixdf behaviour 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 continue, 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 default.

       resgid=n and resuid=n
	      The  ext2  filesystem  reserves  a  certain  percentage  of the available 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 speci-
	      fied group.)

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

	      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 jour-
       nalling.  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. Otherwise, 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 identi-
	      fied 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 incon-
	      sistencies 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.  rootflags=data=journal.

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

		     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  filesys-
		     tem  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,  barrier=1  enables  it.
	      Write  barriers enforce proper on-disk ordering 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 barriers unless your
	      disks are battery-backed one way or another.  Otherwise you risk filesystem corrup-
	      tion 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 supporting large filesystem.

       The  options  journal_dev,  noload, data, commit, orlov, oldalloc, [no]user_xattr [no]acl,
       bsddf, minixdf, debug, errors, data_err, grpid,	bsdgroups,  nogrpid  sysvgroups,  resgid,
       resuid,	sb,  quota, noquota, grpquota, usrquota and [no]bh 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 corruption 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  descriptor  blocks.  If
	      enabled  older kernels cannot mount the device. This will enable 'journal_checksum'

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

	      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 filesystem operations to  be
	      batch together with a synchronous write operation. Since a synchronous write opera-
	      tion 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 automatically tune for the speed of the disk, by measuring the
	      amount of time (on average) that it takes to finish committing a transaction.  Call
	      this  time the "commit time".  If the time that the transaction has been running is
	      less than the commit time, ext4 will try sleeping for the commit	time  to  see  if
	      other  operations  will  join  the  transaction.	The  commit time is capped by the
	      max_batch_time, which defaults to 15000us (15ms). 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 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 purposes.  This is  nor-
	      mally 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("foo.new")/write(fd,..)/close(fd)/ rename("foo.new", "foo")

	      or worse yet

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

	      If auto_da_alloc is enabled, ext4 will detect the replace-via-rename  and  replace-
	      via-truncate  patterns  and  force that any delayed allocation blocks are allocated
	      such that at the next journal commit, in the default data=ordered  mode,	the  data
	      blocks  of the new file are forced to disk before the rename() operation is commit-
	      ted.  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 remount.

	      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 routines to quickly locate extents which might overlap
	      with filesystem metadata blocks. This option is intended for debugging purposes and
	      since it negatively affects the performance, it is off by default.

	      Controls whether or not ext4 should use the DIO read locking. If the dioread_nolock
	      option is specified ext4 will allocate uninitialized extent before buffer write and
	      convert  the  extent  to initialized after IO completes.	This approach allows ext4
	      code to avoid using inode mutex, which improves scalability on high speed storages.
	      However  this  does  not work with 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.

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

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

	      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

	      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 cur-
	      rent 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 trun-
		     cated (e.g.  verylongname.foobar becomes verylong.foo), leading and embedded
		     spaces are accepted in each name part (name and extension).

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

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

	      Sets the codepage for converting to shortname characters on FAT and  VFAT  filesys-
	      tems. 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 conversion modes are available:

	      binary no translation is performed.  This is the default.

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

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

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

	      For filesystems mounted in binary mode, a conversion tool (fromdos/todos) is avail-
	      able. 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 con-
	      trols on-demand CVF module 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 filesystem parameters will
	      be printed (these data are also printed if the parameters appear	to  be	inconsis-

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

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

       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  exten-
	      sion 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

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

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

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

       quiet  Don't complain about invalid mount options.

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

	      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: case=lower.)

	      For  conv=text,  delete  some  random  CRs (in particular, all followed 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

	      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 filesystem (except that it is read-only, of course).

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

	      Disable the use of Microsoft Joliet extensions, even if available. 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  overrid-
	      ing 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 per-
	      mission 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 inacces-

	      Set the block size to the indicated value.  (Default: block=1024.)

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

       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 extensions.

	      Character  set to use for converting 16 bit Unicode characters on CD to 8 bit char-
	      acters. 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  CON-
	      FIG_NLS_UTF8 to be set in the kernel .config file.

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

	      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 previously 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 continue, 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 inconsistency, 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 constructed 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-common 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. Deprecated.

	      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 charac-
	      ters.   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  bigen-
	      dian encoding.

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

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

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

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

Mount options for reiserfs
       Reiserfs is a journaling filesystem.

       conv   Instructs  version  3.6  reiserfs software to mount a version 3.5 filesystem, using
	      the 3.6 format for newly created objects. This filesystem will no longer be compat-
	      ible 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 preserves locality,
		     mapping lexicographically close file  names  to  close  hash  values.   This
		     option  should  not  be used, as it causes a high probability of hash colli-

	      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 EHASH-
		     COLLISION 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

	      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 improvements in some situa-

	      Tunes the block allocator. This may provide performance improvements in some situa-

	      Disable the border allocator algorithm invented by Yury Yu. Rupasov.  This may pro-
	      vide performance improvements in some situations.

       nolog  Disable journalling. This will provide slight performance improvements in some sit-
	      uations 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

       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 pack-
	      ing 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 partitions.	Instructs
	      reiserfs	to assume that the device has number blocks.  This option is designed for
	      use with devices which are under logical volume management (LVM).  There is a  spe-
	      cial  resizer utility which can be obtained from ftp://ftp.namesys.com/pub/reiserf-

	      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  journaling  code.   bar-
	      rier=none  disables it, barrier=flush enables it. Write barriers enforce proper on-
	      disk ordering of journal commits, 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 constructed 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

	      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 lower.

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

       mode=  Set initial permissions of the root directory.

       uid=   The user id.

       gid=   The group id.

	      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 example, mpol=bind:0-3,5,7,9-15

	      Note that trying to mount a tmpfs with an mpol option will fail if the running ker-
	      nel  does not support NUMA; and will fail if its nodelist specifies a node which is
	      not online.  If your system 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 advisable to omit the mpol option from auto-
	      matic  mount  options.  It can be added later, when the tmpfs is already mounted on
	      MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.

Mount options for ubifs
       UBIFS is a flash file system which works on top of UBI volumes. Note  that  atime  is  not
       supported and is always turned off.

       The device name may be specified as
	      ubiX_Y UBI device number X, volume number Y

	      ubiY   UBI device number 0, volume number Y

		     UBI device number X, volume with name NAME

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

       The following mount options are available:

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

	      Do not bulk-read. This is the default.

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

	      Do not check data CRC-32 checksums. With this option, the filesystem does not check
	      CRC-32  checksum	for data, but it does check it for the internal indexing informa-
	      tion. 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  undocu-
	      mented,  so  its	hard  to recognize the type of ufs automatically.  That's why the
	      user must specify the type of ufs by mount option.  Possible values are:

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

	      44bsd  For filesystems created by a BSD-like system (NetBSD,FreeBSD,OpenBSD).

	      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 X.

	      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  encoun-
		     tered only a console message is printed.

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

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

	      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 character, 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.

	      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 64KiB).  Valid values for this option are page size (typ-
	      ically 4KiB) through to 1GiB, inclusive, in power-of-2 increments.

	      The options enable/disable (default is enabled) 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 (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 support 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_blksize by stat(2) will
	      be as small as possible to allow user applications to avoid  inefficient	read/mod-
	      ify/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 any recent kernel.

	      Set the size of each in-memory log buffer.  Size may be specified in bytes,  or  in
	      kilobytes  with  a  "k"  suffix.	 Valid sizes for version 1 and version 2 logs are
	      16384 (16k) and 32768 (32k).  Valid sizes for version 2  logs  also  include  65536
	      (64k), 131072 (128k) and 262144 (256k).  The default value for any recent kernel is

       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
	      section 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.	 Filesys-
	      tems mounted norecovery must be mounted read-only or the mount will fail.

       nouuid Don't check for double mounted filesystems using the filesystem uuid.  This is use-
	      ful 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 specified, 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/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,  sizelimit  and  encryp-
       tion, that are really options to losetup(8).  If the mount requires a passphrase, you will
       be prompted for one unless you specify a file descriptor to read  from  instead	with  the
       --pass-fd  option.   (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 independently on /etc/mtab.

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

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

       0      success

       1      incorrect invocation or permissions

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

       4      internal mount bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

       The syntax of external mount helpers is:

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

       where  the  <type>  is  filesystem type and -sfnvo options have same meaning 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), 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).

       Mount  by label or uuid will work only if your devices have the names listed in /proc/par-
       titions.  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  usu-
       ally contains more reliable information.)

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

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

       The  mount  command is part of the util-linux package and is available from ftp://ftp.ker-

Linux 2.6				    2004-12-16					 MOUNT(8)

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