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MOUNT(8)		   Linux Programmer's Manual		      MOUNT(8)

NAME
       mount - mount a file system

SYNOPSIS
       mount [-lhV]

       mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
       mount [-fnrsvw] [-o options [,...]] device | dir
       mount [-fnrsvw] [-t vfstype] [-o options] device dir

DESCRIPTION
       All files accessible in a Unix system are arranged in one big tree, the
       file hierarchy, rooted at /.  These files can be spread out  over  sev‐
       eral  devices. The mount command serves to attach the file system 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 file system 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 file
       system remains mounted, the pathname dir refers to the root of the file
       system on device.

       Three forms of invocation do not actually mount anything:
	      mount -h
       prints a help message;
	      mount -V
       prints a version string; and just
	      mount [-l] [-t type]
       lists  all mounted file systems (of type type).	The option -l adds the
       (ext2, ext3, ext4 and XFS) labels in this listing.  See below.

       Since Linux 2.4.0 it is possible to remount part of the file  hierarchy
       somewhere else. The call is
	      mount --bind olddir newdir
       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  possible
       submounts.  The entire file hierarchy including submounts is attached a
       second place using
	      mount --rbind 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.

       All attribute changes (remount) to the bind mount will propagate to the
       source  mount. The read-only bind mounts are implemented in since Linux
       2.6.26.

       Since Linux 2.5.1 it is possible to atomically move a mounted  tree  to
       another place. The call is
	      mount --move olddir newdir

       Since  Linux 2.6.15 it is possible to mark a mount and its submounts 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 master, but any not vice-versa.  A private mount
       carries no propagation 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 proc file system 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.)

       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  file  /etc/fstab (see fstab(5)), may contain lines describing what
       devices are usually mounted where, using which options.	This  file  is
       used in three ways:

       (i) The command
	      mount -a [-t type] [-O optlist]
       (usually	 given	in  a bootscript) causes all file systems 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 con‐
       tains the noauto keyword. Adding the -F option will make mount fork, so
       that the filesystems are mounted simultaneously.

       (ii)  When  mounting  a	file system mentioned in fstab, it suffices to
       give only the device, or only the mount point.

       (iii) Normally, only the superuser can mount  file  systems.   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 file system found on his CDROM using the
       command
	      mount /dev/cdrom
       or
	      mount /cd
       For  more details, see fstab(5).	 Only the user that mounted a filesys‐
       tem 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 simi‐
       lar 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 programs mount and umount maintain a list of currently mounted file
       systems	in  the	 file  /etc/mtab.  If no arguments are given to mount,
       this list is printed.

       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  necessar‐
       ily  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 work‐
       ing  with the loop device will be less convenient, and using the "user"
       option will fail.

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

       Options available for the mount command:

       -V     Output version.

       -h     Print a help message.

       -v     Verbose mode.

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

       -F     (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     Causes  everything to be done except for the actual system call;
	      if it's not obvious, this ``fakes'' mounting  the	 file  system.
	      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.

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

       -l     Add  the	ext2,  ext3,  ext4 and XFS 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     Mount without writing in /etc/mtab.  This is necessary for exam‐
	      ple when /etc is on a read-only file system.

       -p 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     Mount the file system read-only. A synonym is -o ro.

       -w     Mount the file system 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 vfstype
	      The  argument following the -t is used to indicate the file sys‐
	      tem type.	 The file system types which are  currently  supported
	      include:	adfs,  affs,  autofs,  cifs,  coda,  coherent, cramfs,
	      debugfs, devpts, efs, ext, ext2, ext3, ext4, hfs, hpfs, iso9660,
	      jfs,  minix,  msdos,  ncpfs, nfs, nfs4, ntfs, proc, qnx4, ramfs,
	      reiserfs, romfs, smbfs, sysv, tmpfs, 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.

	      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  ad  hoc
	      code  is	built  in,  but cifs, smbfs, and ncpfs 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.	 If mount was compiled
	      with  the	 blkid	library, the guessing is done by this library.
	      Otherwise, mount guesses itself by probing  the  superblock;  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, nfs, and nfs4).  If /etc/filesystems ends
	      in a line with a single * only, mount will  read	/proc/filesys‐
	      tems 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
	      guess.

	      More than one type may be specified in a comma  separated	 list.
	      The list of file system types can be prefixed with no to specify
	      the file system 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 file systems except those of type msdos and ext.

       -O     Used  in conjunction with -a, to limit the set of filesystems to
	      which the -a is applied.	Like -t in this regard except that  it
	      is  useless  except in the context of -a.	 For example, the com‐
	      mand:
		     mount -a -O no_netdev
	      mounts all file systems except those which have the option _net‐
	      dev specified in the options field in the /etc/fstab file.

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

	      The  -t  and  -O	options are cumulative in effect; that is, the
	      command
		     mount -a -t ext2 -O _netdev
	      mounts all ext2 filesystems with the  _netdev  option,  not  all
	      filesystems  that	 are  either  ext2  or have the _netdev option
	      specified.

       -o     Options are specified with a -o flag followed by a  comma	 sepa‐
	      rated  string of options.	 Some of these options are only useful
	      when they appear in the /etc/fstab file.	The following  options
	      apply  to	 any  file system that is being mounted (but not every
	      file system 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 file system should be done asynchronously.

	      atime  Update  inode  access  time  for each access. This is the
		     default.

	      auto   Can be mounted with the -a option.

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

	      dev    Interpret	character or block special devices on the file
		     system.

	      exec   Permit execution of binaries.

	      group  Allow an ordinary (i.e., non-root) user to mount the file
		     system  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).

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

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

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

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

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

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

	      noexec Do not allow direct execution  of	any  binaries  on  the
		     mounted  file system.  (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.)

	      nomand Do not allow mandatory locks on this filesystem.

	      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.)

	      nouser Forbid an ordinary (i.e., non-root)  user	to  mount  the
		     file system.  This is the default.

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

	      remount
		     Attempt  to remount an already-mounted file system.  This
		     is commonly used to change the mount  flags  for  a  file
		     system,  especially to make a readonly file system write‐
		     able. It does not change device or mount point.

	      ro     Mount the file system read-only.

	      _rnetdev
		     Like _netdev, except "fsck	 -a"  checks  this  filesystem
		     during rc.sysinit.

	      rw     Mount the file system read-write.

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

	      sync   All I/O to the file system 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.

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

	      user   Allow an ordinary user to mount  the  file	 system.   The
		     name  of  the mounting user is written to mtab so that he
		     can unmount the file system again.	 This  option  implies
		     the  options noexec, nosuid, and nodev (unless overridden
		     by	 subsequent   options,	 as   in   the	 option	  line
		     user,exec,dev,suid).

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

	      context=context, fscontext=context and defcontext=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-sup‐
		     porting  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 context.

		     A commonly	 used  option  for  removable  media  is  con‐
		     text=system_u:object_r:removable_t.

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

		     The fscontext= option works for all filesystems,  regard‐
		     less  of  their  xattr support. The fscontext option sets
		     the overarching filesystem label to a  specific  security
		     context. This filesystem label is separate from the indi‐
		     vidual 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 unlabeled files in the policy and requires a file
		     system that supports xattr labeling.

		     For more details see selinux(8)

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

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

FILESYSTEM SPECIFIC MOUNT OPTIONS
       The following options apply only to certain file systems.  We sort them
       by file system. They all follow the -o flag.

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

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

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

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

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

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

       protect
	      Do not allow any changes to the protection bits on the file sys‐
	      tem.

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

       verbose
	      Print an informational message for each successful mount.

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

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

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

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

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

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

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

Mount options for cifs
       Just like nfs or smbfs implementation expects a binary argument to  the
       mount  system  call.  This argument is constructed by mount.cifs(8) and
       the current version of mount (2.12) does not know anything about cifs.

Mount options for coherent
       None.

Mount options for debugfs
       The debugfs file system is a pseudo file system, traditionally  mounted
       on /sys/kernel/debug.  There are no mount options.

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

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

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

Mount options for ext
       None.   Note  that  the	`ext'  file  system 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' file system is the standard Linux file system.  Since Linux
       2.5.46, for most	 mount	options	 the  default  is  determined  by  the
       filesystem superblock. Set them with tune2fs(8).

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

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

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

       (Note  that this example shows that one can add command line options to
       the options given in /etc/fstab.)

       check=none / nocheck
	      No checking is done at mount time. This is the default. This  is
	      fast.   It  is wise to invoke e2fsck(8) every now and then, e.g.
	      at boot time.

       debug  Print debugging info upon each (re)mount.

       errors=continue / errors=remount-ro / errors=panic
	      Define the behaviour when	 an  error  is	encountered.   (Either
	      ignore  errors  and just mark the file system erroneous and con‐
	      tinue, or remount the file system read-only, or panic  and  halt
	      the  system.)   The default is set in the filesystem superblock,
	      and can be changed using tune2fs(8).

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

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

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

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

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

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

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

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

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

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

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

       noload Do not load the ext3 file system's journal on mounting.

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

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

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

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

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

Mount options for ext4
       The  `ext4' is an an advanced level of the ext3 filesystem which incor‐
       porates 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.

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

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

       journal=update
	      Update the ext4 file system'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.

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

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

       delalloc
	      Deferring block allocation until write-out time.

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

       max_batch_time=usec
	      Maximum amount of time ext4 should wait for additional  filesys‐
	      tem  operations  to  be  batch together with a synchronous write
	      operation. Since a synchronous write operation is going to force
	      a	 commit	 and then a wait for the I/O complete, it doesn't cost
	      much, and can be a huge throughput win,  we  wait	 for  a	 small
	      amount of time to see if any other transactions can piggyback on
	      the synchronous write. The algorithm used is designed  to	 auto‐
	      matically	 tune  for  the	 speed	of  the disk, by measuring the
	      amount of time (on average) that it takes to finish committing a
	      transaction. Call this time the "commit time".  If the time that
	      the 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
	      0.

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

       journal_ioprio=prio
	      The  I/O	priority (from 0 to 7, where 0 is the highest 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.

       auto_da_alloc / noauto_da_alloc
	      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 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.

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

       blocksize=512 / blocksize=1024 / blocksize=2048
	      Set blocksize (default 512).

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

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

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

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

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

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

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

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

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

       conv=b[inary] / conv=t[ext] / conv=a[uto]
	      The fat file system 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 con‐
	      version.	Several people have had	 their	data  ruined  by  this
	      translation. Beware!

	      For  file	 systems  mounted  in  binary  mode, a conversion tool
	      (fromdos/todos) is available.

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

       cvf_option=option
	      Option passed to the CVF module.

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

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

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

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

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

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

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

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

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

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

       quiet  Don't complain about invalid mount options.

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

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

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

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

       nocheck
	      Do not abort mounting when certain consistency checks fail.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Mount options for minix
       None.

Mount options for msdos
       See  mount options for fat.  If the msdos file system detects an incon‐
       sistency, it reports an error and sets the file system  read-only.  The
       file system 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
       Instead of a textual option string, parsed by the kernel, the nfs  file
       system  expects	a  binary argument of type struct nfs_mount_data.  The
       program	mount  itself  parses  the  following  options	of  the	  form
       `tag=value',  and  puts	them  in  the  structure  mentioned:  rsize=n,
       wsize=n,	 timeo=n,  retrans=n,  acregmin=n,   acregmax=n,   acdirmin=n,
       acdirmax=n,  actimeo=n,	retry=n,  port=n, mountport=n, mounthost=name,
       mountprog=n, mountvers=n, nfsprog=n, nfsvers=n, namlen=n.   The	option
       addr=n  is  accepted  but ignored.  Also the following Boolean options,
       possibly preceded by no are  recognized:	 bg,  fg,  soft,  hard,	 intr,
       posix, cto, ac, tcp, udp, lock.	For details, see nfs(5).

       Especially useful options include

       rsize=32768,wsize=32768
	      This  causes the NFS client to try to negotiate a buffer size up
	      to the size specified.  A large buffer size does improve perfor‐
	      mance,  but  both	 the server and client have to support it.  In
	      the case where one of these does not support the size specified,
	      the size negotiated will be the largest that both support.

       intr   This  will  allow	 NFS  operations (on hard mounts) to be inter‐
	      rupted while waiting for a response from the server.

       nolock Do not use locking. Do not start lockd.

Mount options for nfs4
       Instead of a textual option string, parsed by the kernel, the nfs4 file
       system  expects	a binary argument of type struct nfs4_mount_data.  The
       program	mount  itself  parses  the  following  options	of  the	  form
       `tag=value',  and  puts	them  in  the  structure  mentioned:  rsize=n,
       wsize=n,	 timeo=n,  retrans=n,  acregmin=n,   acregmax=n,   acdirmin=n,
       acdirmax=n,  actimeo=n,	retry=n, port=n, proto=n, clientaddr=n, sec=n.
       The option addr=n is accepted but ignored.  Also the following  Boolean
       options,	 possibly  preceded  by no are recognized: bg, fg, soft, hard,
       intr, cto, ac, For details, see nfs(5).

       Especially useful options include

       rsize=32768,wsize=32768
	      This causes the NFS4 client to try to negotiate a buffer size up
	      to the size specified.  A large buffer size does improve perfor‐
	      mance, but both the server and client have to  support  it.   In
	      the case where one of these does not support the size specified,
	      the size negotiated will be the largest that both support.

       intr   This will allow NFS4 operations (on hard mounts)	to  be	inter‐
	      rupted while waiting for a response from the server.

Mount options for ntfs
       iocharset=name
	      Character	 set  to  use when returning file names.  Unlike VFAT,
	      NTFS suppresses names  that  contain  unconvertible  characters.
	      Deprecated.

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

       utf8   Use UTF-8 for converting file names.

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

       posix=[0|1]
	      If  enabled  (posix=1),  the  file  system distinguishes between
	      upper and lower case. The 8.3 alias names are presented as  hard
	      links instead of being suppressed.

       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.  The reiserfs  mount  options  are
       more fully described at http://www.namesys.com/mount-options.html.

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

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

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

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

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

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

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

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

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

       nolog  Disable  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.

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

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

Mount options for romfs
       None.

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

Mount options for sysv
       None.

Mount options for tmpfs
       The  following  parameters  accept  a  suffix  k, m or g for Ki, Mi, Gi
       (binary kilo, mega and giga) and can be changed on remount.

       size=nbytes
	      Override default maximum size of the filesystem.	 The  size  is
	      given  in	 bytes, and rounded down to entire pages.  The default
	      is half of the memory.

       nr_blocks=
	      Set number of blocks.

       nr_inodes=
	      Set number of inodes.

       mode=  Set initial permissions of the root directory.

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

       undelete
	      Show deleted files in lists.

       nostrict
	      Unset strict conformance.

       iocharset
	      Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

       anchor=
	      Override standard anchor location. Default: 256.

       volume=
	      Override the VolumeDesc location. (unused)

       partition=
	      Override the PartitionDesc location. (unused)

       lastblock=
	      Set the last block of the filesystem.

       fileset=
	      Override the fileset block location. (unused)

       rootdir=
	      Override the root directory location. (unused)

Mount options for ufs
       ufstype=value
	      UFS is a file system 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‐
		     BSD,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.

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

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

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

       onerror=value
	      Set behaviour on error:

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

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

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

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

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

       posix  Allow two files with names that only differ in case.

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

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

       shortname=[lower|win95|winnt|mixed]

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

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

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

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

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

       The default is "lower".

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  file  system (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  file  system (default: uid=gid=0, mode=0555). The mode is
	      given in octal.

       listuid=uid and listgid=gid and listmode=mode
	      Set the owner and group and mode of the file  devices  (default:
	      uid=gid=0, mode=0444). The mode is given in octal.

Mount options for xenix
       None.

Mount options for xfs
       allocsize=size
	      Sets  the buffered I/O end-of-file preallocation size when doing
	      delayed allocation writeout (default size is 64KiB).  Valid val‐
	      ues  for	this  option are page size (typically 4KiB) through to
	      1GiB, inclusive, in power-of-2 increments.

       attr2 / noattr2
	      The options enable/disable (default  is  disabled	 for  backward
	      compatibility on-disk) 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.

       barrier
	      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.

       ihashsize=value
	      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.

       ikeep / noikeep
	      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.

       inode64
	      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.

       largeio / nolargeio
	      If nolargeio is specified, the optimal I/O reported  in  st_blk‐
	      size  by	stat(2)	 will  be  as  small as possible to allow user
	      applications to avoid  inefficient  read/modify/write  I/O.   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.

       logbufs=value
	      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.

       logbsize=value
	      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).

       mtpt=mountpoint
	      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.

       noalign
	      Data allocations will not be aligned at stripe unit boundaries.

       noatime
	      Access timestamps are not updated when a file is read.

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

       nouuid Don't check for double mounted file systems using the file  sys‐
	      tem uuid.	 This is useful to mount LVM snapshot volumes.

       osyncisdsync
	      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.

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

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

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

       sunit=value and swidth=value
	      Used to specify the stripe unit and width for a RAID device or a
	      stripe volume.  value must be specified in 512-byte block units.
	      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.

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

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

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

	 mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024

       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 three options, namely loop, offset and
       encryption, that are really options to losetup(8).  (These options  can
       be used in addition to those specific to the filesystem type.)

       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.  If you are not so unwise as to make /etc/mtab a symbolic link to
       /proc/mounts then any loop device allocated by mount will be  freed  by
       umount.	 You  can also free a loop device by hand, using `losetup -d',
       see losetup(8).

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

       0      success

       1      incorrect invocation or permissions

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

       4      internal mount bug or missing nfs support in mount

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

FILES
       /etc/fstab	 file system table

       /etc/mtab	 table of mounted file systems

       /etc/mtab~	 lock file

       /etc/mtab.tmp	 temporary file

       /etc/filesystems	 a list of filesystem types to try

SEE ALSO
       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)

BUGS
       It is possible for a corrupted file system to cause a crash.

       Some Linux file systems don't support -o sync and -o dirsync (the ext2,
       ext3,  fat  and	vfat file systems 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
       used.

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

Linux 2.6			  2004-12-16			      MOUNT(8)
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