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


           All files accessible in a Unix system are arranged in one big tree, the
           file hierarchy, rooted at /.  These files can be spread out  over  sev-
           eral  devices.  The mount command serves to attach the filesystem found
           on some device to the big file tree. Conversely, the umount(8)  command
           will detach it again.
           The standard form of the mount command, is
                  mount -t type device dir
           This  tells  the kernel to attach the filesystem found on device (which
           is of type type) at the directory dir.  The previous contents (if  any)
           and  owner  and  mode  of  dir  become  invisible,  and as long as this
           filesystem remains mounted, the pathname dir refers to the root of  the
           filesystem on device.
           The listing and help.
                  Three forms of invocation do not actually mount anything:
                  mount -h
                         prints a help message
                  mount -V
                         prints a version string
                  mount [-l] [-t type]
                         lists all mounted filesystems (of type type).  The option
                         -l adds the labels in this listing.  See below.
           The device indication.
                  Most devices are indicated by a file name (of  a  block  special
                  device),  like /dev/sda1, but there are other possibilities. For
                  example, in the case of an  NFS  mount,  device  may  look  like
           It  is possible to indicate a block special
                  device using its volume LABEL or UUID (see the -L and -U options
                  The  recommended  setup  is  to use LABEL=<label> or UUID=<uuid>
                  tags rather than /dev/disk/by-{label,uuid} udev symlinks in  the
                  /etc/fstab   file.  The  tags  are  more  readable,  robust  and
                  portable. The mount(8) command internally uses udev symlinks, so
                  use   the   symlinks   in   /etc/fstab  is  not  advantage  over
                         mount -a [-t type] [-O optlist]
                  (usually given in a bootscript) causes all filesystems mentioned
                  in fstab (of the proper type and/or having  or  not  having  the
                  proper  options)  to  be  mounted as indicated, except for those
                  whose line contains the noauto keyword.  Adding  the  -F  option
                  will make mount fork, so that the filesystems are mounted simul-
                  When mounting a filesystem mentioned in fstab or mtab,  it  suf-
                  fices to give only the device, or only the mount point.
                  The  programs  mount  and  umount  maintain  a list of currently
                  mounted filesystems in the file /etc/mtab.  If no arguments  are
                  given to mount, this list is printed.
                  The  mount  program  does not read the /etc/fstab file if device
                  (or LABEL/UUID) and dir are specified. For example:
                         mount /dev/foo /dir
                  If you want to override mount options from /etc/fstab  you  have
                  to use:
                         mount device|dir -o <options>
                  and then the mount options from command line will be appended to
                  the list of options from /etc/fstab.   The  usual  behaviour  is
                  that the last option wins if there is more duplicated options.
                  When  the  proc  filesystem is mounted (say at /proc), the files
                  /etc/mtab and /proc/mounts have very similar contents. The  for-
                  mer  has  somewhat  more  information, such as the mount options
                  used, but is not  necessarily  up-to-date  (cf.  the  -n  option
                  below).  It  is possible to replace /etc/mtab by a symbolic link
                  to /proc/mounts, and especially when you have very large numbers
                  of mounts things will be much faster with that symlink, but some
                  information is lost that way, and in particular using the "user"
                  option will fail.
           The non-superuser mounts.
                  Normally,  only  the  superuser can mount filesystems.  However,
                  when fstab contains the user option on a line, anybody can mount
                  the corresponding system.
                  Thus, given a line
                         /dev/cdrom  /cd  iso9660  ro,user,noauto,unhide
                  any  user  can  mount  the iso9660 filesystem found on his CDROM
                  using the command
                  restriction  that  the  user  must be member of the group of the
                  special file.
           The bind mounts.
                  Since Linux 2.4.0 it is possible to remount  part  of  the  file
                  hierarchy somewhere else. The call is
                         mount --bind olddir newdir
                  or shortoption
                         mount -B olddir newdir
                  or fstab entry is:
                         /olddir /newdir none bind
                  After  this  call the same contents is accessible in two places.
                  One can also remount a single file (on a single file).
                  This call attaches only (part of) a single filesystem, not  pos-
                  sible  submounts.  The entire file hierarchy including submounts
                  is attached a second place using
                         mount --rbind olddir newdir
                  or shortoption
                         mount -R olddir newdir
                  Note that the filesystem mount options will remain the  same  as
                  those  on  the  original  mount  point, and cannot be changed by
                  passing the -o  option  along  with  --bind/--rbind.  The  mount
                  options  can be changed by a separate remount command, for exam-
                         mount --bind olddir newdir
                         mount -o remount,ro newdir
           The move operation.
                  Since Linux 2.5.1 it is possible to atomically  move  a  mounted
                  tree to another place. The call is
                         mount --move olddir newdir
                  or shortoption
                         mount -M olddir newdir
                  This  will  cause  the  contents which previously appeared under
                  olddir to be accessed under newdir.  The  physical  location  of
                  the files is not changed.
           The shared subtrees operations.
                  Since  Linux  2.6.15 it is possible to mark a mount and its sub-
                  mounts as shared, private, slave or unbindable. A  shared  mount
                  provides  ability  to  create  mirrors  of  that mount such that
                  mounts and umounts within any of the mirrors  propagate  to  the
                  other  mirror.  A slave mount receives propagation from its mas-
                  ter, but any not vice-versa.  A private mount carries no  propa-
                  gation  abilities.   A unbindable mount is a private mount which
                  cannot cloned through a bind operation.  Detailed  semantics  is
                         mount --make-runbindable mountpoint


           The  full set of mount options used by an invocation of mount is deter-
           mined by first extracting the mount options for the filesystem from the
           fstab  table,  then  applying any options specified by the -o argument,
           and finally applying a -r or -w option, when present.
           Command line options available for the mount command:
           -V, --version
                  Output version.
           -h, --help
                  Print a help message.
           -v, --verbose
                  Verbose mode.
           -a, --all
                  Mount all filesystems (of the given types) mentioned in fstab.
           -F, --fork
                  (Used in conjunction with -a.)  Fork off a  new  incarnation  of
                  mount  for  each  device.   This will do the mounts on different
                  devices or different NFS servers  in  parallel.   This  has  the
                  advantage that it is faster; also NFS timeouts go in parallel. A
                  disadvantage is that the mounts are  done  in  undefined  order.
                  Thus,  you cannot use this option if you want to mount both /usr
                  and /usr/spool.
           -f, --fake
                  Causes everything to be done except for the actual system  call;
                  if  it's  not  obvious,  this ''fakes'' mounting the filesystem.
                  This option is useful in conjunction with the -v flag to  deter-
                  mine what the mount command is trying to do. It can also be used
                  to add entries for devices that were mounted earlier with the -n
                  option.  The  -f  option checks for existing record in /etc/mtab
                  and fails when the record already exists (with regular  non-fake
                  mount, this check is done by kernel).
           -i, --internal-only
                  Don't  call  the  /sbin/mount.<filesystem>  helper  even  if  it
           -l     Add the labels in the mount output. Mount must  have  permission
                  to  read  the  disk device (e.g. be suid root) for this to work.
                  One can set such a label  for  ext2,  ext3  or  ext4  using  the
                  e2label(8)  utility, or for XFS using xfs_admin(8), or for reis-
                  erfs using reiserfstune(8).
           -s     Tolerate  sloppy  mount  options  rather than failing. This will
                  ignore mount options not supported by a filesystem type. Not all
                  filesystems  support this option. This option exists for support
                  of the Linux autofs-based automounter.
           -r, --read-only
                  Mount the filesystem read-only. A synonym is -o ro.
                  Note that, depending on the filesystem type,  state  and  kernel
                  behavior, the system may still write to the device. For example,
                  Ext3 or ext4 will replay its journal if the filesystem is dirty.
                  To prevent this kind of write access, you may want to mount ext3
                  or ext4 filesystem with "ro,noload" mount  options  or  set  the
                  block device to read-only mode, see command blockdev(8).
           -w, --rw
                  Mount  the filesystem read/write. This is the default. A synonym
                  is -o rw.
           -L label
                  Mount the partition that has the specified label.
           -U uuid
                  Mount the partition that has  the  specified  uuid.   These  two
                  options  require  the file /proc/partitions (present since Linux
                  2.1.116) to exist.
           -t, --types vfstype
                  The argument following the -t is used to indicate the filesystem
                  type.   The  filesystem  types  which  are  currently  supported
                  include: adfs,  affs,  autofs,  cifs,  coda,  coherent,  cramfs,
                  debugfs, devpts, efs, ext, ext2, ext3, ext4, hfs, hfsplus, hpfs,
                  iso9660, jfs, minix, msdos, ncpfs, nfs, nfs4, ntfs, proc,  qnx4,
                  ramfs,  reiserfs,  romfs,  squashfs,  smbfs, sysv, tmpfs, ubifs,
                  udf, ufs, umsdos, usbfs, vfat, xenix,  xfs,  xiafs.   Note  that
                  coherent,  sysv  and  xenix  are  equivalent  and that xenix and
                  coherent will be removed at some point in the future -- use  sysv
                  instead.  Since kernel version 2.1.21 the types ext and xiafs do
                  not exist anymore. Earlier, usbfs was known as usbdevfs.   Note,
                  the  real list of all supported filesystems depends on your ker-
                  The programs mount and umount support filesystem subtypes.   The
                  subtype   is   defined   by   '.subtype'  suffix.   For  example
                  'fuse.sshfs'. It's recommended to use  subtype  notation  rather
                  than   add   any   prefix  to  the  mount  source  (for  example
                  '' is depreacated).
                  For most types all the mount program has to do is issue a simple
                  mount(2)  system call, and no detailed knowledge of the filesys-
                  tem type is required.  For a few types however (like nfs,  nfs4,
                  cifs,  smbfs,  ncpfs)  ad  hoc code is necessary. The nfs, nfs4,
                  will be tried, except for those that are labeled "nodev"  (e.g.,
                  devpts,  proc and nfs).  If /etc/filesystems ends in a line with
                  a single * only, mount will read /proc/filesystems afterwards.
                  The auto type may be useful for user-mounted floppies.  Creating
                  a  file /etc/filesystems can be useful to change the probe order
                  (e.g., to try vfat before msdos or ext3 before ext2) or  if  you
                  use  a  kernel  module  autoloader.  Warning: the probing uses a
                  heuristic (the presence of appropriate 'magic'), and could  rec-
                  ognize  the  wrong  filesystem  type, possibly with catastrophic
                  consequences. If your data  is  valuable,  don't  ask  mount  to
                  More  than  one type may be specified in a comma separated list.
                  The list of filesystem types can be prefixed with no to  specify
                  the  filesystem types on which no action should be taken.  (This
                  can be meaningful with the -a option.) For example, the command:
                         mount -a -t nomsdos,ext
                  mounts all filesystems except those of type msdos and ext.
           -O, --test-opts opts
                  Used  in conjunction with -a, to limit the set of filesystems to
                  which the -a is applied.  Like -t in this regard except that  it
                  is  useless  except in the context of -a.  For example, the com-
                         mount -a -O no_netdev
                  mounts all filesystems except those which have the option  _net-
                  dev specified in the options field in the /etc/fstab file.
                  It  is different from -t in that each option is matched exactly;
                  a leading no at the beginning of one option does not negate  the
                  The  -t  and  -O  options are cumulative in effect; that is, the
                         mount -a -t ext2 -O _netdev
                  mounts all ext2 filesystems with the  _netdev  option,  not  all
                  filesystems  that  are  either  ext2  or have the _netdev option
           -o, --options opts
                  Options are specified with a -o flag followed by a  comma  sepa-
                  rated string of options. For example:
                         mount LABEL=mydisk -o noatime,nouser


           Some of  these  options  are  only  useful  when  they  appear  in  the
           /etc/fstab file.
           Some  of  these  options could be enabled or disabled by default in the
           system kernel.  To  check  the  current  setting  see  the  options  in
           /proc/mounts.  Note  that filesystems also have per-filesystem specific
           default mount options (see for  example  tune2fs  -l  output  for  extN
           The  following  options  apply  to any filesystem that is being mounted
           (but not every filesystem actually honors them - e.g., the sync  option
           today has effect only for ext2, ext3, fat, vfat and ufs):
           async  All  I/O  to  the filesystem should be done asynchronously. (See
                  also the sync option.)
           atime  Do not use noatime feature, then the inode access time  is  con-
                  trolled  by kernel defaults. See also the description for stric-
                  tatime and relatime mount options.
                  Do not update inode access times on this  filesystem  (e.g,  for
                  faster access on the news spool to speed up news servers).
           auto   Can be mounted with the -a option.
           noauto Can  only  be  mounted  explicitly (i.e., the -a option will not
                  cause the filesystem to be mounted).
           context=context,  fscontext=context,  defcontext=context  and  rootcon-
                  The context= option is useful when mounting filesystems that  do
                  not  support  extended attributes, such as a floppy or hard disk
                  formatted with VFAT, or systems that are  not  normally  running
                  under SELinux, such as an ext3 formatted disk from a non-SELinux
                  workstation. You can also use context= on filesystems you do not
                  trust,  such  as  a  floppy. It also helps in compatibility with
                  xattr-supporting filesystems on earlier 2.4.<x> kernel versions.
                  Even where xattrs are supported, you can save time not having to
                  label every file by assigning the entire disk one security  con-
                  A  commonly  used  option  for  removable  media is context=sys-
                  Two other options are fscontext= and defcontext=, both of  which
                  are mutually exclusive of the context option. This means you can
                  use fscontext and defcontext with each other, but neither can be
                  using defcontext= option. This overrides the value set for unla-
                  beled files in the policy and requires a  filesystem  that  sup-
                  ports xattr labeling.
                  The  rootcontext= option allows you to explicitly label the root
                  inode of a FS being mounted before that FS or inode because vis-
                  able  to  userspace. This was found to be useful for things like
                  stateless linux.
                  For more details, see selinux(8)
                  Use default options: rw, suid, dev, exec, auto,  nouser,  async,
                  and relatime.
                  Note  that the real set of the all default mount options depends
                  on kernel and filesystem type. See the begin of this section for
                  more details.
           dev    Interpret  character or block special devices on the filesystem.
           nodev  Do not interpret character or block special devices on the  file
                  Update  directory inode access times on this filesystem. This is
                  the default.
                  Do not update directory inode access times on this filesystem.
                  All directory updates within the filesystem should be done  syn-
                  chronously.   This  affects  the  following system calls: creat,
                  link, unlink, symlink, mkdir, rmdir, mknod and rename.
           exec   Permit execution of binaries.
           noexec Do not allow direct execution of any  binaries  on  the  mounted
                  filesystem.   (Until  recently  it  was possible to run binaries
                  anyway using a command like /lib/ld*.so /mnt/binary. This  trick
                  fails since Linux 2.4.25 / 2.6.0.)
           group  Allow  an ordinary (i.e., non-root) user to mount the filesystem
                  if one of his groups matches the  group  of  the  device.   This
                  option  implies  the options nosuid and nodev (unless overridden
                  by subsequent options, as in the option line group,dev,suid).
                  Every time the inode is modified, the i_version  field  will  be
                  Update  inode  access  times  relative to modify or change time.
                  Access time is only updated if the previous access time was ear-
                  lier  than  the current modify or change time. (Similar to noat-
                  ime, but doesn't break mutt or other applications that  need  to
                  know  if  a  file has been read since the last time it was modi-
                  Since Linux 2.6.30, the kernel defaults to the behavior provided
                  by this option (unless noatime was  specified), and the stricta-
                  time option is required  to  obtain  traditional  semantics.  In
                  addition,  since  Linux  2.6.30,  the file's last access time is
                  always  updated  if  it  is more than 1 day old.
                  Do not use relatime feature.  See  also  the  strictatime  mount
                  Allows  to  explicitly requesting full atime updates. This makes
                  it possible for kernel to defaults to relatime  or  noatime  but
                  still allow userspace to override it. For more details about the
                  default system mount options see /proc/mounts.
                  Use  the  kernel's  default  behaviour  for  inode  access  time
           suid   Allow  set-user-identifier  or set-group-identifier bits to take
           nosuid Do not allow set-user-identifier or set-group-identifier bits to
                  take  effect.  (This seems safe, but is in fact rather unsafe if
                  you have suidperl(1) installed.)
           owner  Allow an ordinary (i.e., non-root) user to mount the  filesystem
                  if  he  is  the  owner  of  the device.  This option implies the
                  options  nosuid  and  nodev  (unless  overridden  by  subsequent
                  options, as in the option line owner,dev,suid).
                  Attempt  to remount an already-mounted filesystem.  This is com-
                  monly used to change the mount flags  for  a  filesystem,  espe-
                  cially  to  make  a  readonly  filesystem writeable. It does not
                  change device or mount point.
                  The remount functionality follows the standard way how the mount
                  command  works  with options from fstab. It means the mount com-
                  mand doesn't read fstab (or mtab) only when a device and dir are
                  fully specified.
                  Like _netdev, except "fsck -a"  checks  this  filesystem  during
           rw     Mount the filesystem read-write.
           sync   All  I/O to the filesystem should be done synchronously. In case
                  of media with limited number of write cycles  (e.g.  some  flash
                  drives) "sync" may cause life-cycle shortening.
           user   Allow an ordinary user to mount the filesystem.  The name of the
                  mounting user is written to mtab so  that  he  can  unmount  the
                  filesystem  again.   This  option  implies  the  options noexec,
                  nosuid, and nodev (unless overridden by subsequent  options,  as
                  in the option line user,exec,dev,suid).
           nouser Forbid  an  ordinary (i.e., non-root) user to mount the filesys-
                  tem.  This is the default.
           users  Allow every user to mount  and  unmount  the  filesystem.   This
                  option  implies  the  options  noexec, nosuid, and nodev (unless
                  overridden  by  subsequent  options,  as  in  the  option   line


           The  following options apply only to certain filesystems.  We sort them
           by filesystem. They all follow the -o flag.
           What options are supported depends a bit on the running  kernel.   More
           info  may  be  found  in  the  kernel  source  subdirectory  Documenta-

    Mount options for adfs

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

    Mount options for affs

           uid=value and gid=value
                  Set the owner and group of the root of the filesystem  (default:
                  uid=gid=0,  but  with option uid or gid without specified value,
                  the uid and gid of the current process are taken).
           setuid=value and setgid=value
                  Set the owner and group of all files.
                  Print an informational message for each successful mount.
                  Prefix used before volume name, when following a link.
                  Prefix  (of  length at most 30) used before '/' when following a
                  symbolic link.
                  (Default: 2.) Number of  unused  blocks  at  the  start  of  the
                  Give explicitly the location of the root block.
                  Give blocksize. Allowed values are 512, 1024, 2048, 4096.
                  These  options are accepted but ignored.  (However, quota utili-
                  ties may react to such strings in /etc/fstab.)

    Mount options for cifs

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

    Mount options for coherent


    Mount options for debugfs

           The debugfs filesystem is a pseudo filesystem, traditionally mounted on
           /sys/kernel/debug.  There are no mount options.

    Mount options for devpts

           The devpts filesystem is a pseudo filesystem, traditionally mounted  on
           /dev/pts.   In  order  to  acquire  a  pseudo terminal, a process opens
           /dev/ptmx; the number of the pseudo terminal is then made available  to
           the   process  and  the  pseudo  terminal  slave  can  be  accessed  as
           uid=value and gid=value
                  This sets the owner or the group of newly created  PTYs  to  the
                  specified values. When nothing is specified, they will be set to
                  the UID and GID of the creating process.  For example, if  there
                  is  a  tty group with GID 5, then gid=5 will cause newly created
                  PTYs to belong to the tty group.
                  This option is mainly used to support containers  in  the  linux
                  kernel. It is implemented in linux kernel versions starting with
                  2.6.29.  Further, this  mount  option  is  valid  only  if  CON-
                  FIG_DEVPTS_MULTIPLE_INSTANCES  is enabled in the kernel configu-
                  To use this option effectively, /dev/ptmx  must  be  a  symbolic
                  link  to  pts/ptmx.  See Documentation/filesystems/devpts.txt in
                  the linux kernel source tree for details.
                  Set the mode for the new ptmx device node in the devpts filesys-
                  With  the  support  for multiple instances of devpts (see newin-
                  stance option above), each instance has a private ptmx  node  in
                  the root of the devpts filesystem (typically /dev/pts/ptmx).
                  For compatibility with older versions of the kernel, the default
                  mode of the new ptmx node is 0000.  ptmxmode=value  specifies  a
                  more  useful  mode  for  the ptmx node and is highly recommended
                  when the newinstance option is specified.
                  This option is only implemented in linux kernel versions  start-
                  ing  with  2.6.29.  Further  this  option  is valid only if CON-
                  FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel  configu-

    Mount options for ext

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

    Mount options for ext2

           The 'ext2' filesystem is the standard Linux  filesystem.   Since  Linux
           2.5.46,  for  most  mount  options  the  default  is  determined by the
           filesystem superblock. Set them with tune2fs(8).
                  Support POSIX Access Control Lists (or not).
                  Set the behaviour  for  the  statfs  system  call.  The  minixdf
                  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
           debug  Print debugging info upon each (re)mount.
                  Define  the  behaviour  when  an  error is encountered.  (Either
                  ignore errors and just mark the filesystem  erroneous  and  con-
                  tinue,  or  remount  the filesystem read-only, or panic and halt
                  the system.)  The default is set in the  filesystem  superblock,
                  and can be changed using tune2fs(8).
           grpid|bsdgroups and nogrpid|sysvgroups
                  These  options  define  what group id a newly created file gets.
                  When grpid is set, it takes the group id  of  the  directory  in
                  which  it is created; otherwise (the default) it takes the fsgid
                  of the current process, unless the directory has the setgid  bit
                  set,  in  which case it takes the gid from the parent directory,
                  and also gets the setgid bit set if it is a directory itself.
                  These options are accepted but ignored.
           nobh   Do not attach buffer_heads to file pagecache. (Since 2.5.49.)
                  Disables 32-bit UIDs and GIDs.   This  is  for  interoperability
                  with older kernels which only store and expect 16-bit values.
           oldalloc or orlov
                  Use  old  allocator  or Orlov allocator for new inodes. Orlov is
           resgid=n and resuid=n
                  The ext2 filesystem reserves a certain percentage of the  avail-
                  able space (by default 5%, see mke2fs(8) and tune2fs(8)).  These
                  options determine who can use the  reserved  blocks.   (Roughly:
                  whoever  has  the  specified  uid,  or  belongs to the specified
           sb=n   Instead of block 1, use block n as  superblock.  This  could  be
                  useful  when  the filesystem has been damaged.  (Earlier, copies
                  of the superblock would be made every 8192 blocks: in  block  1,
                  8193,  16385,  ...  (and  one  got  thousands of copies on a big
                  filesystem).  Since  version  1.08,  mke2fs  has  a  -s  (sparse
                  superblock)  option  to reduce the number of backup superblocks,
                  and since version 1.15 this is the default. Note that  this  may
                  mean  that ext2 filesystems created by a recent mke2fs cannot be
                  mounted r/w under Linux 2.0.*.)  The block number here  uses  1k
                  units.  Thus,  if  you  want  to  use  logical  block 32768 on a
                  filesystem with 4k blocks, use "sb=131072".
                  Support "user." extended attributes (or not).
                  the ext3 filesystem's journal file;   ext3  will  create  a  new
                  journal,  overwriting  the  old contents of the file whose inode
                  number is inum.
                  When the external  journal  device's  major/minor  numbers  have
                  changed,  this option allows the user to specify the new journal
                  location.  The journal device  is  identified  through  its  new
                  major/minor numbers encoded in devnum.
                  Don't load the journal on mounting.  Note that if the filesystem
                  was not unmounted cleanly, skipping the journal replay will lead
                  to  the  filesystem  containing inconsistencies that can lead to
                  any number of problems.
                  Specifies the journalling  mode  for  file  data.   Metadata  is
                  always  journaled.   To use modes other than ordered on the root
                  filesystem, pass the mode to the kernel as boot parameter,  e.g.
                         All  data  is  committed  into the journal prior to being
                         written into the main filesystem.
                         This is the default mode.  All data  is  forced  directly
                         out  to  the main file system prior to its metadata being
                         committed to the journal.
                         Data ordering is not preserved - data may be written into
                         the main filesystem after its metadata has been committed
                         to the journal.  This is  rumoured  to  be  the  highest-
                         throughput  option.   It  guarantees  internal filesystem
                         integrity, however it can allow old  data  to  appear  in
                         files after a crash and journal recovery.
           barrier=0 / barrier=1
                  This  enables/disables  barriers.   barrier=0  disables it, bar-
                  rier=1 enables it.  Write barriers enforce proper on-disk order-
                  ing  of  journal commits, making volatile disk write caches safe
                  to use,  at  some  performance  penalty.   The  ext3  filesystem
                  enables  write  barriers by default.  Be sure to enable barriers
                  unless your disks are battery-backed one way or another.  Other-
                  wise you risk filesystem corruption in case of power failure.
                  Sync  all  data  and  metadata  every nrsec seconds. The default
                  value is 5 seconds. Zero means default.
           grpquota,  usrquota  and  [no]bh are backwardly compatible with ext3 or
                  Enable checksumming of  the  journal  transactions.   This  will
                  allow  the recovery code in e2fsck and the kernel to detect cor-
                  ruption in the kernel.  It is a compatible change  and  will  be
                  ignored by older kernels.
                  Commit block can be written to disk without waiting for descrip-
                  tor blocks. If enabled older kernels cannot  mount  the  device.
                  This will enable
                  Update the ext4 filesystem's journal to the current format.
           barrier=0 / barrier=1 / barrier / nobarrier
                  This enables/disables the use of write barriers in the jbd code.
                  barrier=0 disables, barrier=1 enables.  This also requires an IO
                  stack  which can support barriers, and if jbd gets an error on a
                  barrier write, it will disable again with a warning.  Write bar-
                  riers enforce proper on-disk ordering of journal commits, making
                  volatile disk write caches safe  to  use,  at  some  performance
                  penalty.   If  your  disks  are  battery-backed  in  one  way or
                  another, disabling barriers may safely improve performance.  The
                  mount  options  "barrier"  and  "nobarrier"  can also be used to
                  enable or disable barriers,  for  consistency  with  other  ext4
                  mount options.
                  The ext4 filesystem enables write barriers by default.
                  This tuning parameter controls the maximum number of inode table
                  blocks that ext4's inode table readahead algorithm will pre-read
                  into  the  buffer  cache.   The  value must be a power of 2. The
                  default value is 32 blocks.
                  Number of filesystem blocks that mballoc will  try  to  use  for
                  allocation  size  and alignment. For RAID5/6 systems this should
                  be the number of data disks *  RAID  chunk  size  in  filesystem
                  Deferring block allocation until write-out time.
                  Disable  delayed  allocation. Blocks are allocation when data is
                  copied from user to page cache.
                  mization can be turned off entirely by setting max_batch_time to
                  This  parameter  sets the commit time (as described above) to be
                  at least  min_batch_time.  It  defaults  to  zero  microseconds.
                  Increasing  this  parameter may improve the throughput of multi-
                  threaded, synchronous workloads on very fast disks, at the  cost
                  of increasing latency.
                  The  I/O  priority (from 0 to 7, where 0 is the highest priorty)
                  which should be used for I/O operations submitted by  kjournald2
                  during  a  commit  operation.   This  defaults  to 3, which is a
                  slightly higher priority than the default I/O priority.
           abort  Simulate the effects of calling ext4_abort() for debugging  pur-
                  poses.   This  is  normally  used  while remounting a filesystem
                  which is already mounted.
                  Many broken applications don't use fsync() when  noauto_da_alloc
                  replacing existing files via patterns such as
                  fd  =  open("")/write(fd,..)/close(fd)/ rename("",
                  or worse yet
                  fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
                  If auto_da_alloc is enabled, ext4 will detect  the  replace-via-
                  rename  and  replace-via-truncate  patterns  and  force that any
                  delayed allocation blocks are allocated such that  at  the  next
                  journal  commit,  in  the  default  data=ordered  mode, the data
                  blocks of the new file are forced to disk  before  the  rename()
                  operation  is commited.  This provides roughly the same level of
                  guarantees as ext3, and avoids the  "zero-length"  problem  that
                  can  happen  when a system crashes before the delayed allocation
                  blocks are forced to disk.
                  Controls whether ext4 should issue discard/TRIM commands to  the
                  underlying  block  device when blocks are freed.  This is useful
                  for SSD devices and sparse/thinly-provisioned LUNs,  but  it  is
                  off by default until sufficient testing has been done.
                  Disables  32-bit  UIDs  and  GIDs.  This is for interoperability
                  with  older kernels which only store and expect 16-bit values.
           resize Allows to resize filesystem to the  end  of  the  last  existing
                  Controls whether or not ext4 should use the DIO read locking. If
                  the dioread_nolock option is specified ext4 will allocate unini-
                  tialized  extent  before  buffer write and convert the extent to
                  initialized after IO completes.  This approach allows ext4  code
                  to  avoid  using inode mutex, which improves scalability on high
                  speed storages. However this does not work with nobh option  and
                  the  mount  will fail. Nor does it work with data journaling and
                  dioread_nolock option will be ignored with kernel warning.  Note
                  that  dioread_nolock  code  path  is  only used for extent-based
                  files.  Because of the restrictions this options comprises it is
                  off by default (e.g. dioread_lock).
                  Enable  64-bit  inode  version  support.  This  option is off by

    Mount options for fat

           (Note: fat is not a separate filesystem,  but  a  common  part  of  the
           msdos, umsdos and vfat filesystems.)
                  Set blocksize (default 512). This option is obsolete.
           uid=value and gid=value
                  Set the owner and group of all files.  (Default: the uid and gid
                  of the current process.)
                  Set the umask (the bitmask  of  the  permissions  that  are  not
                  present).  The default is the umask of the current process.  The
                  value is given in octal.
                  Set the umask applied to directories only.  The default  is  the
                  umask of the current process.  The value is given in octal.
                  Set the umask applied to regular files only.  The default is the
                  umask of the current process.  The value is given in octal.
                  This option controls the permission check of mtime/atime.
                  20     If current process is in group of file's  group  ID,  you
                         can change timestamp.
                  2      Other users can change timestamp.
                  The  default  is  set  from 'dmask' option. (If the directory is
                  writable, utime(2) is also allowed. I.e. ~dmask & 022)
                         Like "relaxed", but many special  characters  (*,  ?,  <,
                         spaces, etc.) are rejected.  This is the default.
                         Like  "normal",  but names may not contain long parts and
                         special characters that are sometimes used on Linux,  but
                         are  not  accepted by MS-DOS are rejected. (+, =, spaces,
                  Sets the codepage for converting to shortname characters on  FAT
                  and VFAT filesystems. By default, codepage 437 is used.
                  The fat filesystem can perform CRLF<-->NL (MS-DOS text format to
                  UNIX text format) conversion in the kernel. The  following  con-
                  version modes are available:
                  binary no translation is performed.  This is the default.
                  text   CRLF<-->NL translation is performed on all files.
                  auto   CRLF<-->NL  translation  is  performed  on all files that
                         don't have a "well-known binary" extension. The  list  of
                         known  extensions  can  be  found  at  the  beginning  of
                         fs/fat/misc.c (as of 2.0, the list  is:  exe,  com,  bin,
                         app,  sys,  drv,  ovl, ovr, obj, lib, dll, pif, arc, zip,
                         lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz,  gz,  tgz,
                         deb,  gif,  bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl,
                  Programs that do computed lseeks won't like in-kernel text  con-
                  version.   Several  people  have  had  their data ruined by this
                  translation. Beware!
                  For filesystems mounted in binary mode, a conversion tool (from-
                  dos/todos) is available. This option is obsolete.
                  Forces the driver to use the CVF (Compressed Volume File) module
                  cvf_module instead of auto-detection.  If  the  kernel  supports
                  kmod, the cvf_format=xxx option also controls on-demand CVF mod-
                  ule loading.  This option is obsolete.
                  Option passed to the CVF module. This option is obsolete.
           debug  Turn on the debug flag.  A version string and a list of filesys-
                  tem  parameters  will be printed (these data are also printed if
                  the parameters appear to be inconsistent).
           quiet  Turn on the quiet flag.  Attempts to chown or chmod files do not
                  return errors, although they fail. Use with caution!
                  If set, the execute permission bits of the file will be  allowed
                  only  if  the extension part of the name is .EXE, .COM, or .BAT.
                  Not set by default.
                  If set, ATTR_SYS attribute on FAT is handled as  IMMUTABLE  flag
                  on Linux.  Not set by default.
           flush  If set, the filesystem will try to flush to disk more early than
                  normal.  Not set by default.
                  Use the "free clusters" value stored on FSINFO. It'll be used to
                  determine  number  of  free  clusters without scanning disk. But
                  it's not used by default, because recent Windows don't update it
                  correctly  in  some case. If you are sure the "free clusters" on
                  FSINFO is correct, by this option you can avoid scanning disk.
           dots, nodots, dotsOK=[yes|no]
                  Various misguided attempts to force Unix or DOS conventions onto
                  a FAT filesystem.

    Mount options for hfs

           creator=cccc, type=cccc
                  Set  the  creator/type  values as shown by the MacOS finder used
                  for creating new files.  Default values: '????'.
           uid=n, gid=n
                  Set the owner and group of all files.  (Default: the uid and gid
                  of the current process.)
           dir_umask=n, file_umask=n, umask=n
                  Set  the  umask  used for all directories, all regular files, or
                  all files and directories.  Defaults to the umask of the current
                  Select  the  CDROM  session  to mount.  Defaults to leaving that
                  decision to the CDROM driver.  This option will fail  with  any-
                  thing but a CDROM as underlying device.
           part=n Select partition number n from the device.  Only makes sense for
                  CDROMS.  Defaults to not parsing the partition table at all.
           quiet  Don't complain about invalid mount options.
                  For conv=text, delete some random CRs (in particular,  all  fol-
                  lowed by NL) when reading a file.  For conv=auto, choose more or
                  less  at  random  between  conv=binary   and   conv=text.    For
                  conv=binary, just read what is in the file. This is the default.
                  Do not abort mounting when certain consistency checks fail.

    Mount options for iso9660

           ISO 9660 is a standard describing a filesystem structure to be used  on
           CD-ROMs.  (This filesystem type is also seen on some DVDs. See also the
           udf filesystem.)
           Normal iso9660  filenames  appear  in  a  8.3  format  (i.e.,  DOS-like
           restrictions on filename length), and in addition all characters are in
           upper case.  Also there is no field  for  file  ownership,  protection,
           number of links, provision for block/character devices, etc.
           Rock  Ridge  is an extension to iso9660 that provides all of these unix
           like features.  Basically there are extensions to each directory record
           that  supply  all of the additional information, and when Rock Ridge is
           in  use,  the  filesystem  is  indistinguishable  from  a  normal  UNIX
           filesystem (except that it is read-only, of course).
           norock Disable the use of Rock Ridge extensions, even if available. Cf.
                  Disable the use of Microsoft Joliet extensions, even  if  avail-
                  able. Cf. map.
                  With  check=relaxed, a filename is first converted to lower case
                  before doing the  lookup.   This  is  probably  only  meaningful
                  together with norock and map=normal.  (Default: check=strict.)
           uid=value and gid=value
                  Give all files in the filesystem the indicated user or group id,
                  possibly overriding the information  found  in  the  Rock  Ridge
                  extensions.  (Default: uid=0,gid=0.)
                  For  non-Rock  Ridge volumes, normal name translation maps upper
                  to lower case ASCII, drops a trailing ';1', and converts ';'  to
                  '.'.   With  map=off  no  name  translation is done. See norock.
                  (Default: map=normal.)  map=acorn is like  map=normal  but  also
                  apply Acorn extensions if present.
                  (Default:  conv=binary.)   Since Linux 1.3.54 this option has no
                  effect anymore.  (And non-binary settings used to be  very  dan-
                  gerous, possibly leading to silent data corruption.)
           cruft  If  the high byte of the file length contains other garbage, set
                  this mount option to ignore the high  order  bits  of  the  file
                  length.  This implies that a file cannot be larger than 16MB.
                  Select number of session on multisession CD. (Since 2.3.4.)
                  Session begins from sector xxx. (Since 2.3.4.)
           The following options are the same as for vfat and specifying them only
           makes sense when using discs encoded using  Microsoft's  Joliet  exten-
                  Character set to use for converting 16 bit Unicode characters on
                  CD to 8 bit characters. The default is iso8859-1.
           utf8   Convert 16 bit Unicode characters on CD to UTF-8.

    Mount options for jfs

                  Character set to use for converting from Unicode to ASCII.   The
                  default  is  to  do  no conversion.  Use iocharset=utf8 for UTF8
                  translations.  This requires CONFIG_NLS_UTF8 to be  set  in  the
                  kernel .config file.
                  Resize  the  volume to value blocks. JFS only supports growing a
                  volume, not shrinking it. This option is  only  valid  during  a
                  remount,  when the volume is mounted read-write. The resize key-
                  word with no value will grow the volume to the full size of  the
                  Do  not write to the journal.  The primary use of this option is
                  to allow for higher performance when  restoring  a  volume  from
                  backup  media.  The integrity of the volume is not guaranteed if
                  the system abnormally abends.
                  Default.  Commit metadata changes  to  the  journal.   Use  this
                  option to remount a volume where the nointegrity option was pre-
                  viously specified in order to restore normal behavior.
                  Define the behaviour when  an  error  is  encountered.   (Either
           sistency, it reports an error and sets the file system  read-only.  The
           filesystem can be made writeable again by remounting it.

    Mount options for ncpfs

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

    Mount options for nfs and nfs4

           See the options section of the nfs(5) man page (nfs-utils package  must
           be installed).
           The  nfs  and  nfs4  implementation expects a binary argument (a struct
           nfs_mount_data) to the mount system call. This argument is  constructed
           by  mount.nfs(8)  and the current version of mount (2.13) does not know
           anything about nfs and nfs4.

    Mount options for ntfs

                  Character set to use when returning file  names.   Unlike  VFAT,
                  NTFS  suppresses  names  that  contain unconvertible characters.
                  New name for the option earlier called iocharset.
           utf8   Use UTF-8 for converting file names.
                  For 0 (or 'no' or 'false'), do  not  use  escape  sequences  for
                  unknown  Unicode  characters.   For 1 (or 'yes' or 'true') or 2,
                  use vfat-style 4-byte escape sequences starting with ":". Here 2
                  give  a  little-endian  encoding  and  1 a byteswapped bigendian
                  If enabled (posix=1), the filesystem distinguishes between upper
                  and  lower case. The 8.3 alias names are presented as hard links
                  instead of being suppressed. This option is obsolete.
           uid=value, gid=value and umask=value
                  Set the file permission on the filesystem.  The umask  value  is
                  given in octal.  By default, the files are owned by root and not
                  readable by somebody else.

    Mount options for proc

           uid=value and gid=value
                  filesystem, using the 3.6 format for newly created objects. This
                  filesystem will no longer be compatible with reiserfs 3.5 tools.
                  Choose which hash function  reiserfs  will  use  to  find  files
                  within directories.
                         A hash invented by Yury Yu. Rupasov.  It is fast and pre-
                         serves locality,  mapping  lexicographically  close  file
                         names  to  close  hash values.  This option should not be
                         used, as it causes a high probability of hash collisions.
                  tea    A    Davis-Meyer    function    implemented   by   Jeremy
                         Fitzhardinge.  It uses hash permuting bits in  the  name.
                         It  gets  high randomness and, therefore, low probability
                         of hash collisions at some CPU cost.  This may be used if
                         EHASHCOLLISION errors are experienced with the r5 hash.
                  r5     A  modified  version  of  the rupasov hash. It is used by
                         default and is the best choice unless the filesystem  has
                         huge directories and unusual file-name patterns.
                  detect Instructs  mount  to detect which hash function is in use
                         by examining the filesystem being mounted,  and to  write
                         this  information  into  the reiserfs superblock. This is
                         only useful on the first mount of an old format  filesys-
                  Tunes the block allocator. This may provide performance improve-
                  ments in some situations.
                  Tunes the block allocator. This may provide performance improve-
                  ments in some situations.
                  Disable  the  border  allocator  algorithm  invented by Yury Yu.
                  Rupasov.  This may provide performance improvements in some sit-
           nolog  Disable   journalling.  This  will  provide  slight  performance
                  improvements in some situations at the cost of losing reiserfs's
                  fast  recovery  from  crashes.  Even with this option turned on,
                  reiserfs still performs all  journalling  operations,  save  for
                  actual  writes  into  its  journalling  area.  Implementation of
                  nolog is a work in progress.
           notail By  default,  reiserfs  stores  small  files  and  'file  tails'
                  directly  into  its  tree.  This confuses some utilities such as
                  LILO(8).  This option is used to disable packing of  files  into
                  Enable Extended User Attributes. See the attr(5) manual page.
           acl    Enable POSIX Access Control Lists. See the acl(5) manual page.
           barrier=none / barrier=flush
                  This  enables/disables the use of write barriers in the journal-
                  ing code.  barrier=none disables it, barrier=flush  enables  it.
                  Write  barriers  enforce proper on-disk ordering of journal com-
                  mits, making volatile disk write caches safe  to  use,  at  some
                  performance  penalty.  The  reiserfs  filesystem does not enable
                  write barriers by default. Be sure  to  enable  barriers  unless
                  your  disks are battery-backed one way or another. Otherwise you
                  risk filesystem corruption in case of power failure.

    Mount options for romfs


    Mount options for squashfs


    Mount options for smbfs

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

    Mount options for sysv


    Mount options for tmpfs

                  Override  default  maximum  size of the filesystem.  The size is
                  given in bytes, and rounded up to entire pages.  The default  is
                  half  of  the memory. The size parameter also accepts a suffix %
                  to limit this tmpfs instance to that percentage of your physical
                  RAM:  the default, when neither size nor nr_blocks is specified,
                  is size=50%
                  The same as size, but in blocks of PAGE_CACHE_SIZE
                  The maximum number of inodes for this instance. The  default  is
                  half  of the number of your physical RAM pages, or (on a machine
                  with highmem) the number of lowmem RAM pages, whichever  is  the
                  instance (if the kernel CONFIG_NUMA is enabled) - which  can  be
                  adjusted on the fly via 'mount -o remount ...'
                         prefers to allocate memory from the local node
                         prefers to allocate memory from the given Node
                         allocates memory only from nodes in NodeList
                         prefers to allocate from each node in turn
                         allocates from each node of NodeList in turn.
                  The NodeList format is a comma-separated list of decimal numbers
                  and ranges, a range being two hyphen-separated decimal  numbers,
                  the  smallest  and largest node numbers in the range.  For exam-
                  ple, mpol=bind:0-3,5,7,9-15
                  Note that trying to mount a tmpfs with an mpol option will  fail
                  if  the  running  kernel does not support NUMA; and will fail if
                  its nodelist specifies a node which is not online.  If your sys-
                  tem  relies  on  that tmpfs being mounted, but from time to time
                  runs a kernel built without  NUMA  capability  (perhaps  a  safe
                  recovery  kernel), or with fewer nodes online, then it is advis-
                  able to omit the mpol option from automatic mount  options.   It
                  can  be added later, when the tmpfs is already mounted on Mount-
                  Point, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.

    Mount options for ubifs

           UBIFS is a flash file system which works on top of  UBI  volumes.  Note
           that atime is not supported and is always turned off.
           The device name may be specified as
                  ubiX_Y UBI device number X, volume number Y
                  ubiY   UBI device number 0, volume number Y
                         UBI device number X, volume with name NAME
                         UBI device number 0, volume with name NAME
           Alternative !  separator may be used instead of :.
           The following mount options are available:
                  Do  not  check  data  CRC-32  checksums.  With  this option, the
                  filesystem does not check CRC-32 checksum for data, but it  does
                  check it for the internal indexing information. This option only
                  affects reading, not writing. CRC-32 is always  calculated  when
                  writing the data.
                  Select  the  default compressor which is used when new files are
                  written. It is  still  possible  to  read  compressed  files  if
                  mounted with the none option.

    Mount options for udf

           udf  is  the  "Universal Disk Format" filesystem defined by the Optical
           Storage Technology Association, and is often  used  for  DVD-ROM.   See
           also iso9660.
           gid=   Set the default group.
           umask= Set the default umask.  The value is given in octal.
           uid=   Set the default user.
           unhide Show otherwise hidden files.
                  Show deleted files in lists.
                  Unset strict conformance.
                  Set the NLS character set.
           bs=    Set the block size. (May not work unless 2048.)
           novrs  Skip volume sequence recognition.
                  Set the CDROM session counting from 0. Default: last session.
                  Override standard anchor location. Default: 256.
                  Override the VolumeDesc location. (unused)
                  Override the PartitionDesc location. (unused)
                  Set the last block of the filesystem.
                  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
                  sun    For filesystems created by SunOS or Solaris on Sparc.
                  sunx86 For filesystems created by Solaris on x86.
                  hp     For filesystems created by HP-UX, read-only.
                         For  filesystems  created  by  NeXTStep (on NeXT station)
                         (currently read only).
                         For NextStep CDROMs (block_size == 2048), read-only.
                         For  filesystems  created  by  OpenStep  (currently  read
                         only).   The  same filesystem type is also used by Mac OS
                  Set behaviour on error:
                  panic  If an error is encountered, cause a kernel panic.
                         These mount options don't do anything at present; when an
                         error is encountered only a console message is printed.

    Mount options for umsdos

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

    Mount options for vfat

           First of all, the mount options for fat  are  recognized.   The  dotsOK
           option is explicitly killed by vfat.  Furthermore, there are
                  Translate   unhandled  Unicode  characters  to  special  escaped
                  sequences.  This lets you backup and restore filenames that  are
                  created  with any Unicode characters. Without this option, a '?'
                  is used when no translation is possible. The escape character is
                  ':'  because it is otherwise illegal on the vfat filesystem. The
                  Defines the behaviour for  creation  and  display  of  filenames
                  which fit into 8.3 characters. If a long name for a file exists,
                  it will always be preferred display. There are four modes: :
                  lower  Force the short name to lower case upon display; store  a
                         long name when the short name is not all upper case. This
                         mode is the default.
                  win95  Force the short name to upper case upon display; store  a
                         long name when the short name is not all upper case.
                  winnt  Display  the  shortname as is; store a long name when the
                         short name is not all lower case or all upper case.
                  mixed  Display the short name as is; store a long name when  the
                         short name is not all upper case.

    Mount options for usbfs

           devuid=uid and devgid=gid and devmode=mode
                  Set  the  owner  and  group  and mode of the device files in the
                  usbfs filesystem (default: uid=gid=0, mode=0644).  The  mode  is
                  given in octal.
           busuid=uid and busgid=gid and busmode=mode
                  Set  the  owner and group and mode of the bus directories in the
                  usbfs filesystem (default: uid=gid=0, mode=0555).  The  mode  is
                  given in octal.
           listuid=uid and listgid=gid and listmode=mode
                  Set  the  owner and group and mode of the file devices (default:
                  uid=gid=0, mode=0444). The mode is given in octal.

    Mount options for xenix


    Mount options for xfs

                  Sets the buffered I/O end-of-file preallocation size when  doing
                  delayed allocation writeout (default size is 64KiB).  Valid val-
                  ues for this option are page size (typically  4KiB)  through  to
                  1GiB, inclusive, in power-of-2 increments.
                  The  options enable/disable (default is enabled) an "opportunis-
                  tic"  improvement  to  be  made  in  the  way  inline   extended
           grpid|bsdgroups and nogrpid|sysvgroups
                  These options define what group ID a newly  created  file  gets.
                  When  grpid  is  set,  it takes the group ID of the directory in
                  which it is created; otherwise (the default) it takes the  fsgid
                  of  the current process, unless the directory has the setgid bit
                  set, in which case it takes the gid from the  parent  directory,
                  and also gets the setgid bit set if it is a directory itself.
                  Sets  the  number  of hash buckets available for hashing the in-
                  memory inodes of the specified mount point.  If a value of  zero
                  is  used,  the  value  selected by the default algorithm will be
                  displayed in /proc/mounts.
                  When inode clusters are emptied of inodes, keep them  around  on
                  the  disk (ikeep) - this is the traditional XFS behaviour and is
                  still the default for now.   Using  the  noikeep  option,  inode
                  clusters are returned to the free space pool.
                  Indicates  that  XFS is allowed to create inodes at any location
                  in the filesystem, including those which will  result  in  inode
                  numbers  occupying  more  than 32 bits of significance.  This is
                  provided for backwards compatibility, but  causes  problems  for
                  backup applications that cannot handle large inode numbers.
                  If  nolargeio  is specified, the optimal I/O reported in st_blk-
                  size by stat(2) will be as  small  as  possible  to  allow  user
                  applications  to  avoid  inefficient  read/modify/write I/O.  If
                  largeio is specified, a filesystem that has a  swidth  specified
                  will  return  the  swidth value (in bytes) in st_blksize. If the
                  filesystem does not have a swidth specified but does specify  an
                  allocsize  then  allocsize  (in bytes) will be returned instead.
                  If neither of these two options are specified,  then  filesystem
                  will behave as if nolargeio was specified.
                  Set  the  number  of in-memory log buffers.  Valid numbers range
                  from 2-8 inclusive.  The default value is 8 buffers for filesys-
                  tems with a blocksize of 64KiB, 4 buffers for filesystems with a
                  blocksize of 32KiB, 3 buffers for filesystems with  a  blocksize
                  of 16KiB and 2 buffers for all other configurations.  Increasing
                  the number of buffers may increase performance on some workloads
                  at  the  cost  of the memory used for the additional log buffers
                  and their associated control structures.
                  Set the size of each in-memory log buffer.  Size may  be  speci-
                  fied  in  bytes, or in kilobytes with a "k" suffix.  Valid sizes
                  for version 1 and version 2  logs  are  16384  (16k)  and  32768
                  included in the DMAPI mount event, and should be the path of the
                  actual mountpoint that is used.
                  Data allocations will not be aligned at stripe unit  boundaries.
                  Access timestamps are not updated when a file is read.
                  The filesystem will be mounted without running log recovery.  If
                  the filesystem was not cleanly unmounted, it  is  likely  to  be
                  inconsistent  when  mounted  in  norecovery mode.  Some files or
                  directories may not be accessible because of this.   Filesystems
                  mounted  norecovery  must be mounted read-only or the mount will
           nouuid Don't check for double mounted filesystems using the  filesystem
                  uuid.  This is useful to mount LVM snapshot volumes.
                  Make  O_SYNC writes implement true O_SYNC.  WITHOUT this option,
                  Linux XFS behaves as if an osyncisdsync option  is  used,  which
                  will make writes to files opened with the O_SYNC flag set behave
                  as if the O_DSYNC flag had been used instead.  This  can  result
                  in better performance without compromising data safety.  However
                  if this option is not in effect, timestamp updates  from  O_SYNC
                  writes  can be lost if the system crashes.  If timestamp updates
                  are critical, use the osyncisosync option.
                  User disk quota  accounting  enabled,  and  limits  (optionally)
                  enforced.  Refer to xfs_quota(8) for further details.
                  Group  disk  quota  accounting  enabled  and limits (optionally)
                  enforced. Refer to xfs_quota(8) for further details.
                  Project disk quota accounting enabled  and  limits  (optionally)
                  enforced. Refer to xfs_quota(8) for further details.
           sunit=value and swidth=value
                  Used to specify the stripe unit and width for a RAID device or a
                  stripe volume.  value must be specified in 512-byte block units.
                  If this option is not specified and the filesystem was made on a
                  stripe volume or the stripe width or unit were specified for the
                  RAID  device  at  mkfs  time,  then  the  mount system call will
                  restore the value from the superblock.  For filesystems that are
                  made  directly  on  RAID  devices,  these options can be used to
                  override the information in the  superblock  if  the  underlying
                  disk  layout changes after the filesystem has been created.  The


           One  further possible type is a mount via the loop device. For example,
           the command
             mount /tmp/fdimage /mnt -t vfat -o loop=/dev/loop3
           will set up the loop  device  /dev/loop3  to  correspond  to  the  file
           /tmp/fdimage, and then mount this device on /mnt.
           This type of mount knows about four options, namely loop, offset, size-
           limit and encryption, that are really options  to  losetup(8).   (These
           options  can  be  used  in addition to those specific to the filesystem
           If no explicit loop device is mentioned (but just an option  '-o  loop'
           is  given), then mount will try to find some unused loop device and use
           Since Linux 2.6.25 is supported auto-destruction of  loop  devices  and
           then  any  loop device allocated by mount will be freed by umount inde-
           pendently on /etc/mtab.
           You can also free a loop device by hand, using 'losetup -d' or  'umount


           mount has the following return codes (the bits can be ORed):
           0      success
           1      incorrect invocation or permissions
           2      system error (out of memory, cannot fork, no more loop devices)
           4      internal mount bug
           8      user interrupt
           16     problems writing or locking /etc/mtab
           32     mount failure
           64     some mount succeeded


           The syntax of external mount helpers is:
                  /sbin/mount.<suffix> spec dir [-sfnv] [-o options] [-t type.sub-
           /etc/filesystems  a list of filesystem types to try


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


           It is possible for a corrupted filesystem to cause a crash.
           Some Linux filesystems don't support -o sync and -o dirsync (the  ext2,
           ext3,  fat  and  vfat  filesystems do support synchronous updates (a la
           BSD) when mounted with the sync option).
           The -o remount may not be able to change mount parameters (all  ext2fs-
           specific  parameters,  except  sb,  are  changeable with a remount, for
           example, but you can't change gid or umask for the fatfs).
           Mount by label or uuid will work only if your devices  have  the  names
           listed  in  /proc/partitions.   In  particular, it may well fail if the
           kernel was compiled with devfs but devfs is not mounted.
           It is possible that files /etc/mtab and /proc/mounts don't  match.  The
           first  file is based only on the mount command options, but the content
           of the second file also depends on the kernel and others settings (e.g.
           remote  NFS  server.  In  particular case the mount command may reports
           unreliable information about a NFS mount  point  and  the  /proc/mounts
           file usually contains more reliable information.)
           Checking  files  on NFS filesystem referenced by file descriptors (i.e.
           the fcntl and ioctl families of functions)  may  lead  to  inconsistent
           result  due  to the lack of consistency check in kernel even if noac is


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


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

    Linux 2.6 2004-12-16 MOUNT(8)


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