MOUNT(8)                     System Administration                    MOUNT(8)
NAME
       mount - mount a filesystem

SYNOPSIS
       mount [-l|-h|-V]

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

       mount [-fnrsvw] [-o options] device|dir

       mount [-fnrsvw] [-t fstype] [-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 filesystem found
       on some device to the big file tree.  Conversely, the umount(8) command
       will detach it again.

       The standard form of the mount command is:

              mount -t type device dir

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

       If only the directory or the device is given, for example:

              mount /dir

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

              mount --target /mountpoint

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

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

              The following command lists all  mounted  filesystems  (of  type
              type):

                     mount [-l] [-t type]

              The option -l adds labels to this listing.  See below.

       The device indication.
              Most  devices  are  indicated  by a filename (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 also possible to indicate a block spe-
              cial  device  using its filesystem label or UUID (see the -L and
              -U options below), or its partition label or  UUID.   (Partition
              identifiers  are supported for example for GUID Partition Tables
              (GPT).)

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

              The  recommended  setup is to use tags (e.g. LABEL=label) rather
              than /dev/disk/by-{label,uuid,partuuid,partlabel} udev  symlinks
              in the /etc/fstab file.  Tags are more readable, robust and por-
              table.  The mount(8) command internally uses udev  symlinks,  so
              the  use  of  symlinks in /etc/fstab has no advantage over tags.
              For more details see libblkid(3).

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

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

       The /etc/fstab, /etc/mtab and /proc/mounts files.
              The file /etc/fstab (see fstab(5)), may contain lines describing
              what devices are usually mounted  where,  using  which  options.
              The default location of the fstab(5) file can be overridden with
              the  --fstab  path  command-line  option  (see  below  for  more
              details).

              The command

                     mount -a [-t type] [-O optlist]

              (usually given in a bootscript) causes all filesystems mentioned
              in fstab (of the proper type and/or having  or  not  having  the
              proper  options)  to  be  mounted as indicated, except for those
              whose line contains the noauto keyword.  Adding  the  -F  option
              will make mount fork, so that the filesystems are mounted simul-
              taneously.

              When mounting a filesystem mentioned in fstab or mtab,  it  suf-
              fices  to  specify  on the command line only the device, or only
              the mount point.

              The programs mount and umount traditionally maintained a list of
              currently  mounted filesystems in the file /etc/mtab.  This real
              mtab file is still supported, but on current Linux systems it is
              better  to  make it a symlink to /proc/mounts instead, because a
              regular mtab file maintained in userspace cannot  reliably  work
              with namespaces, containers and other advanced Linux features.

              If no arguments are given to mount, the list of mounted filesys-
              tems is printed.

              If you want to override mount options from /etc/fstab  you  have
              to use the -o option:

                     mount device|dir -o options

              and  then  the  mount  options  from  the  command  line will be
              appended to the list of  options  from  /etc/fstab.   The  usual
              behavior  is  that the last option wins if there are conflicting
              ones.

              The mount program does not read  the  /etc/fstab  file  if  both
              device (or LABEL, UUID, PARTUUID or PARTLABEL) and dir are spec-
              ified.  For example, to mount device foo at /dir:

                     mount /dev/foo /dir

       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 filesystem.

              Thus, given a line

                     /dev/cdrom  /cd  iso9660  ro,user,noauto,unhide

              any user can mount the iso9660 filesystem found on  an  inserted
              CDROM using the command

                     mount /dev/cdrom

              or

                     mount /cd

              For  more  details,  see fstab(5).  Only the user that mounted a
              filesystem can unmount it again.  If any user should be able  to
              unmount  it,  then  use users instead of user in the fstab line.
              The owner option  is  similar  to  the  user  option,  with  the
              restriction that the user must be the owner of the special file.
              This may be useful e.g. for /dev/fd if a login script makes  the
              console user owner of this device.  The group option is similar,
              with the restriction that the user must be member of  the  group
              of the special file.

       The bind mounts.
              Since  Linux  2.4.0  it  is possible to remount part of the file
              hierarchy somewhere else.  The call is:

                     mount --bind olddir newdir

              or by using this fstab entry:

                     /olddir /newdir none bind

              After this call the same contents are accessible in two  places.
              One  can  also  remount  a single file (on a single file).  It's
              also possible to use the bind mount to create a mountpoint  from
              a regular directory, for example:

                     mount --bind foo foo

              The bind mount call attaches only (part of) a single filesystem,
              not possible submounts.  The  entire  file  hierarchy  including
              submounts is attached a second place by using:

                     mount --rbind olddir newdir

              Note  that  the filesystem mount options will remain the same as
              those on the original mount point.

              mount(8) since v2.27 allow to change the options by passing  the
              -o option along with --bind for example:

                     mount --bind,ro foo foo

              This  feature  is not supported by Linux kernel and it is imple-
              mented in userspace by additional remount mount(2) syscall. This
              solution is not atomic.

              The  alternative  (classic) way to create a read-only bind mount
              is to use remount operation, for example:

                     mount --bind olddir newdir
                     mount -o remount,ro,bind olddir newdir

              Note that read-only bind will create a read-only mountpoint (VFS
              entry),  but  the  original  filesystem superblock will still be
              writable, meaning that the olddir  will  be  writable,  but  the
              newdir will be read-only.

              It's impossible to change mount options recursively (for example
              b  -o rbind,ro).

       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

              This  will  cause  the  contents which previously appeared under
              olddir to now be accessible under newdir.  The physical location
              of  the  files  is  not  changed.   Note that olddir has to be a
              mountpoint.

              Note also that moving a mount residing under a shared  mount  is
              invalid  and  unsupported.  Use findmnt -o TARGET,PROPAGATION to
              see the current propagation flags.

       The shared subtree 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 the ability to create mirrors of that mount  such  that
              mounts  and  unmounts within any of the mirrors propagate to the
              other mirror.  A slave mount receives propagation from its  mas-
              ter, but not vice versa.  A private mount carries no propagation
              abilities.  An unbindable mount is a private mount which  cannot
              be  cloned through a bind operation.  The detailed semantics are
              documented in  Documentation/filesystems/sharedsubtree.txt  file
              in the kernel source tree.

              Supported operations are:

                     mount --make-shared mountpoint
                     mount --make-slave mountpoint
                     mount --make-private mountpoint
                     mount --make-unbindable mountpoint

              The  following commands allow one to recursively change the type
              of all the mounts under a given mountpoint.

                     mount --make-rshared mountpoint
                     mount --make-rslave mountpoint
                     mount --make-rprivate mountpoint
                     mount --make-runbindable mountpoint

              mount(8) does not read fstab(5) when  a  --make-*  operation  is
              requested.  All necessary information has to be specified on the
              command line.

              Note that the Linux kernel does not  allow  to  change  multiple
              propagation  flags with a single mount(2) syscall, and the flags
              cannot be mixed with other mount options.

              Since util-linux 2.23 the mount command allows  to  use  several
              propagation  flags  together  and also together with other mount
              operations.  This  feature  is  EXPERIMENTAL.   The  propagation
              flags  are applied by additional mount(2) syscalls when the pre-
              ceding mount operations were successful.   Note  that  this  use
              case  is  not atomic.  It is possible to specify the propagation
              flags in fstab(5) as  mount  options  (private,  slave,  shared,
              unbindable, rprivate, rslave, rshared, runbindable).

              For example:

                     mount --make-private --make-unbindable /dev/sda1 /foo

              is the same as:

                     mount /dev/sda1 /foo
                     mount --make-private /foo
                     mount --make-unbindable /foo

COMMAND-LINE OPTIONS
       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.

       The command mount  does  not  pass  all  command-line  options  to  the
       /sbin/mount.suffix  mount helpers.  The interface between mount and the
       mount helpers is described below in the section EXTERNAL HELPERS.

       Command-line options available for the mount command are:

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

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

       -c, --no-canonicalize
              Don't  canonicalize  paths.  The mount command canonicalizes all
              paths (from command line or fstab) by default.  This option  can
              be  used  together  with  the  -f flag for already canonicalized
              absolute paths.  The option is designed for mount helpers  which
              call  mount -i.  It is strongly recommended to not use this com-
              mand-line option for normal mount operations.

              Note  that  mount(8)  does  not  pass   this   option   to   the
              /sbin/mount.type helpers.

       -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 an existing  record  in
              /etc/mtab and fails when the record already exists (with a regu-
              lar non-fake mount, this check is done by the kernel).

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

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

       -l, --show-labels
              Add the labels in the mount output.  mount must have  permission
              to  read  the  disk device (e.g. be suid root) for this to work.
              One can set such a label  for  ext2,  ext3  or  ext4  using  the
              e2label(8)  utility, or for XFS using xfs_admin(8), or for reis-
              erfs using reiserfstune(8).

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

       -n, --no-mtab
              Mount without writing in /etc/mtab.  This is necessary for exam-
              ple when /etc is on a read-only filesystem.

       -O, --test-opts opts
              Limit the set of filesystems to which the -a option applies.  In
              this regard it is like the -t option except that -O  is  useless
              without -a.  For example, the command:

                     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
              rest.

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

                     mount -a -t ext2 -O _netdev

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

       -o, --options opts
              Use  the specified mount options.  The opts argument is a comma-
              separated list.  For example:

                     mount LABEL=mydisk -o noatime,nodev,nosuid

              For more details, see the FILESYSTEM-INDEPENDENT  MOUNT  OPTIONS
              and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.

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

       -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 exam-
              ple, ext3 and ext4 will replay the journal if the filesystem  is
              dirty.   To  prevent  this kind of write access, you may want to
              mount an ext3  or  ext4  filesystem  with  the  ro,noload  mount
              options  or  set  the block device itself to read-only mode, see
              the blockdev(8) command.

       -s     Tolerate sloppy mount options rather than  failing.   This  will
              ignore  mount  options  not supported by a filesystem type.  Not
              all filesystems support this option.  Currently  it's  supported
              by the mount.nfs mount helper only.

       --source device
              If  only  one  argument  for the mount command is given then the
              argument might be interpreted as target (mountpoint)  or  source
              (device).   This  option  allows  to  explicitly define that the
              argument is the mount source.

       --target directory
              If only one argument for the mount command  is  given  then  the
              argument  might  be interpreted as target (mountpoint) or source
              (device).  This option allows  to  explicitly  define  that  the
              argument is the mount target.

       -T, --fstab path
              Specifies  an  alternative  fstab  file.  If path is a directory
              then the files in the directory  are  sorted  by  strverscmp(3);
              files  that  start  with  "." or without an .fstab extension are
              ignored.  The option can be  specified  more  than  once.   This
              option  is mostly designed for initramfs or chroot scripts where
              additional configuration is  specified  beyond  standard  system
              configuration.

              Note  that  mount(8)  does  not  pass  the option --fstab to the
              /sbin/mount.type helpers, meaning  that  the  alternative  fstab
              files will be invisible for the helpers.  This is no problem for
              normal mounts, but user (non-root) mounts always  require  fstab
              to verify the user's rights.

       -t, --types fstype
              The argument following the -t is used to indicate the filesystem
              type.  The filesystem types which are currently supported depend
              on  the  running  kernel.   See  /proc/filesystems and /lib/mod-
              ules/$(uname -r)/kernel/fs for a complete list of  the  filesys-
              tems.   The  most common are ext2, ext3, ext4, xfs, btrfs, vfat,
              sysfs, proc, nfs and cifs.

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

              If no -t option is given, or if  the  auto  type  is  specified,
              mount  will try to guess the desired type.  Mount uses the blkid
              library for guessing the filesystem type; if that does not  turn
              up anything that looks familiar, mount will try to read the file
              /etc/filesystems, or, if that does not exist, /proc/filesystems.
              All  of  the filesystem types listed there will be tried, except
              for those that are labeled "nodev" (e.g., devpts, proc and nfs).
              If  /etc/filesystems  ends in a line with a single *, mount will
              read /proc/filesystems afterwards.  While trying, all filesystem
              types will be mounted with the mount option silent.

              The auto type may be useful for user-mounted floppies.  Creating
              a file /etc/filesystems can be useful to change the probe  order
              (e.g.,  to  try vfat before msdos or ext3 before ext2) or if you
              use a kernel module autoloader.

              More than one type may be specified in a  comma-separated  list,
              for  option  -t  as well as in an /etc/fstab entry.  The list of
              filesystem types for option -t can be prefixed with no to  spec-
              ify  the  filesystem  types  on which no action should be taken.
              The prefix no has no effect  when  specified  in  an  /etc/fstab
              entry.

              The  prefix  no can be meaningful with the -a option.  For exam-
              ple, the command

                     mount -a -t nomsdos,smbfs

              mounts all filesystems except those of type msdos and smbfs.

              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) an ad hoc code is necessary.  The nfs, nfs4,
              cifs, smbfs, and ncpfs filesystems have a  separate  mount  pro-
              gram.  In order to make it possible to treat all types in a uni-
              form way, mount will execute the  program  /sbin/mount.type  (if
              that  exists)  when called with type type.  Since different ver-
              sions of the smbmount program  have  different  calling  conven-
              tions, /sbin/mount.smbfs may have to be a shell script that sets
              up the desired call.

       -U, --uuid uuid
              Mount the partition that has the specified uuid.

       -v, --verbose
              Verbose mode.

       -w, --rw, --read-write
              Mount the filesystem read/write.  This is the default.   A  syn-
              onym is -o rw.

       -V, --version
              Display version information and exit.

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

FILESYSTEM-INDEPENDENT MOUNT OPTIONS
       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
       filesystems).

       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 an 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 the noatime feature, so the inode access time is con-
              trolled by kernel defaults.  See also the  descriptions  of  the
              strictatime and relatime mount options.

       noatime
              Do  not  update inode access times on this filesystem (e.g., for
              faster access on the news spool to speed up news servers).  This
              works  for all inode types (directories too), so implies nodira-
              time.

       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-
       text=context
              The context= option is useful when mounting filesystems that  do
              not  support  extended attributes, such as a floppy or hard disk
              formatted with VFAT, or systems that are  not  normally  running
              under SELinux, such as an ext3 formatted disk from a non-SELinux
              workstation.  You can also use context= on  filesystems  you  do
              not  trust,  such  as  a floppy.  It also helps in compatibility
              with xattr-supporting filesystems on earlier 2.4.<x> kernel ver-
              sions.   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 context="sys-
              tem_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, regardless of
              their xattr support.  The fscontext option sets the  overarching
              filesystem  label to a specific security context.  This filesys-
              tem label is separate from the individual labels on  the  files.
              It represents the entire filesystem for certain kinds of permis-
              sion checks, such as during mount or file creation.   Individual
              file  labels  are  still  obtained  from the xattrs on the files
              themselves.  The context option actually sets the aggregate con-
              text  that fscontext provides, in addition to supplying the same
              label for 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  filesystem  that
              supports xattr labeling.

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

              Note that the kernel rejects any remount request  that  includes
              the  context  option,  even when unchanged from the current con-
              text.

              Warning: the context value might contain commas, in  which  case
              the  value  has  to  be properly quoted, otherwise mount(8) will
              interpret the comma as a separator between mount options.  Don't
              forget  that the shell strips off quotes and thus double quoting
              is required.  For example:

                     mount -t tmpfs none /mnt -o \
                     'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'

              For more details, see selinux(8).

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

              Note  that  the real set of all default mount options depends on
              kernel and filesystem type.  See the beginning 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
              system.

       diratime
              Update directory inode access times on this filesystem.  This is
              the  default.   Directory inode will not be updated when noatime
              is set, regardless of this option.

       nodiratime
              Do not update directory inode access times on  this  filesystem.
              If noatime option is set, this option is not needed.

       dirsync
              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  permit  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 user to mount the filesystem if  one  of  that
              user's  groups  matches  the  group  of the device.  This option
              implies the options nosuid and nodev (unless overridden by  sub-
              sequent options, as in the option line group,dev,suid).

       iversion
              Every  time  the  inode is modified, the i_version field will be
              incremented.

       noiversion
              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

       _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).

       nofail Do not report errors for this device if it does not exist.

       relatime
              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  it doesn't break mutt or other applications that need
              to know if a file has been read since the last time it was modi-
              fied.)

              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.

       norelatime
              Do not use the relatime feature.  See also the strictatime mount
              option.

       strictatime
              Allows to explicitly request full atime updates.  This makes  it
              possible  for  the  kernel to default to relatime or noatime but
              still allow userspace to override it.  For  more  details  about
              the default system mount options see /proc/mounts.

       nostrictatime
              Use the kernel's default behavior for inode access time updates.

       lazytime
              Only update times (atime, mtime, ctime) on the in-memory version
              of the file inode.

              This mount option significantly reduces writes to the inode  ta-
              ble  for workloads that perform frequent random writes to preal-
              located files.

              The on-disk timestamps are updated only when:

              - the inode needs to be updated for  some  change  unrelated  to
              file timestamps

              - the application employs fsync(2), syncfs(2), or sync(2)

              - an undeleted inode is evicted from memory

              - more than 24 hours have passed since the i-node was written to
              disk.

       nolazytime
              Do not use the lazytime feature.

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

       nosuid Do not allow set-user-identifier or set-group-identifier bits to
              take effect.

       silent Turn on the silent flag.

       loud   Turn off the silent flag.

       owner  Allow an ordinary user to mount the filesystem if that  user  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 filesystem.  This is com-
              monly used to change the mount flags  for  a  filesystem,  espe-
              cially  to  make  a  readonly  filesystem writable.  It does not
              change device or mount point.

              The remount functionality follows the  standard  way  the  mount
              command  works  with  options  from  fstab.  This means that the
              mount command only doesn't read fstab (or mtab)  when  both  the
              device and dir are specified.

              mount -o remount,rw /dev/foo /dir

              After this call all old mount options are replaced and arbitrary
              stuff from fstab (or mtab) is ignored, except the  loop=  option
              which  is  internally generated and maintained by the mount com-
              mand.

              mount -o remount,rw  /dir

              After this call mount reads fstab and merges these options  with
              the  options  from the command line (-o). If no mountpoint found
              in fstab than remount with unspecified source is allowed.

       ro     Mount the filesystem read-only.

       rw     Mount the filesystem read-write.

       sync   All I/O to the filesystem should be done synchronously.  In  the
              case  of  media with a 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 the mtab file (or to the private
              libmount file in /run/mount on systems without a  regular  mtab)
              so  that  this same user 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 user to mount the filesystem.   This  is  the
              default; it does not imply any other options.

       users  Allow any user to mount and to unmount the filesystem, even when
              some other ordinary user mounted it.  This  option  implies  the
              options  noexec,  nosuid, and nodev (unless overridden by subse-
              quent options, as in the option line users,exec,dev,suid).

       x-*    All options prefixed with "x-" are interpreted as comments or as
              userspace  application-specific  options.  These options are not
              stored in the mtab file, nor sent to the mount.type helpers  nor
              to  the  mount(2)  system  call.  The suggested format is x-app-
              name.option (e.g. x-systemd.automount).

       x-mount.mkdir[=mode]
              Allow to make a target  directory  (mountpoint).   The  optional
              argument  mode  specifies  the  filesystem  access mode used for
              mkdir(2) in octal notation.  The default  mode  is  0755.   This
              functionality is supported only for root users.

FILESYSTEM-SPECIFIC MOUNT OPTIONS
       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-
       tion/filesystems.

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

       ownmask=value and othmask=value
              Set the permission mask for ADFS 'owner' permissions and 'other'
              permissions,  respectively  (default:  0700  and  0077,  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 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.

       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  filesys-
              tem.

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

       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 btrfs
       Btrfs is a copy-on-write filesystem for  Linux  aimed  at  implementing
       advanced  features  while focusing on fault tolerance, repair, and easy
       administration.

       alloc_start=bytes
              Debugging option to force all block allocations above a  certain
              byte  threshold on each block device.  The value is specified in
              bytes, optionally with a K, M, or G  suffix,  case  insensitive.
              Default is 1MB.

       autodefrag
              Disable/enable   auto   defragmentation.   Auto  defragmentation
              detects small random writes into files and queues  them  up  for
              the defrag process.  Works best for small files; not well-suited
              for large database workloads.

       check_int|check_int_data|check_int_print_mask=value
              These debugging options control the behavior  of  the  integrity
              checking   module(the   BTRFS_FS_CHECK_INTEGRITY  config  option
              required).

              check_int enables the integrity checker module,  which  examines
              all  block-write  requests  to  ensure on-disk consistency, at a
              large memory and CPU cost.

              check_int_data includes extent data in the integrity checks, and
              implies the check_int option.

              check_int_print_mask  takes  a  bitmask  of BTRFSIC_PRINT_MASK_*
              values as defined in fs/btrfs/check-integrity.c, to control  the
              integrity checker module behavior.

              See  comments  at the top of fs/btrfs/check-integrity.c for more
              info.

       commit=seconds
              Set the interval of periodic  commit,  30  seconds  by  default.
              Higher values defer data being synced to permanent storage, with
              obvious consequences when the system crashes.  The  upper  bound
              is  not  forced,  but a warning is printed if it's more than 300
              seconds (5 minutes).

       compress|compress=type|compress-force|compress-force=type
              Control BTRFS file data compression.  Type may be  specified  as
              "zlib"  "lzo" or "no" (for no compression, used for remounting).
              If no type is specified, zlib is  used.   If  compress-force  is
              specified,  all  files  will  be compressed, whether or not they
              compress well.  If compression is enabled, nodatacow and nodata-
              sum are disabled.

       degraded
              Allow  mounts  to  continue  with missing devices.  A read-write
              mount may fail with too many devices missing, for example  if  a
              stripe member is completely missing.

       device=devicepath
              Specify  a  device  during  mount  so that ioctls on the control
              device can be avoided.  Especially useful when trying to mount a
              multi-device setup as root.  May be specified multiple times for
              multiple devices.

       discard
              Disable/enable the discard mount option.  The  discard  function
              issues  frequent  commands to let the block device reclaim space
              freed by the filesystem.  This is useful for SSD devices, thinly
              provisioned LUNs and virtual machine images, but may have a sig-
              nificant performance impact.  (The fstrim command is also avail-
              able to initiate batch trims from userspace.)

       enospc_debug
              Disable/enable  debugging  option  to  be  more  verbose in some
              ENOSPC conditions.

       fatal_errors=action
              Action to take when encountering a fatal error:
                "bug" - BUG() on a fatal error.  This is the default.
                "panic" - panic() on a fatal error.

       flushoncommit
              The flushoncommit mount option forces  any  data  dirtied  by  a
              write  in  a  prior transaction to commit as part of the current
              commit.  This makes the committed state a fully consistent  view
              of  the  filesystem from the application's perspective (i.e., it
              includes all completed filesystem operations).  This was  previ-
              ously the behavior only when a snapshot is created.

       inode_cache
              Enable  free  inode  number caching.   Defaults to off due to an
              overflow problem when the free space CRCs  don't  fit  inside  a
              single page.

       max_inline=bytes
              Specify  the  maximum  amount  of  space,  in bytes, that can be
              inlined in a metadata B-tree leaf.  The value  is  specified  in
              bytes,  optionally  with  a K, M, or G suffix, case insensitive.
              In practice, this value is limited by the root sector size, with
              some  space  unavailable  due to leaf headers.  For a 4k sector-
              size, max inline data is ~3900 bytes.

       metadata_ratio=value
              Specify that 1 metadata chunk should be  allocated  after  every
              value data chunks.  Off by default.

       noacl  Enable/disable  support  for  Posix Access Control Lists (ACLs).
              See the acl(5) manual page for more information about ACLs.

       nobarrier
              Enable/disable the use of  block-layer  write  barriers.   Write
              barriers  ensure  that  certain  IOs  make it through the device
              cache and are on persistent storage.  If disabled  on  a  device
              with  a  volatile  (non-battery-backed)  write-back  cache,  the
              nobarrier option will lead to filesystem corruption on a  system
              crash or power loss.

       nodatacow
              Enable/disable data copy-on-write for newly created files.  This
              option implies nodatasum, and disables all compression.

       nodatasum
              Enable/disable data checksumming for newly created files.   This
              option implies datacow.

       notreelog
              Enable/disable  the  tree  logging  used  for  fsync  and O_SYNC
              writes.

       recovery
              Enable autorecovery attempts if a bad  tree  root  is  found  at
              mount  time.   Currently  this  scans a list of several previous
              tree roots and tries to use the first readable.

       rescan_uuid_tree
              Force check and rebuild procedure of the UUID tree.  This should
              not normally be needed.

       skip_balance
              Skip  automatic resume of an interrupted balance operation after
              mount.  May be resumed with "btrfs balance resume."

       nospace_cache
              Disable freespace cache loading without clearing the cache.

       clear_cache
              Force clearing and rebuilding of the disk space cache  if  some-
              thing has gone wrong.

       ssd|nossd|ssd_spread
              Options  to  control  ssd allocation schemes.  By default, BTRFS
              will enable or disable ssd allocation  heuristics  depending  on
              whether  a  rotational or nonrotational disk is in use.  The ssd
              and nossd options can override this autodetection.

              The ssd_spread mount option attempts to allocate into big chunks
              of  unused  space,  and  may  perform  better  on  low-end ssds.
              ssd_spread implies ssd, enabling all  other  ssd  heuristics  as
              well.

       subvol=path
              Mount  subvolume  at  path  rather than the root subvolume.  The
              path is relative to the top level subvolume.

       subvolid=ID
              Mount subvolume specified by an ID number rather than  the  root
              subvolume.   This allows mounting of subvolumes which are not in
              the root of the mounted filesystem.  You can use "btrfs  subvol-
              ume list" to see subvolume ID numbers.

       subvolrootid=objectid  (deprecated)
              Mount  subvolume specified by objectid rather than the root sub-
              volume.  This allows mounting of subvolumes which are not in the
              root  of  the  mounted filesystem.  You can use "btrfs subvolume
              show " to see the object ID for a subvolume.

       thread_pool=number
              The number of worker threads to allocate.  The default number is
              equal to the number of CPUs + 2, or 8, whichever is smaller.

       user_subvol_rm_allowed
              Allow  subvolumes  to  be  deleted by a non-root user.  Use with
              caution.

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
       None.

Mount options for debugfs
       The debugfs filesystem is a pseudo filesystem, traditionally mounted on
       /sys/kernel/debug.  As of kernel version 3.4, debugfs has the following
       options:

       uid=n, gid=n
              Set the owner and group of the mountpoint.

       mode=value
              Sets the mode of the mountpoint.

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

       newinstance
              Create  a  private  instance  of  devpts  filesystem,  such that
              indices of ptys allocated in this new instance  are  independent
              of indices created in other instances of devpts.

              All  mounts  of devpts without this newinstance option share the
              same set of pty indices (i.e legacy mode).  Each mount of devpts
              with the newinstance option has a private set of pty indices.

              This  option  is  mainly used to support containers in the linux
              kernel.  It is implemented in  linux  kernel  versions  starting
              with  2.6.29.   Further, this mount option is valid only if CON-
              FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel  configu-
              ration.

              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.

       ptmxmode=value

              Set the mode for the new ptmx device node in the devpts filesys-
              tem.

              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-
              ration.

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).

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

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

              % mount /k -o minixdf; df /k; umount /k

              Filesystem  1024-blocks   Used  Available  Capacity  Mounted on
              /dev/sda6     2630655    86954   2412169      3%     /k

              % mount /k -o bsddf; df /k; umount /k

              Filesystem  1024-blocks  Used  Available  Capacity  Mounted on
              /dev/sda6     2543714      13   2412169      0%     /k

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

       check=none or nocheck
              No  checking  is done at mount time.  This is the default.  This
              is fast.  It is wise to invoke e2fsck(8)  every  now  and  then,
              e.g.  at  boot  time.   The  non-default behavior is unsupported
              (check=normal and check=strict options have been removed).  Note
              that these mount options don't have to be supported if ext4 ker-
              nel driver is used for ext2 and ext3 filesystems.

       debug  Print debugging info upon each (re)mount.

       errors={continue|remount-ro|panic}
              Define the behavior  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.

       grpquota|noquota|quota|usrquota
              The  usrquota  (same  as  quota) mount option enables user quota
              support on the filesystem.  grpquota enables group  quotas  sup-
              port.   You need the quota utilities to actually enable and man-
              age the quota system.

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

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

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

       journal=update
              Update the ext3 filesystem'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 filesystem's journal file; ext3 will create a new jour-
              nal, overwriting the old contents of the file whose inode number
              is inum.

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

       norecovery/noload
              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.

       data={journal|ordered|writeback}
              Specifies the journaling mode for file data.  Metadata is always
              journaled.  To use modes other than ordered on the root filesys-
              tem,  pass  the mode to the kernel as boot parameter, e.g. root-
              flags=data=journal.

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

              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 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.

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

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

       barrier=0 / barrier=1
              This disables / enables the use of write  barriers  in  the  jbd
              code.   barrier=0  disables,  barrier=1 enables (default).  This
              also requires an IO stack which can support barriers, and if jbd
              gets an error on a barrier write, it will disable barriers again
              with a warning.  Write barriers enforce proper on-disk  ordering
              of  journal  commits,  making volatile disk write caches safe to
              use, at some performance penalty.  If your  disks  are  battery-
              backed  in  one  way  or  another, disabling barriers may safely
              improve performance.

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

       user_xattr
              Enable Extended User Attributes.  See the attr(5) manual page.

       acl    Enable POSIX Access Control Lists.  See the acl(5) manual page.

       usrjquota=aquota.user|grpjquota=aquota.group|jqfmt=vfsv0
              Apart  from  the  old quota system (as in ext2, jqfmt=vfsold aka
              version 1 quota) ext3 also supports journaled quotas (version  2
              quota).   jqfmt=vfsv0  enables  journaled quotas.  For journaled
              quotas   the    mount    options    usrjquota=aquota.user    and
              grpjquota=aquota.group  are  required  to  tell the quota system
              which quota database files to use.  Journaled  quotas  have  the
              advantage that even after a crash no quota check is required.

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

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

       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_checksum' internally.

       barrier=0 / barrier=1 / barrier / nobarrier
              These mount options have the same effect as in ext3.  The  mount
              options "barrier" and "nobarrier" are added for consistency with
              other ext4 mount options.

              The ext4 filesystem enables write barriers by default.

       inode_readahead_blks=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 value must be a  power  of  2.   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 filesystem
              blocks.

       delalloc
              Deferring block allocation until write-out time.

       nodelalloc
              Disable delayed allocation.  Blocks are allocated 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  transaction  has been running is less than the commit
              time, ext4 will try sleeping for the commit time to see if other
              operations will join the transaction.  The commit time is capped
              by the max_batch_time, which defaults to 15000 us (15 ms).  This
              optimization   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  priority)
              which  should be used for I/O operations submitted by kjournald2
              during a commit operation.  This  defaults  to  3,  which  is  a
              slightly higher priority than the default I/O priority.

       abort  Simulate  the effects of calling ext4_abort() for debugging pur-
              poses.  This is normally  used  while  remounting  a  filesystem
              which is already mounted.

       auto_da_alloc|noauto_da_alloc
              Many broken applications don't use fsync() when replacing exist-
              ing 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 committed.  This provides roughly the same level of
              guarantees  as  ext3,  and avoids the "zero-length" problem that
              can happen when a system crashes before the  delayed  allocation
              blocks are forced to disk.

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

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

       discard/nodiscard
              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.

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

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

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

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

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

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

       blocksize={512|1024|2048}
              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.)

       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.

       allow_utime=value
              This option controls the permission check of mtime/atime.

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

              2      Other users can change timestamp.

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

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

       check=value
              Three different levels of pickiness 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 that contain long parts or spe-
                     cial characters that are sometimes used on Linux but  are
                     not accepted by MS-DOS (+, =, etc.) are rejected.

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

       conv=mode
              The fat filesystem can  perform  CRLF<-->NL  conversion  (MS-DOS
              text  format  to UNIX text format) in the kernel.  The following
              conversion modes are available:

              b[inary]
                     No translation is performed.  This is the default.

              t[ext] CRLF<-->NL translation is performed on all files.

              a[uto] 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 filesystems mounted in binary mode, a conversion tool (from-
              dos/todos) is available.  This option is obsolete.

       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.  This option is obsolete.

       cvf_option=option
              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).

       discard
              If  set,  causes discard/TRIM commands to be issued to the block
              device when blocks are freed.  This is useful  for  SSD  devices
              and sparse/thinly-provisioned LUNs.

       dos1xfloppy
              If  set,  use a fallback default BIOS Parameter Block configura-
              tion, determined by backing device size. These static parameters
              match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB,
              and 360 kiB floppies and floppy images.

       errors={panic|continue|remount-ro}
              Specify FAT behavior on critical errors: panic, continue without
              doing  anything,  or  remount  the  partition  in read-only mode
              (default behavior).

       fat={12|16|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
              filenames are stored on disk in Unicode format.

       nfs={stale_rw|nostale_ro}
              Enable  this  only if you want to export the FAT filesystem over
              NFS.

              stale_rw: This option maintains an index  (cache)  of  directory
              inodes  which  is  used by the nfs-related code to improve look-
              ups. Full file operations (read/write) over  NFS  are  supported
              but with cache eviction at NFS server, this could result in spu-
              rious ESTALE errors.

              nostale_ro: This option bases the inode number and filehandle on
              the on-disk location of a file in the FAT directory entry.  This
              ensures that ESTALE will not be returned after a file is evicted
              from  the inode cache. However, it means that operations such as
              rename, create and unlink could cause  filehandles  that  previ-
              ously  pointed  at one file to point at a different file, poten-
              tially causing data corruption. For  this  reason,  this  option
              also mounts the filesystem readonly.

              To  maintain  backward compatibility, '-o nfs' is also accepted,
              defaulting to stale_rw.

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

       time_offset=minutes
              Set offset for conversion of timestamps from local time used  by
              FAT  to UTC.  I.e., minutes minutes will be subtracted from each
              timestamp to convert it to UTC used internally by Linux. This is
              useful  when the time zone set in the kernel via settimeofday(2)
              is not the time zone used by  the  filesystem.  Note  that  this
              option  still  does not provide correct time stamps in all cases
              in presence of DST - time stamps in a different DST setting will
              be off by one hour.

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

       rodir  FAT has the  ATTR_RO  (read-only)  attribute.  On  Windows,  the
              ATTR_RO  of the directory will just be ignored, and is used only
              by applications as a flag (e.g.  it's  set  for  the  customized
              folder).

              If you want to use ATTR_RO as read-only flag even for the direc-
              tory, set this option.

       showexec
              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.

       sys_immutable
              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.

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

       conv={binary|text|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 filesys-
       tem (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]|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 filesystem the indicated user or group id,
              possibly overriding the information  found  in  the  Rock  Ridge
              extensions.  (Default: uid=0,gid=0.)

       map={n[ormal]|o[ff]|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 and execute  permission  for  everybody.)   Since
              Linux 2.1.37 one no longer needs to specify the mode in decimal.
              (Octal is indicated by a leading 0.)

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

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

       conv={a[uto]|b[inary]|m[text]|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 16 MB.

       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 ends.

       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|remount-ro|panic}
              Define the behavior  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.)

       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 filesystem detects an incon-
       sistency, it reports an error and sets the file system read-only.   The
       filesystem can be made writable again by remounting it.

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

Mount options for nfs and nfs4
       See the options section of the nfs(5) man page (nfs-utils package  must
       be installed).

       The  nfs  and  nfs4  implementation expects a binary argument (a struct
       nfs_mount_data) to the mount system call.  This argument is constructed
       by  mount.nfs(8)  and the current version of mount (2.13) does not know
       anything about nfs and nfs4.

Mount options for ntfs
       iocharset=name
              Character set to use when returning file  names.   Unlike  VFAT,
              NTFS  suppresses  names  that contain nonconvertible 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 filesystem distinguishes between upper
              and lower case.  The 8.3 alias names are presented as hard links
              instead of being suppressed.  This option is obsolete.

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

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

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

Mount options for reiserfs
       Reiserfs is a journaling filesystem.

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

       hash={rupasov|tea|r5|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 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-
                     tem.

       hashed_relocation
              Tunes  the  block  allocator.   This  may  provide   performance
              improvements in some situations.

       no_unhashed_relocation
              Tunes   the  block  allocator.   This  may  provide  performance
              improvements 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  journaling.   This  will  provide  slight   performance
              improvements in some situations at the cost of losing reiserfs's
              fast recovery from crashes.  Even with this  option  turned  on,
              reiserfs  still  performs  all  journaling  operations, save for
              actual writes into its journaling area.  Implementation of nolog
              is a work in progress.

       notail By  default,  reiserfs  stores  small  files  and  `file  tails'
              directly into its tree.  This confuses some  utilities  such  as
              LILO(8).   This  option is used to disable packing of files into
              the tree.

       replayonly
              Replay the transactions which are in the  journal,  but  do  not
              actually mount the filesystem.  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.

       user_xattr
              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 disables / enables the use of write barriers in  the  jour-
              naling   code.   barrier=none  disables,  barrier=flush  enables
              (default).  This also requires an IO  stack  which  can  support
              barriers,  and  if reiserfs gets an error on a barrier write, it
              will disable barriers again  with  a  warning.   Write  barriers
              enforce  proper  on-disk  ordering  of  journal  commits, making
              volatile disk write caches safe  to  use,  at  some  performance
              penalty.   If  your  disks  are  battery-backed  in  one  way or
              another, disabling barriers may safely improve performance.

Mount options for romfs
       None.

Mount options for squashfs
       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
       size=nbytes
              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%

       nr_blocks=
              The same as size, but in blocks of PAGE_CACHE_SIZE

       nr_inodes=
              The maximum number of inodes for this instance.  The default  is
              half  of the number of your physical RAM pages, or (on a machine
              with highmem) the number of lowmem RAM pages, whichever  is  the
              lower.

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

       mode=  Set initial permissions of the root directory.

       uid=   The user id.

       gid=   The group id.

       mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
              Set  the  NUMA  memory  allocation  policy for all files in that
              instance (if the kernel CONFIG_NUMA is enabled) - which  can  be
              adjusted on the fly via 'mount -o remount ...'

              default
                     prefers to allocate memory from the local node

              prefer:Node
                     prefers to allocate memory from the given Node

              bind:NodeList
                     allocates memory only from nodes in NodeList

              interleave
                     prefers to allocate from each node in turn

              interleave:NodeList
                     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-minus"-separated  decimal
              numbers,  the  smallest  and  largest node numbers in the range.
              For example, mpol=bind:0-3,5,7,9-15

              Note that trying to mount a tmpfs with an mpol option will  fail
              if  the  running  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

              ubiX:NAME
                     UBI device number X, volume with name NAME

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

       The following mount options are available:

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

       no_bulk_read
              Do not bulk-read.  This is the default.

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

       no_chk_data_crc.
              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.

       compr={none|lzo|zlib}
              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.

       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 filesystem widely used in different operating systems.
              The problem are differences among implementations.  Features  of
              some  implementations are undocumented, so its hard to recognize
              the type of ufs automatically.  That's why the user must specify
              the type of ufs by mount option.  Possible values are:

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

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

              ufs2   Used in FreeBSD 5.x supported as read-write.

              5xbsd  Synonym for ufs2.

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

              hp     For filesystems created by HP-UX, read-only.

              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 behavior 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 invalid on the vfat filesystem.
              The escape sequence that gets used, where u is the Unicode char-
              acter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).

       posix  Allow  two  files  with  names  that  only differ in case.  This
              option is obsolete.

       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 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=mode
              Defines the behavior for creation and display of filenames which
              fit  into  8.3 characters.  If a long name for a file exists, it
              will always be the preferred one for 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 short name as is; store a long name when the
                     short name is not all lower case or all upper case.

              mixed  Display the short name as is; store a long name when  the
                     short  name  is  not  all  upper  case.  This mode is the
                     default since Linux 2.6.32.

Mount options for usbfs
       devuid=uid and devgid=gid and devmode=mode
              Set the owner and group and mode of  the  device  files  in  the
              usbfs  filesystem  (default: uid=gid=0, mode=0644).  The mode is
              given in octal.

       busuid=uid and busgid=gid and busmode=mode
              Set the owner and group and mode of the bus directories  in  the
              usbfs  filesystem  (default: uid=gid=0, mode=0555).  The mode is
              given in octal.

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

Mount options for xenix
       None.

Mount options for xfs
       See  the  options section of the xfs(5) man page (xfsprogs package must
       be installed).

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

              mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3

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

       If no explicit loop device is mentioned (but just an option  `-o  loop'
       is  given), then mount will try to find some unused loop device and use
       that, for example

              mount /tmp/disk.img /mnt -o loop

       The mount command automatically creates a loop device  from  a  regular
       file  if  a filesystem type is not specified or the filesystem is known
       for libblkid, for example:

              mount /tmp/disk.img /mnt

              mount -t ext3 /tmp/disk.img /mnt

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

       Since Linux 2.6.25 auto-destruction of loop devices is supported, mean-
       ing  that  any  loop  device allocated by mount will be freed by umount
       independently of /etc/mtab.

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

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

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

       The command mount -a returns 0 (all succeeded), 32 (all failed), or  64
       (some failed, some succeeded).

EXTERNAL HELPERS
       The syntax of external mount helpers is:

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

       where the suffix is the filesystem type and the -sfnvo options have the
       same  meaning  as  the normal mount options.  The -t option is used for
       filesystems with subtypes  support  (for  example  /sbin/mount.fuse  -t
       fuse.sshfs).

       The  command mount does not pass the mount options unbindable, runbind-
       able, private, rprivate, slave, rslave, shared, rshared, auto,  noauto,
       comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers.
       All other options are used in a comma-separated list as argument to the
       -o option.

FILES
       /etc/fstab        filesystem table

       /etc/mtab         table of mounted filesystems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try

ENVIRONMENT
       LIBMOUNT_FSTAB=<path>
              overrides  the  default  location of the fstab file (ignored for
              suid)

       LIBMOUNT_MTAB=<path>
              overrides the default location of the  mtab  file  (ignored  for
              suid)

       LIBMOUNT_DEBUG=all
              enables libmount debug output

       LIBBLKID_DEBUG=all
              enables libblkid debug output

       LOOPDEV_DEBUG=all
              enables loop device setup debug output

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

BUGS
       It is possible for a corrupted filesystem to cause a crash.

       Some  Linux filesystems don't support -o sync and -o dirsync (the ext2,
       ext3, fat and vfat filesystems do support  synchronous  updates  (a  la
       BSD) when mounted with the sync option).

       The  -o remount may not be able to change mount parameters (all ext2fs-
       specific parameters, except sb, are  changeable  with  a  remount,  for
       example, but you can't change gid or umask for the fatfs).

       It  is  possible  that  files /etc/mtab and /proc/mounts don't match on
       systems with regular mtab file. 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 particu-
       lar  case  the mount command may reports unreliable information about a
       NFS mount point and the /proc/mounts file usually contains  more  reli-
       able  information.)  This  is  another reason to replace mtab file with
       symlink to the /proc/mounts file.

       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.

       The loop option with the offset or sizelimit options used may fail when
       using older kernels if the mount command can't confirm that the size of
       the  block device has been configured as requested.  This situation can
       be worked around by using the losetup command manually  before  calling
       mount with the configured loop device.

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

AUTHORS
       Karel Zak <kzak@redhat.com>

AVAILABILITY
       The  mount  command  is part of the util-linux package and is available
       from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux                         July 2014                          MOUNT(8)