Provided by: mount_2.27.1-6ubuntu2_i386 bug


       mount - mount a filesystem


       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


       All files accessible in a Unix system are arranged in one big tree, the
       file hierarchy, rooted at /.   These  files  can  be  spread  out  over
       several  devices.   The  mount  command serves to attach the filesystem
       found on some device to the big file tree.  Conversely,  the  umount(8)
       command will detach it again.

       The standard form of the mount command is:

              mount -t type device dir

       This  tells  the kernel to attach the filesystem found on device (which
       is of type type) at the directory dir.  The previous contents (if  any)
       and  owner  and  mode  of  dir  become  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

              mount --target /mountpoint

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

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

              The following command lists all  mounted  filesystems  (of  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
      It is also  possible  to  indicate  a  block
              special  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
              portable.  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

              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

              When mounting a  filesystem  mentioned  in  fstab  or  mtab,  it
              suffices 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
              filesystems 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

              The mount program does not read  the  /etc/fstab  file  if  both
              device  (or  LABEL,  UUID,  PARTUUID  or  PARTLABEL) and dir are
              specified.  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


                     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
              implemented 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

              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
              submounts  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
              master,  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
              preceding  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


       The full set of mount  options  used  by  an  invocation  of  mount  is
       determined  by  first  extracting  the mount options for the filesystem
       from the fstab table, then applying any options  specified  by  the  -o
       argument, and finally applying a -r or -w option, when 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
              command-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
              determine  what  the mount command is trying to do.  It can also
              be used to add entries for devices  that  were  mounted  earlier
              with the -n option.  The -f option checks for an existing record
              in /etc/mtab and fails when the record already  exists  (with  a
              regular 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
              reiserfs 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
              example 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
              _netdev specified in the options field in the /etc/fstab file.

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

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

                     mount -a -t ext2 -O _netdev

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

       -o, --options opts
              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
              example, 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

              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/modules/$(uname  -r)/kernel/fs  for  a complete list of the
              filesystems.  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
              '' 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
              specify the filesystem types on which no action should be taken.
              The  prefix  no  has  no  effect when specified in an /etc/fstab

              The prefix no  can  be  meaningful  with  the  -a  option.   For
              example, 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
              filesystem 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
              program.  In order to make it possible to treat all types  in  a
              uniform way, mount will execute the program /sbin/mount.type (if
              that exists)  when  called  with  type  type.   Since  different
              versions   of   the  smbmount  program  have  different  calling
              conventions, /sbin/mount.smbfs may have to  be  a  shell  script
              that sets up the desired call.

       -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
              synonym is -o rw.

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

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


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

       Some  of  these  options could be enabled or disabled by default in the
       system kernel.  To  check  the  current  setting  see  the  options  in
       /proc/mounts.   Note that filesystems also have per-filesystem specific
       default mount options (see for  example  tune2fs  -l  output  for  extN

       The  following  options  apply  to any filesystem that is being mounted
       (but not every filesystem actually honors them – e.g., the sync  option
       today has 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
              controlled by kernel defaults.  See also the descriptions of the
              strictatime and relatime mount options.

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

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

              A   commonly   used    option    for    removable    media    is

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

              The fscontext= option works for all filesystems,  regardless  of
              their  xattr support.  The fscontext option sets the overarching
              filesystem  label  to  a  specific   security   context.    This
              filesystem  label  is separate from the individual labels on the
              files.  It represents the entire filesystem for certain kinds of
              permission  checks,  such  as  during  mount  or  file creation.
              Individual file labels are still obtained from the xattrs on the
              files   themselves.    The  context  option  actually  sets  the
              aggregate  context  that  fscontext  provides,  in  addition  to
              supplying the same label for individual files.

              You  can  set  the  default security context for unlabeled files
              using defcontext= option.  This  overrides  the  value  set  for
              unlabeled  files  in  the  policy and requires a 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
              visible 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

              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 \

              For more details, see selinux(8).

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

              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

              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.

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

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

       exec   Permit execution of binaries.

       noexec Do not 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
              subsequent options, as in the option line group,dev,suid).

              Every time the inode is modified, the i_version  field  will  be

              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

              Update  inode  access  times  relative to modify or change time.
              Access time is only updated if  the  previous  access  time  was
              earlier  than  the  current  modify or change time.  (Similar to
              noatime, 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

              Since Linux 2.6.30, the kernel defaults to the behavior provided
              by   this   option  (unless  noatime  was  specified),  and  the
              strictatime option is required to obtain traditional  semantics.
              In  addition, since Linux 2.6.30, the file's last access time is
              always updated if it is more than 1 day old.

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

              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.

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

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

              This  mount  option  significantly  reduces  writes to the inode
              table for workloads  that  perform  frequent  random  writes  to
              preallocated 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

              Do not use the lazytime feature.

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

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

       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).

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

              The  remount  functionality  follows  the standard way 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

              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

       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
              subsequent 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-
              appname.option (e.g. x-systemd.automount).

              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.


       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

Mount options for adfs

       uid=value and gid=value
              Set the owner and group of the files in the filesystem (default:

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

Mount options for affs

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

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

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

              Do  not  allow  any  changes  to  the  protection  bits  on  the

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

              Print an informational message for each successful mount.

              Prefix used before volume name, when following a link.

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

              (Default:  2.)  Number  of  unused  blocks  at  the start of the

              Give explicitly the location of the root block.

              Give blocksize.  Allowed values are 512, 1024, 2048, 4096.

              These  options  are  accepted  but  ignored.   (However,   quota
              utilities 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

              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.

              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.

              These  debugging  options  control the behavior of the integrity
              checking  module(the  BTRFS_FS_CHECK_INTEGRITY   config   option

              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

              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).

              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
              nodatasum are disabled.

              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.

              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.

              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
              significant  performance  impact.   (The  fstrim command is also
              available to initiate batch trims from userspace.)

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

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

              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
              previously the behavior only when a snapshot is created.

              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.

              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
              sectorsize, max inline data is ~3900 bytes.

              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.

              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.

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

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

              Enable/disable the  tree  logging  used  for  fsync  and  O_SYNC

              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.

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

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

              Disable freespace cache loading without clearing the cache.

              Force  clearing  and  rebuilding  of  the  disk  space  cache if
              something has gone wrong.

              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

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

              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
              subvolume list" to see subvolume ID numbers.

       subvolrootid=objectid  (deprecated)
              Mount subvolume specified  by  objectid  rather  than  the  root
              subvolume.   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.

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

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

Mount options for cifs

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

Mount options for coherent


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

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

              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

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

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

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

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

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

              To use this option effectively, /dev/ptmx  must  be  a  symbolic
              link  to  pts/ptmx.  See Documentation/filesystems/devpts.txt in
              the linux kernel source tree for details.


              Set the mode  for  the  new  ptmx  device  node  in  the  devpts

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

Mount options for ext2

       The  `ext2'  filesystem  is the standard Linux filesystem.  Since Linux
       2.5.46, for most  mount  options  the  default  is  determined  by  the
       filesystem superblock.  Set them with tune2fs(8).

              Support POSIX Access Control Lists (or not).

              Set  the  behavior  for  the  statfs  system  call.  The minixdf
              behavior 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
              kernel driver is used for ext2 and ext3 filesystems.

       debug  Print debugging info upon each (re)mount.

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

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

              The usrquota (same as quota) mount  option  enables  user  quota
              support  on  the  filesystem.   grpquota  enables  group  quotas
              support.  You need the quota utilities to  actually  enable  and
              manage the quota system.

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

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

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

              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:

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

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

              When  the  external  journal  device's  major/minor numbers have
              changed, 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

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

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

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

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

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

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

              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.

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

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

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

              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
     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.

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

              Commit  block  can  be  written  to  disk  without  waiting  for
              descriptor blocks.  If enabled, older kernels cannot  mount  the
              device.  This will enable 'journal_checksum' 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.

              This tuning parameter controls the maximum number of inode table
              blocks that ext4's inode table readahead algorithm will pre-read
              into  the  buffer  cache.   The value must be a power of 2.  The
              default value is 32 blocks.

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

              Deferring block allocation until write-out time.

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

              Maximum  amount  of  time  ext4  should  wait   for   additional
              filesystem  operations  to  be batch together with a synchronous
              write operation.  Since a synchronous write 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  automatically  tune  for the speed of the disk, by
              measuring the amount of time  (on  average)  that  it  takes  to
              finish  committing  a  transaction.   Call this time the "commit
              time".  If the time that the transaction  has  been  running  is
              less than the commit time, ext4 will try sleeping for the commit
              time to see if other operations will join the transaction.   The
              commit  time  is capped by the max_batch_time, which defaults to
              15000 µs (15 ms).  This optimization can be turned off  entirely
              by setting max_batch_time to 0.

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

              The  I/O priority (from 0 to 7, where 0 is the highest 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
              purposes.   This  is normally used while remounting a filesystem
              which is already mounted.

              Many  broken  applications  don't  use  fsync()  when  replacing
              existing files via patterns such as

              fd  = open("")/write(fd,...)/close(fd)/ rename("",

              or worse yet

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

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

              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.

              The lazy itable init code  will  wait  n  times  the  number  of
              milliseconds  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.

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

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

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

              Controls  whether  or  not ext4 should use the DIO read locking.
              If the dioread_nolock option is  specified  ext4  will  allocate
              uninitialized  extent before buffer write and convert the extent
              to initialized after IO completes.  This  approach  allows  ext4
              code  to  avoid using inode mutex, which improves scalability on
              high speed storages.  However  this  does  not  work  with  data
              journaling and dioread_nolock option will be ignored with kernel
              warning.  Note that dioread_nolock code path is  only  used  for
              extent-based  files.   Because  of the restrictions this options
              comprises it is off by default (e.g. dioread_lock).

              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
              environments,  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.)

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

Mount options for fat

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

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

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

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

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

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

              This option controls the permission check of mtime/atime.

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

              2      Other users can change timestamp.

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

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

              Three different levels of pickiness can be chosen:

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

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

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

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

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

                     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,

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

              For filesystems  mounted  in  binary  mode,  a  conversion  tool
              (fromdos/todos) is available.  This option is obsolete.

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

              Option passed to the CVF module.  This option is obsolete.

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

              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.

              If  set,  use  a   fallback   default   BIOS   Parameter   Block
              configuration,  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.

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

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

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

              Enable this only if you want to export the FAT  filesystem  over

              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
              spurious 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
              previously pointed at one file to point  at  a  different  file,
              potentially  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.

              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

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

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

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

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

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

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

Mount options for hfs

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

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

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

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

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

       quiet  Don't complain about invalid mount options.

Mount options for hpfs

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

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

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

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

              Do not abort mounting when certain consistency checks fail.

Mount options for iso9660

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

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

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

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

              Disable   the  use  of  Microsoft  Joliet  extensions,  even  if
              available.  Cf. map.

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

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

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

              For non-Rock Ridge volumes, give all files the  indicated  mode.
              (Default:  read  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.)

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

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

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

              Session begins from sector xxx. (Since 2.3.4.)

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

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

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

Mount options for jfs

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

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

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

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

              Define  the  behavior  when  an  error  is encountered.  (Either
              ignore  errors  and  just  mark  the  filesystem  erroneous  and
              continue, or remount the filesystem read-only, or panic and halt
              the system.)

              These options are accepted but ignored.

Mount options for minix


Mount options for msdos

       See mount  options  for  fat.   If  the  msdos  filesystem  detects  an
       inconsistency,  it reports an error and sets the file system read-only.
       The filesystem can be made writable again by remounting it.

Mount options for ncpfs

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

Mount options for nfs and nfs4

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

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

Mount options for ntfs

              Character  set  to  use when returning file names.  Unlike VFAT,
              NTFS suppresses names that  contain  nonconvertible  characters.

              New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

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

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

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

Mount options for proc

       uid=value and gid=value
              These options are recognized, but have no effect as far as I can

Mount options for ramfs

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

Mount options for reiserfs

       Reiserfs is a journaling filesystem.

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

              Choose  which  hash  function  reiserfs  will  use to find files
              within directories.

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

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

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

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

       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.

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

              A remount option which  permits  online  expansion  of  reiserfs
              partitions.   Instructs  reiserfs  to assume that the device has
              number blocks.  This option is designed  for  use  with  devices
              which  are  under  logical  volume management (LVM).  There is a
              special   resizer   utility   which   can   be   obtained   from

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

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

       barrier=none / barrier=flush
              This  disables  /  enables  the  use  of  write  barriers in the
              journaling 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


Mount options for squashfs


Mount options for smbfs

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

Mount options for sysv


Mount options for tmpfs

              Override default maximum size of the filesystem.   The  size  is
              given  in bytes, and rounded up to entire pages.  The default is
              half of the memory.  The size parameter also accepts a suffix  %
              to limit this tmpfs instance to that percentage of your physical
              RAM: the default, when neither size nor nr_blocks is  specified,
              is size=50%

              The same as size, but in blocks of PAGE_CACHE_SIZE

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

       The tmpfs mount options for sizing  (size,  nr_blocks,  and  nr_inodes)
       accept  a  suffix  k, m or g for Ki, Mi, Gi (binary kilo (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.

              Set the NUMA memory allocation policy  for  all  files  in  that
              instance  (if  the kernel CONFIG_NUMA is enabled) – which can be
              adjusted on the fly via 'mount -o remount ...'

                     prefers to allocate memory from the local node

                     prefers to allocate memory from the given Node

                     allocates memory only from nodes in NodeList

                     prefers to allocate from each node in turn

                     allocates from each node of NodeList in turn.

              The NodeList format is a comma-separated list of decimal numbers
              and  ranges,  a range being two "hyphen-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
              system relies on that tmpfs being mounted, but from time to time
              runs  a  kernel  built  without  NUMA capability (perhaps a safe
              recovery kernel),  or  with  fewer  nodes  online,  then  it  is
              advisable  to omit the mpol option from automatic mount options.
              It can be added later, when the  tmpfs  is  already  mounted  on
              MountPoint,    by    'mount    -o   remount,mpol=Policy:NodeList

Mount options for ubifs

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

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

              ubiY   UBI device number 0, volume number Y

                     UBI device number X, volume with name NAME

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

       The following mount options are available:

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

              Do not bulk-read.  This is the default.

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

              Do  not  check  data  CRC-32  checksums.   With this option, the
              filesystem does not check CRC-32 checksum for data, but it  does
              check  it  for  the  internal indexing information.  This option
              only affects reading, not writing.  CRC-32 is always  calculated
              when writing the data.

              Select  the  default compressor which is used when new files are
              written.  It is still  possible  to  read  compressed  files  if
              mounted with the none option.

Mount options for udf

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

              Show deleted files in lists.

              Unset strict conformance.

              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

              Override standard anchor location.  Default: 256.

              Override the VolumeDesc location. (unused)

              Override the PartitionDesc location. (unused)

              Set the last block of the filesystem.

              Override the fileset block location. (unused)

              Override the root directory location. (unused)

Mount options for ufs

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

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

              44bsd  For filesystems created by  a  BSD-like  system  (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.

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

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

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

              Set behavior on error:

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

                     These mount options don't do anything at present; when an
                     error is encountered only a console message is printed.

Mount options for umsdos

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

Mount options for vfat

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

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

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

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

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

              Defines the 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

              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


Mount options for xfs

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


       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,
       meaning 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.


       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).


       The syntax of external mount helpers is:

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

       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

       The   command  mount  does  not  pass  the  mount  options  unbindable,
       runbindable, 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.


       /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


              overrides  the  default  location of the fstab file (ignored for

              overrides the default location of the  mtab  file  (ignored  for

              enables libmount debug output

              enables libblkid debug output

              enables loop device setup debug output


       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)


       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
       particular  case  the  mount command may reports unreliable information
       about a NFS mount point and the /proc/mounts file usually contains more
       reliable 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

       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.


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


       Karel Zak <>


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