<root
MOUNT(8)                              System Administration                              MOUNT(8)

NAME
       mount - mount a filesystem

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

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

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

       mount [-fnrsvw] [-t fstype] [-o options] device dir

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

       The standard form of the mount command is:

              mount -t type device dir

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

       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 interpre‐
       tation of the given argument.  For example:

              mount --target /mountpoint

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

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

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

                     mount [-l] [-t type]

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

       The device indication.
              Most devices are indicated  by  a  filename  (of  a  block  special  device),  like
              /dev/sda1,  but  there are other possibilities.  For example, in the case of an NFS
              mount, device may look like knuth.cwi.nl:/dir.  It is also possible to  indicate  a
              block  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 represen‐
              tation of the UUID should be based on lower case characters.

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

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

              The command

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

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

              When mounting a filesystem mentioned in fstab or mtab, it suffices  to  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 ones.

              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 com‐
              mand

                     mount /dev/cdrom

              or

                     mount /cd

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

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

                     mount --bind olddir newdir

              or by using this fstab entry:

                     /olddir /newdir none bind

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

                     mount --bind foo foo

              The  bind mount call attaches only (part of) a single filesystem, not possible sub‐
              mounts.  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 origi‐
              nal 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 mountpoint.

              Note also that moving a mount residing under a shared mount is invalid  and  unsup‐
              ported.  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, pri‐
              vate, 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 seman‐
              tics are documented in Documentation/filesystems/sharedsubtree.txt file in the ker‐
              nel 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 neces‐
              sary 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 EXPERIMEN‐
              TAL.   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 (pri‐
              vate, slave, shared, unbindable, rprivate, rslave, rshared, runbindable).

              For example:

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

              is the same as:

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

COMMAND-LINE OPTIONS
       The full set of mount options used by an  invocation  of  mount  is  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 sec‐
       tion 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 paral‐
              lel.   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  obvi‐
              ous,  this ``fakes'' mounting the filesystem.  This option is useful in conjunction
              with the -v flag to determine what the mount command is trying to do.  It can  also
              be  used  to  add entries for devices that were mounted earlier with the -n option.
              The -f option checks for 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 rest.

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

                     mount -a -t ext2 -O _netdev

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

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

                     mount LABEL=mydisk -o noatime,nodev,nosuid

              For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and  FILESYSTEM-SPE‐
              CIFIC 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.  Cur‐
              rently 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 configu‐
              ration is specified beyond standard system configuration.

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

       -t, --types fstype
              The  argument  following  the  -t  is  used  to  indicate the filesystem type.  The
              filesystem types which are currently supported depend on the running  kernel.   See
              /proc/filesystems and /lib/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  sub‐
              type  notation  rather  than  add  any  prefix  to  the  mount  source (for example
              'sshfs#example.com' is deprecated).

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

              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  exe‐
              cute  the  program  /sbin/mount.type  (if  that exists) when called with type type.
              Since different versions of the smbmount program  have  different  calling  conven‐
              tions,  /sbin/mount.smbfs  may  have  to be a shell script that sets up the desired
              call.

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

       -v, --verbose
              Verbose mode.

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

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

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

FILESYSTEM-INDEPENDENT MOUNT OPTIONS
       Some of these options are only useful when they appear in the /etc/fstab file.

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

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

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

       atime  Do not use the noatime feature, so the inode access time is  controlled  by  kernel
              defaults.  See also the descriptions of the strictatime and relatime mount options.

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

       auto   Can be mounted with the -a option.

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

       context=context, fscontext=/context, defcontext=/context and rootcontext=context
              The context= option is  useful  when  mounting  filesystems  that  do  not  support
              extended  attributes, such as a floppy or hard disk formatted with VFAT, or systems
              that are not normally running under SELinux, such as an ext3 formatted disk from  a
              non-SELinux  workstation.   You  can  also  use  context= on filesystems you do not
              trust, such as a floppy.  It also  helps  in  compatibility  with  xattr-supporting
              filesystems  on  earlier 2.4. 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 context="system_u:object_r:remov‐
              able_t".

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

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

              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 quot‐
              ing is required.  For example:

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

              For more details, see selinux(8).

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

              Note  that the real set of all default mount options depends on kernel and filesys‐
              tem type.  See the beginning of this section for more details.

       dev    Interpret character or block special devices on the filesystem.

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

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

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

       dirsync
              All directory updates within the filesystem should  be  done  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).

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

       noiversion
              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

       relatime
              Update inode access times relative to modify or change time.  Access time  is  only
              updated  if  the previous access time was 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 modified.)

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

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

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

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

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

              This mount option significantly reduces writes to the  inode  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 disk.

       nolazytime
              Do not use the lazytime feature.

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

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

       silent Turn on the silent flag.

       loud   Turn off the silent flag.

       owner  Allow  an  ordinary  user  to mount the filesystem if that user is the owner of the
              device.  This option implies the options nosuid and  nodev  (unless  overridden  by
              subsequent options, as in the option line owner,dev,suid).

       remount
              Attempt  to remount an already-mounted filesystem.  This is 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 command.

              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  unspeci‐
              fied source is allowed.

       ro     Mount the filesystem read-only.

       rw     Mount the filesystem read-write.

       sync   All  I/O to the filesystem should be done synchronously.  In the case of media with
              a limited number of write cycles (e.g. some flash drives),  sync  may  cause  life-
              cycle shortening.

       user   Allow  an  ordinary user to mount the filesystem.  The name of the mounting user is
              written to the mtab file (or to the private libmount file in /run/mount on  systems
              without  a  regular  mtab) so that this same user can unmount the filesystem again.
              This option implies the options noexec, nosuid, and  nodev  (unless  overridden  by
              subsequent options, as in the option line user,exec,dev,suid).

       nouser Forbid  an ordinary user to mount the filesystem.  This is the default; it does not
              imply any other options.

       users  Allow any user to mount and to unmount the filesystem, even when some  other  ordi‐
              nary  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 applica‐
              tion-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).

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

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

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

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

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

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

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

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

       protect
              Do not allow any changes to the protection bits on the filesystem.

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

       verbose
              Print an informational message for each successful mount.

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

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

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

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

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

       grpquota|noquota|quota|usrquota
              These  options  are  accepted  but ignored.  (However, quota 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 administration.

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

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

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

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

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

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

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

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

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

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

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

       discard
              Disable/enable the discard mount option.  The discard function issues frequent com‐
              mands  to let the block device reclaim space freed by the filesystem.  This is use‐
              ful 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.)

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

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

       flushoncommit
              The flushoncommit mount option forces any data dirtied by a write in a prior trans‐
              action  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.

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

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

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

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

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

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

       nodatasum
              Enable/disable data checksumming for newly created files.  This option implies dat‐
              acow.

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

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

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

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

       nospace_cache
              Disable freespace cache loading without clearing the cache.

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

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

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

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

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

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

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

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

Mount options for coherent
       None.

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

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

       mode=value
              Sets the mode of the mountpoint.

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

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

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

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

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

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

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

       ptmxmode=value

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

              With the support for multiple instances of devpts (see newinstance  option  above),
              each  instance  has a private ptmx node in the root of the devpts filesystem (typi‐
              cally /dev/pts/ptmx).

              For compatibility with older versions of the kernel, the default mode  of  the  new
              ptmx  node  is 0000.  ptmxmode=value specifies a more useful mode for the ptmx node
              and is highly recommended when the newinstance option is specified.

              This option is only implemented in linux  kernel  versions  starting  with  2.6.29.
              Further,  this  option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled
              in the kernel configuration.

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

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

       bsddf|minixdf
              Set the behavior for the statfs system call.  The minixdf 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 behav‐
              ior 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.

       errors={continue|remount-ro|panic}
              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.

       grpquota|noquota|quota|usrquota
              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.

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

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

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

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

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

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

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

       journal=inum
              When a journal already exists, this option is ignored.  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.

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

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

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

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

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

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

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

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

       barrier=0 / barrier=1
              This  disables / enables the use of write barriers in the jbd code.  barrier=0 dis‐
              ables, barrier=1 enables (default).  This also requires an IO stack which can  sup‐
              port  barriers, and if jbd gets an error on a barrier write, it will disable barri‐
              ers again with a warning.  Write barriers enforce proper on-disk ordering of  jour‐
              nal  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  barri‐
              ers may safely improve performance.

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

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

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

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

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

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

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

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

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

              The ext4 filesystem enables write barriers by default.

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

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

       delalloc
              Deferring block allocation until write-out time.

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

       max_batch_time=usec
              Maximum  amount of time ext4 should wait for additional filesystem operations to be
              batch together with a synchronous write operation.  Since a synchronous write oper‐
              ation  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 algo‐
              rithm used is designed to automatically tune for the speed of the disk, by  measur‐
              ing  the  amount of time (on average) that it takes to finish committing a transac‐
              tion.  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.

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

       journal_ioprio=prio
              The  I/O  priority  (from  0 to 7, where 0 is the highest priority) which should be
              used for I/O operations submitted by kjournald2 during a  commit  operation.   This
              defaults to 3, which is a slightly higher priority than the default I/O priority.

       abort  Simulate  the effects of calling ext4_abort() for debugging purposes.  This is nor‐
              mally used while remounting a filesystem which is already mounted.

       auto_da_alloc|noauto_da_alloc
              Many broken applications don't use fsync() when replacing existing files  via  pat‐
              terns such as

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

              or worse yet

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

              If  auto_da_alloc  is enabled, ext4 will detect the replace-via-rename and replace-
              via-truncate patterns and force that any delayed allocation  blocks  are  allocated
              such  that  at  the next journal commit, in the default data=ordered mode, the data
              blocks of the new file are forced to disk before the rename() operation is  commit‐
              ted.   This  provides  roughly the same level of guarantees as ext3, and avoids the
              "zero-length" problem that can happen when a  system  crashes  before  the  delayed
              allocation blocks are forced to disk.

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

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

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

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

       block_validity/noblock_validity
              This  options  allows  to  enables/disables  the  in-kernel  facility  for tracking
              filesystem metadata blocks within internal data  structures.   This  allows  multi-
              block  allocator  and  other 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.

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

       max_dir_size_kb=n
              This limits the size of the directories so that any attempt to expand  them  beyond
              the  specified  limit  in  kilobytes will cause an ENOSPC error.  This is useful in
              memory-constrained environments, where a very large directory can cause severe per‐
              formance  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  sys‐
              tem's style.)

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

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

       blocksize={512|1024|2048}
              Set blocksize (default 512).  This option is obsolete.

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

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

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

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

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

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

              2      Other users can change timestamp.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       dos1xfloppy
              If set, use a fallback default BIOS Parameter Block  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.

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

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

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

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

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

              nostale_ro:  This option bases the inode number and filehandle on the on-disk loca‐
              tion 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 oper‐
              ations such as rename, create and unlink could cause  filehandles  that  previously
              pointed  at one file to point at a different file, potentially causing data corrup‐
              tion. For this reason, this option also mounts the filesystem readonly.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       session=n
              Select the CDROM session to mount.  Defaults to leaving that decision to the  CDROM
              driver.  This option will fail with 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.)

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

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

       conv={binary|text|auto}
              For conv=text, delete some random CRs (in particular,  all  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
              default.

       nocheck
              Do not abort mounting when certain consistency checks fail.

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

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

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

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

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

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

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

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

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

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

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

       conv={a[uto]|b[inary]|m[text]|t[ext]}
              (Default:  conv=binary.)   Since  Linux  1.3.54  this option has no effect anymore.
              (And non-binary settings used to be very 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.

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

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

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

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

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

Mount options for jfs
       iocharset=name
              Character set to use for converting from Unicode to ASCII.  The default is to do no
              conversion.   Use  iocharset=utf8  for  UTF8  translations.   This  requires   CON‐
              FIG_NLS_UTF8 to be set in the kernel .config file.

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

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

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

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

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

Mount options for minix
       None.

Mount options for msdos
       See mount options for fat.  If the msdos filesystem detects an 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
       iocharset=name
              Character set to use when returning file names.  Unlike VFAT, NTFS suppresses names
              that contain nonconvertible characters.  Deprecated.

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

       utf8   Use UTF-8 for converting file names.

       uni_xlate={0|1|2}
              For 0 (or `no' or `false'), do not use escape sequences for unknown Unicode charac‐
              ters.  For 1 (or `yes' or `true') or 2,  use  vfat-style  4-byte  escape  sequences
              starting with ":".  Here 2 give a little-endian encoding and 1 a byteswapped bigen‐
              dian encoding.

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

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

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

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

Mount options for reiserfs
       Reiserfs is a journaling filesystem.

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

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

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

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

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

       hashed_relocation
              Tunes the block allocator.  This may provide performance improvements in some situ‐
              ations.

       no_unhashed_relocation
              Tunes the block allocator.  This may provide performance improvements in some situ‐
              ations.

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

       nolog  Disable journaling.  This will provide slight performance improvements in some sit‐
              uations  at  the  cost  of losing reiserfs's fast recovery from crashes.  Even with
              this option turned on, reiserfs still performs all 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 pack‐
              ing of files into the tree.

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

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

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

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

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

Mount options for romfs
       None.

Mount options for squashfs
       None.

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

Mount options for sysv
       None.

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

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

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

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

       mode=  Set initial permissions of the root directory.

       uid=   The user id.

       gid=   The group id.

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

              default
                     prefers to allocate memory from the local node

              prefer:Node
                     prefers to allocate memory from the given Node

              bind:NodeList
                     allocates memory only from nodes in NodeList

              interleave
                     prefers to allocate from each node in turn

              interleave:NodeList
                     allocates from each node of NodeList in turn.

              The  NodeList  format  is  a  comma-separated list of decimal numbers and ranges, a
              range being two "hyphen-minus"-separated decimal numbers, the smallest and  largest
              node numbers in the range.  For example, mpol=bind:0–3,5,7,9–15

              Note that trying to mount a tmpfs with an mpol option will fail if the running ker‐
              nel does not support NUMA; and will fail if its nodelist specifies a node which  is
              not  online.   If  your system relies on that tmpfs being mounted, but from time to
              time runs a kernel built without NUMA capability (perhaps a safe recovery  kernel),
              or with fewer nodes online, then it is advisable to omit the mpol option from auto‐
              matic mount options.  It can be added later, when the tmpfs is already  mounted  on
              MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.

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

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

              ubiY   UBI device number 0, volume number Y

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

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

       The following mount options are available:

       bulk_read
              Enable bulk-read.  VFS read-ahead is disabled because it slows down the  file  sys‐
              tem.   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,  One‐
              NAND can do "read-while-load" if it reads more than one NAND page.

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

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

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

       compr={none|lzo|zlib}
              Select the default compressor which is used when new  files  are  written.   It  is
              still possible to read compressed files if mounted with the none option.

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

       undelete
              Show deleted files in lists.

       nostrict
              Unset strict conformance.

       iocharset
              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

       anchor=
              Override standard anchor location.  Default: 256.

       volume=
              Override the VolumeDesc location. (unused)

       partition=
              Override the PartitionDesc location. (unused)

       lastblock=
              Set the last block of the filesystem.

       fileset=
              Override the fileset block location. (unused)

       rootdir=
              Override the root directory location. (unused)

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

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

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

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

              5xbsd  Synonym for ufs2.

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

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

       onerror=value
              Set behavior on error:

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

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

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

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

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

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

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

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

       shortname=mode
              Defines the behavior for creation and display of filenames which fit into 8.3 char‐
              acters.   If a long name for a file exists, it will always be the preferred one for
              display.  There are four modes:

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

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

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

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

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

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

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

Mount options for xenix
       None.

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

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

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

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

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

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

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

              mount /tmp/disk.img /mnt

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

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

       Since Linux 2.6.25 auto-destruction of loop devices is supported, 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.

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

       0      success

       1      incorrect invocation or permissions

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

       4      internal mount bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

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

EXTERNAL HELPERS
       The syntax of external mount helpers is:

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

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

       The command mount does not pass the mount options unbindable, runbindable, private,  rpri‐
       vate,  slave,  rslave, shared, rshared, auto, noauto, comment, x-*, loop, offset and size‐
       limit to the mount. helpers.  All other options are used in a comma-separated list
       as argument to the -o option.

FILES
       /etc/fstab        filesystem table

       /etc/mtab         table of mounted filesystems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try

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

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

       LIBMOUNT_DEBUG=all
              enables libmount debug output

       LIBBLKID_DEBUG=all
              enables libblkid debug output

       LOOPDEV_DEBUG=all
              enables loop device setup debug output

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

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

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

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

       It  is  possible that files /etc/mtab and /proc/mounts don't match on systems with regular
       mtab file. The first file is based only on the mount command options, but the  content  of
       the  second  file  also depends on the kernel and others settings (e.g. remote NFS server.
       In 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 used.

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

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

AUTHORS
       Karel Zak 

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

util-linux                                  July 2014                                    MOUNT(8)

Go-to-top  




Designed by SanjuD(@ngineerbabu)