Provided by: mount_2.30.1-0ubuntu4_amd64 bug

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
       invisible, and as long as this filesystem remains mounted, the pathname dir refers to  the
       root of the filesystem on device.

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

              mount /dir

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

              mount --target /mountpoint

   Listing the mounts
       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.

   Indicating the device
       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 representation
       of the UUID should be based on lower case characters.

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

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

       The command

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

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

   Non-superuser mounts
       Normally, only the superuser can mount filesystems.  However, when fstab contains the user
       option on a line, anybody can mount the corresponding filesystem.

       Thus, given a line

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

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

       Note  that  mount  is  very strict about non-root users and all paths specified on command
       line are verified before fstab is parsed or a helper program  is  executed.  It's  strogly
       recommended to use a valid mountpoint to specify filesystem, otherwise mount may fail. For
       example it's bad idea to use NFS or CIFS source on command line.

       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.

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

              mount --bind olddir newdir

       or by using this fstab entry:

              /olddir /newdir none bind

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

              mount --bind foo foo

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

              mount --rbind olddir newdir

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

       mount(8) since v2.27 allows to change the mount options by passing  the  relevant  options
       along with --bind.  For example:

              mount -o bind,ro foo foo

       This  feature  is  not supported by the Linux kernel; it is implemented in userspace by an
       additional mount(2) remounting system call.  This solution is not atomic.

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

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

       Note  that  a  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  also  possible to change nosuid, nodev, noexec, noatime, nodiratime and relatime VFS
       entry  flags  by  "remount,bind"  operation.  It's  impossible  to  change  mount  options
       recursively (for example with -o rbind,ro).

   The move operation
       Since  Linux 2.5.1 it is possible to atomically move a mounted tree to another place.  The
       call is:

              mount --move olddir newdir

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

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

   Shared subtree operations
       Since  Linux  2.6.15  it is possible to mark a mount and its submounts as shared, private,
       slave or unbindable.  A shared mount provides the ability to create mirrors of that  mount
       such  that mounts and unmounts within any of the mirrors propagate to the other mirror.  A
       slave mount receives propagation from its master, but not vice  versa.   A  private  mount
       carries  no propagation abilities.  An unbindable mount is a private mount which cannot be
       cloned  through  a  bind  operation.    The   detailed   semantics   are   documented   in
       Documentation/filesystems/sharedsubtree.txt file in the kernel source tree.

       Supported operations are:

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

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

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

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

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

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

       For example:

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

       is the same as:

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

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
       section EXTERNAL HELPERS.

       Command-line options available for the mount command are:

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

              Note that it is a bad practice to use mount -a for fstab checking. The  recommended
              solution is findmnt --verify.

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

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

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

       -F, --fork
              (Used in conjunction with -a.)  Fork off  a  new  incarnation  of  mount  for  each
              device.   This  will do the mounts on different devices or different NFS servers in
              parallel.  This has the advantage that it  is  faster;  also  NFS  timeouts  go  in
              parallel.   A  disadvantage  is that the mounts are done in undefined order.  Thus,
              you cannot use this option if you want to mount both /usr and /usr/spool.

       -f, --fake
              Causes everything to be done except  for  the  actual  system  call;  if  it's  not
              obvious,  this  ``fakes''  mounting  the  filesystem.   This  option  is  useful in
              conjunction with the -v flag to determine what the mount command is trying  to  do.
              It  can  also be used to add entries for devices that were mounted earlier with the
              -n option.  The -f option checks for an existing record in /etc/mtab and fails when
              the record already exists (with a regular non-fake mount, this check is done by the
              kernel).

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

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

       -l, --show-labels
              Add the labels in the mount output.  mount must have permission to  read  the  disk
              device  (e.g.  be set-user-ID 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, the subsection The move operation.

       -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-
              SPECIFIC MOUNT OPTIONS sections.

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

       -r, --read-only
              Mount the filesystem read-only.  A synonym is -o ro.

              Note  that, depending on the filesystem type, state and kernel behavior, the system
              may still write to the device.  For example, ext3 and ext4 will replay the  journal
              if  the filesystem is dirty.  To prevent this kind of write access, you may want to
              mount an ext3 or ext4 filesystem with the ro,noload mount options or set the  block
              device itself to read-only mode, see the blockdev(8) command.

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

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

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

       -T, --fstab path
              Specifies  an alternative fstab file.  If path is a directory then the files in the
              directory are sorted by strverscmp(3); files that start  with  "."  or  without  an
              .fstab  extension  are  ignored.  The option can be specified more than once.  This
              option is  mostly  designed  for  initramfs  or  chroot  scripts  where  additional
              configuration is specified beyond standard system 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
              subtype notation rather than add any  prefix  to  the  mount  source  (for  example
              'sshfs#example.com' is deprecated).

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

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

              More than one type may be specified in a comma-separated list,  for  option  -t  as
              well  as in an /etc/fstab entry.  The list of filesystem types for option -t can be
              prefixed with no to 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
              execute the program /sbin/mount.type (if that exists) when called with  type  type.
              Since   different   versions   of  the  smbmount  program  have  different  calling
              conventions, /sbin/mount.smbfs may have to be a  shell  script  that  sets  up  the
              desired call.

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

       -v, --verbose
              Verbose mode.

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

              Note that specify -w on command line forces mount command to  never  try  read-only
              mount  on  write-protected  devices.  The  default is try read-only if the previous
              mount syscall with read-write flags failed.

       -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 relatime and strictatime 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 it 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.<x> kernel versions.  Even where xattrs are supported,
              you can save time not having to label every file by assigning the entire  disk  one
              security context.

              A       commonly       used       option      for      removable      media      is
              context="system_u:object_r:removable_t".

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

              The fscontext= option works for all filesystems, 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
              quoting is required.  For example:

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

              For more details, see selinux(8).

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

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

       dev    Interpret character or block special devices on the filesystem.

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

       diratime
              Update directory inode access times on  this  filesystem.   This  is  the  default.
              (This option is ignored when noatime is set.)

       nodiratime
              Do  not  update  directory  inode access times on this filesystem.  (This option is
              implied when noatime is set.)

       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-ID or set-group-ID bits to take effect.

       nosuid Do not allow set-user-ID or set-group-ID 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 mount does not read fstab (or mtab) only  when
              both 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 is found in fstab,  then  a  remount  with
              unspecified source is allowed.

       ro     Mount the filesystem read-only.

       rw     Mount the filesystem read-write.

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

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

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

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

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

       x-*    The same as X-* options, but stored permanently in the user  space.  It  means  the
              options  are  also  available for umount or another operations.  Note that maintain
              mount options in user space is tricky, because it's necessary  use  libmount  based
              tools  and  there  is  no  guarantee that the options will be always available (for
              example after a move mount operation or in unshared namespace).

              Note that before util-linux v2.30 the x-*  options  have  not  been  maintained  by
              libmount and stored in user space (functionality was the same as have X-* now), but
              due to growing number of use-cases (in initrd, systemd etc.) the functionality have
              been extended to keep existing fstab configurations usable without a change.

       X-mount.mkdir[=mode]
              Allow  to  make  a  target  directory  (mountpoint).   The  optional  argument mode
              specifies the filesystem access mode used for  mkdir(2)  in  octal  notation.   The
              default  mode  is  0755.  This functionality is supported only for root users.  The
              option is  also  supported  as  x-mount.mkdir,  this  notation  is  deprecated  for
              mount.mkdir since v2.30.

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/Documentation/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
              specified multiple times for multiple devices.

       discard
              Disable/enable  the  discard  mount  option.   The discard function issues frequent
              commands to let the block device reclaim space freed by the  filesystem.   This  is
              useful for SSD devices, thinly provisioned LUNs and virtual machine images, but may
              have a 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
              transaction to commit as part of the current  commit.   This  makes  the  committed
              state  a fully consistent view of the filesystem from the application's perspective
              (i.e., it includes all completed filesystem operations).  This was  previously  the
              behavior only when a snapshot is created.

       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)
              manual page for more information about ACLs.

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

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

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

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

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

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

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

       nospace_cache
              Disable freespace cache loading without clearing the cache.

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

       ssd|nossd|ssd_spread
              Options to control ssd allocation  schemes.   By  default,  BTRFS  will  enable  or
              disable  ssd  allocation  heuristics  depending  on  whether  a  rotational or non-
              rotational  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
              number of CPUs + 2, or 8, whichever is smaller.

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

   Mount options for cifs
       See  the  options  section  of  the  mount.cifs(8)  man  page  (cifs-utils 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/<number>.

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

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

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

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

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

              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
              (typically /dev/pts/ptmx).

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

              This option is only implemented in linux  kernel  versions  starting  with  2.6.29.
              Further,  this  option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled
              in the kernel 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
              behavior is unsupported (check=normal and check=strict options have been  removed).
              Note  that  these mount options don't have to be supported if ext4 kernel driver is
              used for ext2 and ext3 filesystems.

       debug  Print debugging info upon each (re)mount.

       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
              set-group-ID bit set, in which case it takes the GID from the parent directory, and
              also gets the set-group-ID 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
              specified group.)

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

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

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

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

       journal=inum
              When a journal already exists, this option is ignored.  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
              identified  either  through its new major/minor numbers encoded in devnum, or via a
              path to the device.

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

       data={journal|ordered|writeback}
              Specifies the journaling mode for file data.  Metadata is always journaled.  To use
              modes  other  than  ordered  on the root 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
                     filesystem  after  its  metadata has been committed to the journal.  This is
                     rumoured to  be  the  highest-throughput  option.   It  guarantees  internal
                     filesystem integrity, however it can allow old data to appear in files after
                     a crash and journal recovery.

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

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

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

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

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

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

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

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

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

       journal_checksum
              Enable checksumming of the journal transactions.  This will allow the recovery code
              in e2fsck and the kernel to detect 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_checksum' internally.

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

              The ext4 filesystem enables write barriers by default.

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

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

       delalloc
              Deferring block allocation until write-out time.

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

       max_batch_time=usec
              Maximum  amount of time ext4 should wait for additional filesystem operations to be
              batch together with a synchronous  write  operation.   Since  a  synchronous  write
              operation  is  going  to  force  a  commit and then a wait for the I/O complete, it
              doesn't cost much, and can be a huge throughput win, we wait for a small amount  of
              time  to see if any other transactions can piggyback on the synchronous write.  The
              algorithm used is designed to automatically tune for the  speed  of  the  disk,  by
              measuring  the  amount  of  time  (on average) that it takes to finish committing a
              transaction.  Call this time the "commit time".  If the time that  the  transaction
              has  been  running  is  less  than  the commit time, ext4 will try sleeping for the
              commit time to see if other operations will join the transaction.  The commit  time
              is  capped  by  the  max_batch_time,  which  defaults  to  15000 µs  (15 ms).  This
              optimization can be turned off entirely by setting max_batch_time to 0.

       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
              normally used while remounting a filesystem which is already mounted.

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

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

              or worse yet

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

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

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

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

       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
              performance  problems  or  even  provoke the Out Of Memory killer. (For example, if
              there is only 512 MB memory available, a 176 MB directory may seriously  cramp  the
              system's style.)

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

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

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

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

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

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

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

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

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

              2      Other users can change timestamp.

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

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

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

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

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

              s[trict]
                     Like "normal", but names 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
              filesystems.  By default, codepage 437 is used.

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

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

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

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

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

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

       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
              inconsistent).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       session=n
              Select the CDROM session to mount.  Defaults to leaving that decision to the  CDROM
              driver.  This option will fail with 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
              overriding  the  information  found  in  the  Rock  Ridge  extensions.    (Default:
              uid=0,gid=0.)

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

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

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

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

       conv={a[uto]|b[inary]|m[text]|t[ext]}
              (Default: conv=binary.)  Since Linux 1.3.54 this  option  has  no  effect  anymore.
              (And non-binary settings used to be very 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
              characters.  The default is iso8859-1.

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

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

       resize=value
              Resize the volume to value  blocks.   JFS  only  supports  growing  a  volume,  not
              shrinking  it.   This  option  is  only  valid during a remount, when the volume is
              mounted read-write.  The resize 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 (the nfs-utils package must be installed).

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

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

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

       utf8   Use UTF-8 for converting file names.

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

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

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

   Mount options for overlay
       Since Linux 3.18 the  overlay  pseudo  filesystem  implements  a  union  mount  for  other
       filesystems.

       An  overlay  filesystem  combines  two  filesystems  -  an  upper  filesystem  and a lower
       filesystem.  When a name exists in both filesystems, the object in the upper filesystem is
       visible  while  the  object  in  the  lower filesystem is either hidden or, in the case of
       directories, merged with the upper object.

       The lower filesystem can be any filesystem supported by Linux and  does  not  need  to  be
       writable.   The lower filesystem can even be another overlayfs.  The upper filesystem will
       normally be writable and if it is it must  support  the  creation  of  trusted.*  extended
       attributes, and must provide a valid d_type in readdir responses, so NFS is not suitable.

       A read-only overlay of two read-only filesystems may use any filesystem type.  The options
       lowerdir and upperdir are combined into a merged directory by using:

              mount -t overlay  overlay  \
                -olowerdir=/lower,upperdir=/upper,workdir=/work  /merged

       lowerdir=directory
              Any filesystem, does not need to be on a writable filesystem.

       upperdir=directory
              The upperdir is normally on a writable filesystem.

       workdir=directory
              The workdir needs to be an empty directory on the same filesystem as upperdir.

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

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

   Mount options for reiserfs
       Reiserfs is a journaling filesystem.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              ubiY   UBI device number 0, volume number Y

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

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

       The following mount options are available:

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

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

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

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

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

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

       undelete
              Show deleted files in lists.

       nostrict
              Unset strict conformance.

       iocharset
              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

       anchor=
              Override standard anchor location.  Default: 256.

       volume=
              Override the VolumeDesc location. (unused)

       partition=
              Override the PartitionDesc location. (unused)

       lastblock=
              Set the last block of the filesystem.

       fileset=
              Override the fileset block location. (unused)

       rootdir=
              Override the root directory location. (unused)

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

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

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

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

              5xbsd  Synonym for ufs2.

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

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

       onerror=value
              Set behavior on error:

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

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

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

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

       uni_xlate
              Translate unhandled Unicode characters to special escaped sequences.  This lets you
              backup and restore filenames that are created with any Unicode characters.  Without
              this option, a '?' is used when no translation is possible.  The  escape  character
              is ':' because it is otherwise invalid on the vfat filesystem.  The escape sequence
              that gets used, where u is the Unicode 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
              characters.  If a long name for a file exists, it will always be the preferred  one
              for display.  There are four modes:

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

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

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

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

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

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

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

   Mount options for xenix
       None.

   Mount options for xfs
       See the options section of the xfs(5) man page (the 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.

       Since util-linux v2.29 mount command re-uses the loop device rather than initialize a  new
       device  if the same backing file is already used for some loop device with the same offset
       and sizelimit. This is necessary to avoid a filesystem corruption.

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,
       rprivate, slave, rslave, shared, rshared, auto, noauto, comment,  x-*,  loop,  offset  and
       sizelimit  to the mount.<suffix> helpers.  All other options are used in a comma-separated
       list as argument to the -o option.

FILES

       /etc/fstab        filesystem table

       /etc/mtab         table of mounted filesystems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try

ENVIRONMENT

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

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

       LIBMOUNT_DEBUG=all
              enables libmount debug output

       LIBBLKID_DEBUG=all
              enables libblkid debug output

       LOOPDEV_DEBUG=all
              enables loop device setup debug output

SEE ALSO

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

BUGS

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

       Some  Linux filesystems don't support -o sync nor -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 the files /etc/mtab and /proc/mounts don't match  on  systems  with  a
       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.  on  a
       remote  NFS server -- in certain cases the mount command may report unreliable information
       about an NFS mount  point  and  the  /proc/mounts  file  usually  contains  more  reliable
       information.)   This  is  another  reason  to  replace the mtab file with a symlink to the
       /proc/mounts file.

       Checking files on NFS filesystems referenced by file descriptors (i.e. the fcntl and ioctl
       families  of  functions) may lead to inconsistent results due to the lack of a consistency
       check in the kernel even if noac is used.

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

HISTORY

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

AUTHORS

       Karel Zak <kzak@redhat.com>

AVAILABILITY

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