Provided by: mount_2.31.1-0.4ubuntu3_amd64 bug


       mount - mount a filesystem


       mount [-l|-h|-V]

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

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

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


       All  files  accessible  in a Unix system are arranged in one big tree, the file hierarchy,
       rooted at /.  These files can be spread out  over  several  devices.   The  mount  command
       serves  to  attach  the filesystem found on some device to the big file tree.  Conversely,
       the umount(8) command will detach it again.  The filesystem is used to control how data is
       stored on the device or provided in a virtual way by network or another services.

       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 option -t type is optional.  The mount command is usually able  to
       detect a filesystem.  The root permissions are necessary to mount a filesystem by default.
       See section "Non-superuser mounts" below for more details.  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 and filesystem
       Most  devices are indicated by a filename (of a block special device), like /dev/sda1, but
       there are other possibilities.  For example, in the case of an NFS mount, device may  look
       like  It is also possible to indicate a block special device using its
       filesystem label or UUID (see the -L and -U options below),  or  its  partition  label  or
       UUID.  Partition identifiers are supported for example for GUID Partition Tables (GPT).

       The  device  name  of  disk  partitions  are unstable; hardware reconfiguration, adding or
       removing a device can cause change in names. This is reason why it's strongly  recommended
       to use filesystem or partition identificators like UUID or LABEL.

       The  command  lsblk  --fs  provides overview of filesystems, LABELs and UUIDs on available
       block devices.  The command blkid -p <device> provides details about a filesystem  on  the
       specified device.

       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.   UUID=uuid)   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

   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

       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 strongly
       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
       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

       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).

       mount(8)  since  v2.31  ignores the bind flag from /etc/fstab on remount operation (if "-o
       remount" specified on command line). This is necessary to fully control mount  options  on
       remount  by  command  line. In the previous versions the bind flag has been always applied
       and it was impossible to  re-define  mount  options  without  interaction  with  the  bind
       semantic.  This  mount(8)  behavior  does  not  affect  situations  when "remount,bind" is
       specified in the /etc/fstab file.

   The move operation
       Move a mounted tree to another place (atomically).  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


       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

       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

       -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

                     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
              '' 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

              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.


       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

       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.

              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

              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 \

              For more details, see selinux(8).

              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.

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

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

              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.

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

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

              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

              Update inode access times relative to modify or change time.  Access time  is  only
              updated  if  the previous access time was earlier than the current modify or change
              time.  (Similar to noatime, but it doesn't break mutt or  other  applications  that
              need to know if a file has been read since the last time it was 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.

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

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

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

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

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

              The on-disk timestamps are updated only when:

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

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

              - an undeleted inode is evicted from memory

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

              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).

              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 operation together with the bind flag has special semantic. See above,
              the subsection Bind mounts.

              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

       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.

              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.


       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

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

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

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

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

              Print an informational message for each successful mount.

              Prefix used before volume name, when following a link.

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

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

              Give explicitly the location of the root block.

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

              These  options  are  accepted  but ignored.  (However, quota utilities may react to
              such strings in /etc/fstab.)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              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

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

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

              Disable freespace cache loading without clearing the cache.

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

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

              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.

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

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

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

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

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

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

   Mount options for coherent

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

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

              Sets the mode of the mountpoint.

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

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

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

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

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

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

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


              Set the mode for the new ptmx device node in the devpts 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, ext3 and ext4
       See the options section of the ext2(5), ext3(5) or ext4(5) man page (the e2fsprogs package
       must be installed).

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

              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

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

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

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

              This option controls the permission check of mtime/atime.

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

              2      Other users can change timestamp.

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

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

              Three different levels of pickyness can be chosen:

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

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

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

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

              This option is obsolete and may fail or being ignored.

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

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

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

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

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

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

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

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

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

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

              Set  offset for conversion of timestamps from local time used by FAT to UTC.  I.e.,
              minutes 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

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

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

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

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

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

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

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

       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.

              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

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

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

              This option is obsolete and may fail or being ignored.

              Do not abort mounting when certain consistency checks fail.

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

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

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

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

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

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

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

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

              For non-Rock Ridge volumes, give all files the indicated mode.  (Default: read  and
              execute permission for everybody.)  Octal mode values require 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

              Set the block size to the indicated value.  (Default: block=1024.)

              This option is obsolete and may fail or being ignored.

       cruft  If  the  high byte of the file length contains other garbage, set this mount option
              to ignore the high order bits of the file length.  This implies that a file  cannot
              be larger than 16 MB.

              Select number of session on multisession CD.

              Session begins from sector xxx.

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

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

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

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

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

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

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

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

              These options are accepted but ignored.

   Mount options for minix

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

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

   Mount options for nfs and nfs4
       See the options section of the nfs(5) man page (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
              Character set to use when returning file names.  Unlike VFAT, NTFS suppresses names
              that contain nonconvertible characters.  Deprecated.

              New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

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

              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

       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

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

              The upperdir is normally on a writable filesystem.

              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.
       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.

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

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

              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

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

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

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

              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

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

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

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

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

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

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

   Mount options for romfs

   Mount options for squashfs

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

   Mount options for sysv

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

              The same as size, but in blocks of PAGE_CACHE_SIZE

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

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

                     prefers to allocate memory from the local node

                     prefers to allocate memory from the given Node

                     allocates memory only from nodes in NodeList

                     prefers to allocate from each node in turn

                     allocates from each node of NodeList in turn.

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

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

                     UBI device number X, volume with name NAME

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

       The following mount options are available:

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

              Do not bulk-read.  This is the default.

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

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

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

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

              Show deleted files in lists.

              Unset strict conformance.

              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

              Override standard anchor location.  Default: 256.

              Override the VolumeDesc location. (unused)

              Override the PartitionDesc location. (unused)

              Set the last block of the filesystem.

              Override the fileset block location. (unused)

              Override the root directory location. (unused)

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

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

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

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

              5xbsd  Synonym for ufs2.

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

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

              Set behavior on error:

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

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

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

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

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

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

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

              Defines the behavior for creation and display  of  filenames  which  fit  into  8.3
              characters.   If a long name for a file exists, it will always be the preferred one
              for display.  There are four 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

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


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

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

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

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

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

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

              mount /tmp/disk.img /mnt

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

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

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

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

       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.


       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


       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.


       /etc/fstab        filesystem table

       /etc/mtab         table of mounted filesystems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try


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

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

              enables libmount debug output

              enables libblkid debug output

              enables loop device setup debug output


       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)


       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.


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


       Karel Zak <>


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