Provided by: mount_2.32-0.1ubuntu2_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

       The same filesystem may be mounted more than  once,  and  in  some  cases  (e.g.   network
       filesystems)  the  same filesystem maybe be mounted on the same mountpoint more times. The
       mount command does not implement any policy to control  this  behavior.  All  behavior  is
       controlled  by  kernel  and  it is usually specific to filesystem driver. The exception is
       --all, in this case already mounted filesystems are ignored  (see  --all  below  for  more

   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  already  mounted'  from
       mount 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

       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 mount operation
       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.

       It  is  important to understand that "bind" does not to create any second-class or special
       node in the kernel VFS. The "bind" is just another operation to attach a filesystem. There
       is  nowhere  stored information that the filesystem has been attached by "bind" operation.
       The olddir and newdir are independent and the olddir maybe be umounted.

       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 and

       Since util-linux 2.23 the mount command allows to do more propagation  (topology)  changes
       by one mount(8) call and do it 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.  The mount command compares filesystem source, target (and fs
              root  for  bind  mount  or btrfs) to detect already mounted filesystems. The kernel
              table with already mounted filesystems is cached during mount --all. It means  that
              all duplicated fstab entries will be mounted.

              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.


       You  should consult the respective man page for the filesystem first.  If you want to know
       what options the ext4 filesystem supports, then check  the  ext4(5)  man  page.   If  that
       doesn't  exist,  you can also check the corresponding mount page like mount.cifs(8).  Note
       that you might have to install the respective userland tools.

       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 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 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 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 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 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 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  OSTA,  the  Optical  Storage
       Technology  Association, and is often used for DVD-ROM, frequently in the form of a hybrid
       UDF/ISO-9660 filesystem. It is, however, perfectly usable by itself on disk drives,  flash
       drives and other block devices.  See also iso9660.

       uid=   Make  all  files  in  the  filesystem  belong to the given user.  uid=forget can be
              specified independently of (or usually in addition to) uid=<user>  and  results  in
              UDF  not storing uids to the media. In fact the recorded uid is the 32-bit overflow
              uid -1 as defined by the UDF standard.  The value is given as either  <user>  which
              is  a  valid  user name or the corresponding decimal user id, or the special string

       gid=   Make all files in the filesystem belong to the  given  group.   gid=forget  can  be
              specified  independently  of (or usually in addition to) gid=<group> and results in
              UDF not storing gids to the media. In fact the recorded gid is the 32-bit  overflow
              gid  -1 as defined by the UDF standard.  The value is given as either <group> which
              is a valid group name or the corresponding decimal group id, or the special  string

       umask= Mask out the given permissions from all inodes read from the filesystem.  The value
              is given in octal.

       mode=  If mode= is  set  the  permissions  of  all  non-directory  inodes  read  from  the
              filesystem will be set to the given mode. The value is given in octal.

       dmode= If  dmode=  is set the permissions of all directory inodes read from the filesystem
              will be set to the given dmode. The value is given in octal.

       bs=    Set the block size. Default value prior to kernel version 2.6.30  was  2048.  Since
              2.6.30  and  prior  to 4.11 it was logical device block size with fallback to 2048.
              Since 4.11 it is logical block size with fallback to any valid block  size  between
              logical device block size and 4096.

              For  other  details  see  the  updated mkudffs.8 manpage, section COMPATIBILITY and
              BLOCK SIZE.

       unhide Show otherwise hidden files.

              Show deleted files in lists.

              Embed data in the inode. (default)

              Don't embed data in the inode.

              Use short UDF address descriptors.

       longad Use long UDF address descriptors. (default)

              Unset strict conformance.

              Set the NLS character set.

   Mount options for debugging and disaster recovery
       novrs  Ignore the Volume Recognition Sequence and attempt to mount anyway.

              Select the session number for multi-session recorded optical media. (default=  last

              Override standard anchor location. (default= 256)

              Set the last block of the filesystem.

   Unused historical mount options that may be encountered and should be removed
              use uid=<user> instead.

              use gid=<group> instead.

              Override the VolumeDesc location.

              Override the PartitionDesc location.

              Override the fileset block location.

              Override the root directory location.

   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.


       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