Provided by: mount_2.27.1-6ubuntu3.10_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 standard form of the mount command is:

              mount -t type device dir

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

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

              mount /dir

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

              mount --target /mountpoint

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

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

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

                     mount [-l] [-t type]

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

       The device indication.
              Most devices are indicated  by  a  filename  (of  a  block  special  device),  like
              /dev/sda1,  but  there are other possibilities.  For example, in the case of an NFS
              mount, device may look like  It is also possible to  indicate  a
              block  special device using its filesystem label or UUID (see the -L and -U options
              below), or its partition label or UUID.  (Partition identifiers are  supported  for
              example for GUID Partition Tables (GPT).)

              Don't  forget  that  there is no guarantee that UUIDs and labels are really unique,
              especially if you move, share or copy the device.  Use lsblk -o  +UUID,PARTUUID  to
              verify that the UUIDs are really unique in your system.

              The   recommended   setup   is   to   use   tags  (e.g.  LABEL=label)  rather  than
              /dev/disk/by-{label,uuid,partuuid,partlabel} udev symlinks in the /etc/fstab  file.
              Tags  are more readable, robust and portable.  The mount(8) command internally uses
              udev symlinks, so the use of symlinks in /etc/fstab has  no  advantage  over  tags.
              For more details see libblkid(3).

              Note  that mount(8) uses UUIDs as strings.  The UUIDs from the command line or from
              fstab(5)  are  not  converted  to  internal  binary  representation.   The   string
              representation of the UUID should be based on lower case characters.

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

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

                     mount device|dir -o options

              and then the mount options from the command line will be appended to  the  list  of
              options  from /etc/fstab.  The usual behavior is that the last option wins if there
              are conflicting ones.

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

                     mount /dev/foo /dir

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

              Thus, given a line

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

              any  user  can  mount  the  iso9660 filesystem found on an inserted CDROM using the

                     mount /dev/cdrom


                     mount /cd

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

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

                     mount --bind olddir newdir

              or by using this fstab entry:

                     /olddir /newdir none bind

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

                     mount --bind foo foo

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

                     mount --rbind olddir newdir

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

              mount(8) since v2.27 allow to change the options by passing  the  -o  option  along
              with --bind for example:

                     mount --bind,ro foo foo

              This feature is not supported by Linux kernel and it is implemented in userspace by
              additional remount mount(2) syscall. This solution is not atomic.

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

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

              Note  that  read-only  bind will create a read-only mountpoint (VFS entry), but the
              original filesystem superblock will still be writable, meaning that the olddir will
              be writable, but the newdir will be read-only.

              It's impossible to change mount options recursively (for example b  -o rbind,ro).

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

                     mount --move olddir newdir

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

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

              Supported operations are:

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

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

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

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

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

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

              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.

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

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

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

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

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

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

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

       -l, --show-labels
              Add the labels in the mount output.  mount must have permission to  read  the  disk
              device  (e.g.  be  suid root) for this to work.  One can set such a label for ext2,
              ext3 or ext4 using the e2label(8) utility, or for XFS using  xfs_admin(8),  or  for
              reiserfs using reiserfstune(8).

       -M, --move
              Move a subtree to some other place.  See above.

       -n, --no-mtab
              Mount  without writing in /etc/mtab.  This is necessary for example when /etc is on
              a read-only filesystem.

       -O, --test-opts opts
              Limit the set of filesystems to which the -a option applies.  In this regard it  is
              like the -t option except that -O is useless without -a.  For example, the command:

                     mount -a -O no_netdev

              mounts  all filesystems except those which have the option _netdev specified in the
              options field in the /etc/fstab file.

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

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

                     mount -a -t ext2 -O _netdev

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

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

                     mount LABEL=mydisk -o noatime,nodev,nosuid

              For  more  details,  see  the  FILESYSTEM-INDEPENDENT MOUNT OPTIONS and FILESYSTEM-
              SPECIFIC MOUNT OPTIONS sections.

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

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

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

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

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

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

       -T, --fstab path
              Specifies  an alternative fstab file.  If path is a directory then the files in the
              directory are sorted by strverscmp(3); files that start  with  "."  or  without  an
              .fstab  extension  are  ignored.  The option can be specified more than once.  This
              option is  mostly  designed  for  initramfs  or  chroot  scripts  where  additional
              configuration is specified beyond standard system 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.  This is the default.  A synonym is -o rw.

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

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


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

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

              Do not update inode access times on this filesystem (e.g., for faster access on the
              news  spool  to speed up news servers). This works for all inode types (directories
              too), so implies 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.
              Directory inode will not be updated when noatime is set, regardless of this option.

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

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

       exec   Permit execution of binaries.

       noexec Do  not  permit direct execution of any binaries on the mounted filesystem.  (Until
              recently it was possible to run binaries anyway using a  command  like  /lib/ld*.so
              /mnt/binary.  This trick fails since Linux 2.4.25 / 2.6.0.)

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

              Every time the inode is modified, the i_version field will be 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-identifier or set-group-identifier bits to take effect.

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

       silent Turn on the silent flag.

       loud   Turn off the silent flag.

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

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

              The remount functionality follows the standard way the  mount  command  works  with
              options  from fstab.  This means that the mount command only doesn't read fstab (or
              mtab) when both the device and dir are specified.

              mount -o remount,rw /dev/foo /dir

              After this call all old mount options are replaced and arbitrary stuff  from  fstab
              (or  mtab)  is  ignored,  except the loop= option which is internally generated and
              maintained by the mount command.

              mount -o remount,rw  /dir

              After this call mount reads fstab and merges these options with  the  options  from
              the  command  line  (-o).  If  no  mountpoint  found  in  fstab  than  remount with
              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 mtab file, nor
              sent to the mount.type helpers nor to the  mount(2)  system  call.   The  suggested
              format is x-appname.option (e.g. x-systemd.automount).

              Allow  to  make  a  target  directory  (mountpoint).   The  optional  argument mode
              specifies the filesystem access mode used for  mkdir(2)  in  octal  notation.   The
              default mode is 0755.  This functionality is supported only for root users.


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

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

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

              Support POSIX Access Control Lists (or not).

              Set the behavior for the statfs system call.  The minixdf behavior is to return  in
              the  f_blocks  field  the total number of blocks of the filesystem, while the bsddf
              behavior (which is the default) is to subtract the overhead blocks used by the ext2
              filesystem and not available for file storage.  Thus

              % mount /k -o minixdf; df /k; umount /k

              Filesystem  1024-blocks   Used  Available  Capacity  Mounted on
              /dev/sda6     2630655    86954   2412169      3%     /k

              % mount /k -o bsddf; df /k; umount /k

              Filesystem  1024-blocks  Used  Available  Capacity  Mounted on
              /dev/sda6     2543714      13   2412169      0%     /k

              (Note  that this example shows that one can add command-line options to the options
              given in /etc/fstab.)

       check=none or nocheck
              No checking is done at mount time.  This is the default.  This is fast.  It is wise
              to  invoke  e2fsck(8)  every  now  and  then,  e.g.  at boot time.  The non-default
              behavior is unsupported (check=normal and check=strict options have been  removed).
              Note  that  these mount options don't have to be supported if ext4 kernel driver is
              used for ext2 and ext3 filesystems.

       debug  Print debugging info upon each (re)mount.

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

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

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

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

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

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

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

              Support "user." extended attributes (or not).

Mount options for ext3

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Mount options for ext4

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

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

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

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

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

              The ext4 filesystem enables write barriers by default.

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

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

              Deferring block allocation until write-out time.

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

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

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

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

       abort  Simulate  the  effects  of  calling  ext4_abort()  for debugging purposes.  This is
              normally used while remounting a filesystem which is already mounted.

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

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

              or worse yet

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

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

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

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

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

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

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

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

              This limits the size of the directories so that any attempt to expand  them  beyond
              the  specified  limit  in  kilobytes will cause an ENOSPC error.  This is useful in
              memory-constrained environments, where a very  large  directory  can  cause  severe
              performance  problems  or  even  provoke the Out Of Memory killer. (For example, if
              there is only 512 MB memory available, a 176 MB directory may seriously  cramp  the
              system's style.)

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

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 pickiness can be chosen:

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

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

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

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

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

                     No translation is performed.  This is the default.

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

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

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

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

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

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

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

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

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

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

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

              Do not abort mounting when certain consistency checks fail.

Mount options for iso9660

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              Session begins from sector xxx. (Since 2.3.4.)

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

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

Mount options for ramfs

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

Mount options for reiserfs

       Reiserfs is a journaling filesystem.

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

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

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

              ubiY   UBI device number 0, volume number Y

                     UBI device number X, volume with name NAME

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

       The following mount options are available:

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

              Do not bulk-read.  This is the default.

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

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

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

Mount options for udf

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

              Show deleted files in lists.

              Unset strict conformance.

              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

              Override standard anchor location.  Default: 256.

              Override the VolumeDesc location. (unused)

              Override the PartitionDesc location. (unused)

              Set the last block of the filesystem.

              Override the fileset block location. (unused)

              Override the root directory location. (unused)

Mount options for ufs

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

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

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

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

              5xbsd  Synonym for ufs2.

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

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


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

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

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

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

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

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

              mount /tmp/disk.img /mnt

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

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

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

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


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

       0      success

       1      incorrect invocation or permissions

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

       4      internal mount bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

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


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


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

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

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

       It is possible that files /etc/mtab and /proc/mounts don't match on systems  with  regular
       mtab  file.  The first file is based only on the mount command options, but the content of
       the second file also depends on the kernel and others settings (e.g.  remote  NFS  server.
       In  particular case the mount command may reports unreliable information about a NFS mount
       point and the /proc/mounts file usually  contains  more  reliable  information.)  This  is
       another reason to replace mtab file with symlink to the /proc/mounts file.

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