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       mount [-lhV]

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

       mount [-fnrsvw] [-o option[,option]...]  device|dir

       mount [-fnrsvw] [-t vfstype] [-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  sev-
       eral  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 directory or 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 --target or --source  options
       to avoid ambivalent interpretation of the given argument. For example

              mount --target /mountpoint

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

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

              mount [-l] [-t type]
                     lists all mounted filesystems (of type type).  The option
                     -l adds the labels in this listing.  See below.

       The device indication.
              Most devices are indicated by a file name (of  a  block  special

              Note that mount(8) uses UUIDs as strings. The UUIDs from command
              line  or fstab(5) are not converted to internal binary represen-
              tation. 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 could be overridden by
              --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 simul-

              When  mounting  a filesystem mentioned in fstab or mtab, it suf-
              fices to give only the device, or only the mount point.

              The programs mount and  umount  maintain  a  list  of  currently
              mounted  filesystems in the file /etc/mtab.  If no arguments are
              given to mount, this list is printed.

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

                     mount /dev/foo /dir

              If you want to override mount options from /etc/fstab  you  have
              to use:

                     mount device|dir -o <options>

              and then the mount options from command line will be appended to
              the list of options from /etc/fstab.   The  usual  behaviour  is
              that the last option wins if there is more duplicated options.

              Thus, given a line

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

              any  user  can  mount  the iso9660 filesystem found on his CDROM
              using the command

                     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, 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 shortoption
                     mount -B olddir newdir
              or fstab entry is:
                     /olddir /newdir none bind

              After  this  call the same contents is 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 sub-
              mounts is attached a second place using

                     mount --rbind olddir newdir

              or shortoption

                     mount -R olddir newdir

              Note that the filesystem mount options will remain the  same  as
                     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
              with  -o rbind,ro).

       The move operation.
              Since  Linux  2.5.1  it is possible to atomically move a mounted
              tree to another place. The call is
                     mount --move olddir newdir
              or shortoption
                     mount -M olddir newdir
              This will cause the contents  which  previously  appeared  under
              olddir  to  be  accessed under newdir.  The physical location of
              the files is not changed.  Note that the  olddir  has  to  be  a

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

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

              Supported operations:
                     mount --make-shared mountpoint
                     mount --make-slave mountpoint
                     mount --make-private mountpoint
                     mount --make-unbindable mountpoint

              The following commands allows 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

              (private,  slave, shared, unbindable, rprivate, rslave, rshared,

              For example
                     mount --make-private --make-unbindable /dev/sda1 /A

              is the same as
                     mount /dev/sda1 /A
                     mount --make-private /A
                     mount --make-unbindable /A


       The full set of mount options used by an invocation of mount is  deter-
       mined by first extracting the mount options for the filesystem from the
       fstab table, then applying any options specified by  the  -o  argument,
       and finally applying a -r or -w option, when present.

       Command line options available for the mount command:

       -V, --version
              Output version.

       -h, --help
              Print a help message.

       -v, --verbose
              Verbose mode.

       -a, --all
              Mount all filesystems (of the given types) mentioned in fstab.

       -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 deter-
              mine 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 existing  record  in  /etc/mtab
              and  fails when the record already exists (with regular non-fake
              mount, this check is done by kernel).

       -i, --internal-only
       -c, --no-canonicalize
              Don't canonicalize paths. The mount  command  canonicalizes  all
              paths  (from  command  line  or  fstab) and stores canonicalized
              paths to the /etc/mtab file. This option can  be  used  together
              with the -f flag for already canonicalized absolute paths.

       -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. This option exists for support
              of the Linux autofs-based automounter.

       --source src
              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 argu-
              ment is mount source.

       -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 or ext4 will replay its journal if the filesystem is dirty.
              To prevent this kind of write access, you may want to mount ext3
              or  ext4  filesystem  with  "ro,noload" mount options or set the
              block device to read-only mode, see command blockdev(8).

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

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

       -U, --uuid uuid
              Mount  the  partition  that  has  the specified uuid.  These two
              options require the file /proc/partitions (present  since  Linux
              2.1.116) to exist.

       -T, --fstab path
              Specifies  alternative fstab file. If the path is directory then
              the files in the directory are sorted  by  strverscmp(3),  files
              that  starts  with  "." or without .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 outside  standard  system  configura-

              Note   that  mount(8)  does  not  pass  the  option  --fstab  to
              /sbin/mount.<type> helpers, it means 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
              the real list of all supported filesystems depends on your  ker-

              The  programs mount and umount support filesystem subtypes.  The
              subtype  is  defined  by   '.subtype'   suffix.    For   example
              'fuse.sshfs'.  It's  recommended  to use subtype notation rather
              than  add  any  prefix  to  the  mount   source   (for   example
              'sshfs#example.com' is depreacated).

              For most types all the mount program has to do is issue a simple
              mount(2) system call, and no detailed knowledge of the  filesys-
              tem  type is required.  For a few types however (like nfs, nfs4,
              cifs, smbfs, ncpfs) ad hoc code is  necessary.  The  nfs,  nfs4,
              cifs,  smbfs,  and  ncpfs filesystems have a separate mount pro-
              gram. In order to make it possible to treat all types in a  uni-
              form  way,  mount  will execute the program /sbin/mount.TYPE (if
              that exists) when called with type TYPE.  Since various 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.

              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 *  only,  mount
              will  read  /proc/filesystems  afterwards. All of the filesystem
              types will be mounted with 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.
              The list of filesystem types can be prefixed with no to  specify
              the  filesystem types on which no action should be taken.  (This
              can be meaningful with the -a option.) For example, the command:

                     mount -a -t nomsdos,ext

              mounts all filesystems except those of type msdos and ext.

       --target dir
              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 argu-
              ment is mount target.

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

                     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

       -o, --options opts
              Options are specified with a -o flag followed by a  comma  sepa-
              rated string of options. For example:

                     mount LABEL=mydisk -o noatime,nouser

              For  more  details, see FILESYSTEM INDEPENDENT MOUNT OPTIONS and

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

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

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


       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

       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 effect only for ext2, ext3, ext4, fat, vfat and ufs):

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

       atime  Do not use noatime feature, then the inode access time  is  con-
              trolled  by kernel defaults. See also the description for stric-
              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 or ext4  formatted  disk  from  a
              non-SELinux  workstation.  You can also use context= on filesys-
              tems you do not trust, such as a floppy. It also helps  in  com-
              patibility  with xattr-supporting filesystems on earlier 2.4.<x>
              kernel versions. Even where xattrs are supported, you  can  save
              time not having to label every file by assigning the entire disk
              one security context.

              A commonly used option  for  removable  media  is  context="sys-

              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  them-
              selves.  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 unla-
              beled  files  in  the policy and requires a filesystem that sup-
              ports xattr labeling.

              The rootcontext= option allows you to explicitly label the  root
              inode of a FS being mounted before that FS or inode becomes vis-
              ible 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  con-

              Warning:  the  context value might contain commas, in which case
              the value has to be properly  quoted,  otherwise  mount(8)  will
              interpret the comma as a separator between mount options.  Don't
              forget that the shell strips off quotes and thus double  quoting
              is required.  For example:

                     mount    -t    tmpfs    none   /mnt   -o   'context="sys-


              Update directory inode access times on this filesystem. This  is
              the default.

              Do not update directory inode access times on this filesystem.

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

       exec   Permit execution of binaries.

       noexec Do  not  allow  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 (i.e., non-root) user to mount the  filesystem
              if  one  of  his  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

              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 ear-
              lier than the current modify or change time. (Similar  to  noat-
              ime,  but  doesn't break mutt or other applications that need to
              know if a file has been read since the last time  it  was  modi-

              default system mount options see /proc/mounts.

              Use  the  kernel's  default  behaviour  for  inode  access  time

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

       nosuid Do not allow set-user-identifier or set-group-identifier bits to
              take effect. (This seems safe, but is in fact rather  unsafe  if
              you have suidperl(1) installed.)

       silent Turn on the silent flag.

       loud   Turn off the silent flag.

       owner  Allow  an ordinary (i.e., non-root) user to mount the filesystem
              if he 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  com-
              monly  used  to  change  the mount flags for a filesystem, espe-
              cially to make a  readonly  filesystem  writable.  It  does  not
              change device or mount point.

              The remount functionality follows the standard way how the mount
              command works with options from fstab. It means the  mount  com-
              mand doesn't read fstab (or mtab) only when a device and dir are
              fully specified.

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

              After this call all old mount options are replaced and arbitrary
              stuff  from  fstab  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 (or  mtab)  and  merges  these
              options with options from command line ( -o ).

       ro     Mount the filesystem read-only.

       rw     Mount the filesystem read-write.

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

       x-*    All  options  prefixed  with "x-" are interpreted as comments or
              userspace applications specific options. These options  are  not
              stored  to  mtab  file, send to mount.<type> helpers or mount(2)
              system call. The suggested format is x-<appname>.<option>  (e.g.

              Allow  to  make  a  target  directory (mountpoint). The optional
              argument <mode> specifies the file system 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  Documenta-

Mount options for adfs

       uid=value and gid=value
              Set the owner and group of the files in the filesystem (default:

       ownmask=value and othmask=value
              Set the permission mask for ADFS 'owner' permissions and 'other'
              permissions,  respectively  (default:  0700  and  0077,  respec-
              tively).    See    also    /usr/src/linux/Documentation/filesys-

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 orig-
              inal 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 filesys-

       usemp  Set uid and gid of the root of the filesystem to the uid and gid
              (Default:  2.)  Number  of  unused  blocks  at  the start of the

              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  utili-
              ties may react to such strings in /etc/fstab.)

Mount options for cifs

       See the options section of the mount.cifs(8) man page (cifs-utils pack-
       age must be installed).

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

       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.

              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 filesys-

              With  the  support  for multiple instances of devpts (see newin-
              stance 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  start-
              ing  with  2.6.29.  Further  this  option  is valid only if CON-
              FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel  configu-

Mount options for ext

       None.  Note that the `ext' filesystem is obsolete. Don't use it.  Since
       Linux version 2.1.21 extfs is no longer part of the kernel source.

Mount options for ext2

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

              Support POSIX Access Control Lists (or not).

              Set the behaviour for the statfs system call. The minixdf behav-
              iour  is  to  return  in  the f_blocks field the total number of
              blocks of the filesystem, while the bsddf  behaviour  (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

              Define the behaviour when  an  error  is  encountered.   (Either
              ignore  errors  and  just mark the filesystem erroneous and con-
              tinue, 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  sup-
              port. 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

       resgid=n and resuid=n
              The ext2 filesystem reserves a certain percentage of the  avail-
              able 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

       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  1k
              units.  Thus,  if  you  want  to  use  logical  block 32768 on a
              filesystem with 4k blocks, use "sb=131072".

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

              journal,  overwriting  the  old contents of the file whose inode
              number is inum.

              When the external  journal  device's  major/minor  numbers  have
              changed,  this option allows the user to specify the new journal
              location.  The journal device  is  identified  through  its  new
              major/minor numbers encoded in devnum.

              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 filesys-
              tem, pass the mode to the kernel as boot parameter, e.g.   root-

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

                     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.

       barrier=0 / barrier=1
              This  enables/disables  barriers.   barrier=0  disables it, bar-
              rier=1 enables it.  Write barriers enforce proper on-disk order-
              ing  of  journal commits, making volatile disk write caches safe
              to use, at some performance penalty.  The ext3  filesystem  does
              not  enable write barriers by default.  Be sure to enable barri-
              ers unless your disks are battery-backed  one  way  or  another.
              Otherwise  you risk filesystem corruption in case of power fail-

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

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,  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  com-
       patible with ext3 or ext2.

              Enable  checksumming  of  the  journal  transactions.  This will
              allow the recovery code in e2fsck and the kernel to detect  cor-
              ruption  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 descrip-
              tor  blocks.  If  enabled older kernels cannot mount the device.
              This will enable 'journal_checksum' internally.

       barrier=0 / barrier=1 / barrier / nobarrier
              This enables/disables the use of write barriers in the jbd code.
              barrier=0 disables, barrier=1 enables.  This also requires an IO
              stack which can support barriers, and if jbd gets an error on  a
              barrier write, it will disable again with a warning.  Write bar-
              riers 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.  The
              mount options "barrier" and "nobarrier"  can  also  be  used  to
              enable  or  disable  barriers,  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

              Deferring block allocation until write-out time.
              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 oper-
              ations  will  join the transaction. The commit time is capped by
              the max_batch_time, which defaults to 15000us (15ms). This opti-
              mization can be turned off entirely by setting max_batch_time to

              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 pur-
              poses.  This is normally  used  while  remounting  a  filesystem
              which is already mounted.

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

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

              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.

              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.
              tines  to  quickly  locate  extents  which  might  overlap  with
              filesystem metadata blocks. This option is intended  for  debug-
              ging  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 unini-
              tialized 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).

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

Mount options for fat

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

              Set blocksize (default 512). This option is obsolete.

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

              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.

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

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

                     Like  "normal",  but names may not contain long parts and
                     special characters that are sometimes used on Linux,  but
                     are  not  accepted by MS-DOS are rejected. (+, =, spaces,

              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 (MS-DOS text format to
              UNIX text format) conversion in the kernel. The  following  con-
              version modes are available:

              binary no translation is performed.  This is the default.

              text   CRLF<-->NL translation is performed on all files.

              auto   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,

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

              For filesystems mounted in binary mode, a conversion tool (from-
              dos/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 mod-
              ule loading.  This option is obsolete.

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

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

       nfs    If set, enables in-memory indexing of directory inodes to reduce
              the frequency of ESTALE errors in NFS client operations.  Useful
              only when the filesystem is exported via NFS.

       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.

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

              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 process.)

       dir_umask=n, file_umask=n, umask=n

Mount options for hpfs

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

              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:

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

              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 filesys-
       tem (except that it is read-only, of course).

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

              Disable  the  use of Microsoft Joliet extensions, even if avail-
              able. 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.)
              For non-Rock Ridge volumes, give all files the  indicated  mode.
              (Default:  read  permission  for everybody.)  Since Linux 2.1.37
              one no longer needs to specify the mode in  decimal.  (Octal  is
              indicated by a leading 0.)

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

              Set   the   block   size  to  the  indicated  value.   (Default:

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

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

              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 exten-

              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  key-
              word  with no value will grow the volume to the full size of the
              ignore errors and just mark the filesystem  erroneous  and  con-
              tinue,  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  incon-
       sistency,  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 con-
       structed 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.

              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
              These options are recognized, but have no effect as far as I can

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

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 pre-
                     serves locality,  mapping  lexicographically  close  file
                     names  to  close  hash values.  This option should not be
                     used, as it causes a high probability of hash collisions.

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

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

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

              Tunes the block allocator. This may provide performance improve-
              ments in some situations.

              Tunes the block allocator. This may provide performance improve-
              ments in some situations.

              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 par-
              titions.  Instructs reiserfs to assume that the device has  num-
              ber  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 enables/disables the use of write barriers in the  journal-
              ing  code.   barrier=none disables it, barrier=flush enables it.
              Write barriers enforce proper on-disk ordering of  journal  com-
              mits,  making  volatile  disk  write caches safe to use, at some
              performance penalty. The reiserfs  filesystem  does  not  enable
              write  barriers  by  default.  Be sure to enable barriers unless
              your disks are battery-backed one way or another. Otherwise  you
              risk filesystem corruption in case of power failure.

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  con-
       structed  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

       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, mega and giga)
       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-separated decimal numbers,
              the smallest and largest node numbers in the range.   For  exam-
              ple, 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 sys-
              tem 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  advis-
              able  to  omit the mpol option from automatic mount options.  It
              can be added later, when the tmpfs is already mounted on  Mount-
              Point, 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.

              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.

              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  (Net-

              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

              Set behaviour on error:

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

                     These mount options don't do anything at present; when an

              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 illegal on the vfat filesystem.  The
              escape  sequence  that gets used, where u is the unicode charac-
              ter, 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  behaviour  for  creation  and display of filenames
              which fit into 8.3 characters. If a long name for a file exists,
              it will always be preferred 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  shortname 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

              The default behaviour is for dynamic  end-of-file  preallocation
              size,  which uses a set of heuristics to optimise the prealloca-
              tion size based on the current allocation  patterns  within  the
              file  and  the  access  patterns to the file. Specifying a fixed
              allocsize value turns off the dynamic behaviour.

              The options enable/disable an "opportunistic" improvement to  be
              made  in  the way inline extended attributes are stored on-disk.
              When the new form is used for  the  first  time  when  attr2  is
              selected  (either  when setting or removing extended attributes)
              the on-disk superblock feature bit  field  will  be  updated  to
              reflect this format being in use.

              The  default  behaviour is determined by the on-disk feature bit
              indicating that attr2  behaviour  is  active.  If  either  mount
              option  it  set,  then  that becomes the new default used by the

              CRC enabled filesystems always use the attr2 format, and so will
              reject the noattr2 mount option if it is set.

              Enables/disables  the  use  of  block  layer  write barriers for
              writes into the journal and for data integrity operations.  This
              allows  for drive level write caching to be enabled, for devices
              that support write barriers.

              Enable/disable the issuing of 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 performance impact.

              Note: It is currently recommended that you use the fstrim appli-
              cation to discard unused blocks rather than  the  discard  mount
              option  because  the  performance impact of this option is quite

              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 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.

              Make  the  data  allocator  use  the filestreams allocation mode
              across the entire filesystem rather  than  just  on  directories
              configured to use it.

              inode32  is provided for backwards compatibility with older sys-
              tems and applications, since 64 bits inode numbers  might  cause
              problems  for  some  applications that cannot handle large inode
              numbers.  If applications are in use which do not  handle  inode
              numbers bigger than 32 bits, the inode32 option should be speci-

              If "nolargeio" is specified, the optimal I/O reported in st_blk-
              size  by  stat(2)  will  be  as  small as possible to allow user
              applications to avoid inefficient read/modify/write  I/O.   This
              is typically the page size of the machine, as this is the granu-
              larity of the page cache.

              If "largeio" specified, a filesystem that  was  created  with  a
              "swidth"  specified will return the "swidth" value (in bytes) in
              st_blksize. If the filesystem does not have a "swidth" specified
              but does specify an "allocsize" then "allocsize" (in bytes) will
              be returned instead. Otherwise the behaviour is the same  as  if
              "nolargeio" was specified.

              Set  the  number  of in-memory log buffers.  Valid numbers range
              from 2-8 inclusive.

              The default value is 8 buffers.

              If the memory cost of 8 log buffers is too high  on  small  sys-
              tems,  then  it  may  be  reduced at some cost to performance on
              metadata intensive workloads. The logbsize option below controls
              the size of each buffer and so is also relevent to this case.

              Set  the  size  of  each  in-memory log buffer.  The size may be
              specified in bytes, or in kilobytes with a  "k"  suffix.   Valid
              sizes for version 1 and version 2 logs are 16384 (16k) and 32768
              (32k).  Valid sizes for version 2 logs also include 65536 (64k),
              131072 (128k) and 262144 (256k). The logbsize must be an integer
              multiple of the log stripe unit configured at mkfs time.

              The default value for version 1 logs is 32768, while the default
              value for version 2 logs is MAX(32768, log_sunit).

              Use  an external log (metadata journal) and/or real-time device.
              An XFS filesystem has up to three parts: a data section,  a  log
              section,  and  a  real-time  section.   The real-time section is
              optional, and the log section can be separate from the data sec-
              tion or contained within it.

              often used in combination with "norecovery" for  mounting  read-
              only snapshots.

              Forcibly  turns  off all quota accounting and enforcement within
              the filesystem.

              User disk quota  accounting  enabled,  and  limits  (optionally)
              enforced.  Refer to xfs_quota(8) for further details.

              Group  disk  quota  accounting  enabled  and limits (optionally)
              enforced.  Refer to xfs_quota(8) for further details.

              Project disk quota accounting enabled  and  limits  (optionally)
              enforced.  Refer to xfs_quota(8) for further details.

       sunit=value and swidth=value
              Used to specify the stripe unit and width for a RAID device or a
              stripe volume.  "value" must  be  specified  in  512-byte  block
              units.  These options are only relevant to filesystems that were
              created with non-zero data alignment parameters.

              The sunit and swidth parameters  specified  must  be  compatible
              with the existing filesystem alignment characteristics.  In gen-
              eral, that means the only valid changes to sunit are  increasing
              it by a power-of-2 multiple. Valid swidth values are any integer
              multiple of a valid sunit value.

              Typically the only time these mount  options  are  necessary  if
              after  an underlying RAID device has had it's geometry modified,
              such as adding a new disk to a RAID5 lun and reshaping it.

              Data allocations will be rounded up to stripe  width  boundaries
              when the current end of file is being extended and the file size
              is larger than the stripe width size.

       wsync  When specified, all filesystem namespace operations are executed
              synchronously.  This  ensures  that when the namespace operation
              (create, unlink, etc) completes, the change to the namespace  is
              on  stable  storage.  This is useful in HA setups where failover
              must not result in clients seeing inconsistent namespace presen-
              tation during or after a failover event.

Mount options for xiafs

       None. Although nothing is wrong with xiafs, it is not used much, and is
       not maintained. Probably one shouldn't use  it.   Since  Linux  version
       2.1.21 xiafs is no longer part of the kernel source.

              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 ext4 /tmp/disk.img /mnt

       This  type  of  mount knows about four 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  is supported auto-destruction of loop devices and
       then any loop device allocated by mount will be freed by  umount  inde-
       pendently on /etc/mtab.

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


       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 success), 32  (all  failed)  or  64
       (some failed, some success).


       The syntax of external mount helpers is:

              /sbin/mount.<suffix> spec dir [-sfnv] [-o options] [-t type.sub-

       /etc/filesystems  a list of filesystem types to try


              overrides the default location of the fstab file

              overrides the default location of the mtab file

              enables 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,  ext4, 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.  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.)

       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

       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 <kzak@redhat.com>

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