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       mount - mount a file system


       mount [-lhV]

       mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
       mount [-fnrsvw] [-o options [,...]] 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
       several  devices.  The  mount  command serves to attach the file system
       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 file system 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 file
       system remains mounted, the pathname dir refers to the root of the file
       system on device.

       Three forms of invocation do not actually mount anything:
              mount -h
       prints a help message;
              mount -V
       prints a version string; and just
              mount [-l] [-t type]
       lists  all mounted file systems (of type type).  The option -l adds the
       (ext2, ext3 and XFS) labels in this listing.  See below.

       Since Linux 2.4.0 it is possible to remount part of the file  hierarchy
       somewhere else. The call is
              mount --bind olddir newdir
       After this call the same contents is accessible in two places.  One can
       also remount a single file (on a single file).

       This call attaches only (part of) a  single  filesystem,  not  possible
       submounts.  The entire file hierarchy including submounts is attached a
       second place using
              mount --rbind olddir newdir

       Note that the filesystem mount options will remain the same as those on
       the  original  mount  point,  and  cannot  be changed by passing the -o
       option along with --bind/--rbind.

       Since Linux 2.5.1 it is possible to atomically move a mounted  tree  to
       another place. The call is
              mount --move olddir newdir

       The  proc file system 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.)

       Most devices are indicated by a file name (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
       possible  to  indicate a block special device using its volume label or
       UUID (see the -L and -U options below).

       The file /etc/fstab (see fstab(5)), may contain lines  describing  what
       devices  are  usually  mounted where, using which options. This file is
       used in three ways:

       (i) The command
              mount -a [-t type] [-O optlist]
       (usually given in a bootscript) causes all file  systems  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.

       (ii) When mounting a file system mentioned in  fstab,  it  suffices  to
       give only the device, or only the mount point.

       (iii)  Normally,  only  the superuser can mount file systems.  However,
       when fstab contains the user option on a line, anybody  can  mount  the
       corresponding system.

       Thus, given a line
              /dev/cdrom  /cd  iso9660  ro,user,noauto,unhide
       any user can mount the iso9660 file system found on his 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, 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 programs mount and umount maintain a list of currently mounted file
       systems in the file /etc/mtab.  If no arguments  are  given  to  mount,
       this list is printed.

       When the proc filesystem is mounted (say at /proc), the files /etc/mtab
       and /proc/mounts have very similar contents. The  former  has  somewhat
       more   information,  such  as  the  mount  options  used,  but  is  not
       necessarily up-to-date (cf. the -n option below).  It  is  possible  to
       replace  /etc/mtab  by  a symbolic link to /proc/mounts, and especially
       when you have very large numbers of mounts things will be  much  faster
       with  that  symlink,  but  some  information  is  lost that way, and in
       particular working with the loop device will be  less  convenient,  and
       using the "user" option will fail.


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

       Options available for the mount command:

       -V     Output version.

       -h     Print a help message.

       -v     Verbose mode.

       -p passwdfd
              If the mount requires a passphrase to be entered, read  it  from
              file  descriptor passwdfd instead of from the terminal. If mount
              uses encrypted loop device and gpgkey= mount option is not being
              used (no gpg key file), then mount attempts to read 65 keys from
              passwdfd, each key at  least  20  characters  and  separated  by
              newline.  If  mount  successfully reads 64 or 65 keys, then loop
              device is put to multi-key mode. If mount encounters end-of-file
              before  64 keys are read, then only first key is used in single-
              key mode.

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

       -F     (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     Causes everything to be done except for the actual system  call;
              if  it’s  not  obvious, this ‘‘fakes’’ mounting the file system.
              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.

       -i     Don’t  call  the  /sbin/mount.<filesystem>  helper  even  if  it

       -l     Add the ext2, ext3 and XFS 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  or  ext3
              using  the e2label(8) utility, or for XFS using xfs_admin(8), or
              for reiserfs using reiserfstune(8).

       -n     Mount without writing  in  /etc/mtab.   This  is  necessary  for
              example when /etc is on a read-only file system.

       -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.

       -r     Mount the file system read-only. A synonym is -o ro.

       -w     Mount the file system read/write. This is the default. A synonym
              is -o rw.

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

       -U 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 vfstype
              The  argument  following  the  -t  is  used to indicate the file
              system  type.   The  file  system  types  which  are   currently
              supported  include:  adfs, affs, autofs, coda, coherent, cramfs,
              devpts, efs, ext, ext2, ext3, hfs, hpfs,  iso9660,  jfs,  minix,
              msdos,  ncpfs,  nfs,  ntfs,  proc, qnx4, ramfs, reiserfs, romfs,
              smbfs, sysv, tmpfs, udf, ufs, umsdos, usbfs, vfat,  xenix,  xfs,
              xiafs.   Note  that  coherent, sysv and xenix are equivalent and
              that xenix and coherent will be removed at  some  point  in  the
              future — use sysv instead. Since kernel version 2.1.21 the types
              ext and xiafs do not exist anymore. Earlier, usbfs was known  as

              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,
              smbfs, ncpfs) ad hoc code is necessary. The nfs ad hoc  code  is
              built  in, but smbfs and ncpfs 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  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.  If mount was compiled
              with  the  blkid  library, the guessing is done by this library.
              Otherwise, mount guesses itself by probing  the  superblock;  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

              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.  Warning:  the  probing  uses  a
              heuristic  (the  presence  of  appropriate  ‘magic’),  and could
              recognize the wrong filesystem type, possibly with  catastrophic
              consequences.  If  your  data  is  valuable,  don’t ask mount to

              More than one type may be specified in a comma  separated  list.
              The list of file system types can be prefixed with no to specify
              the file system 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 file systems except those of type msdos and ext.

       -O     Used  in conjunction with -a, to limit the set of filesystems to
              which the -a is applied.  Like -t in this regard except that  it
              is  useless  except  in  the  context  of  -a.  For example, the
                     mount -a -O no_netdev
              mounts all file systems  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

              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 are specified  with  a  -o  flag  followed  by  a  comma
              separated  string  of  options.   Some of these options are only
              useful when they appear in the /etc/fstab file.   The  following
              options  apply to any file system that is being mounted (but not
              every file system actually honors them - e.g., the  sync  option
              today has effect only for ext2, ext3 and ufs):

              async  All I/O to the file system should be done asynchronously.

              atime  Update inode access time for each  access.  This  is  the

              auto   Can be mounted with the -a option.

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

              dev    Interpret character or block special devices on the  file

              exec   Permit execution of binaries.

              group  Allow an ordinary (i.e., non-root) user to mount the file
                     system 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).

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

                     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).

                     Do not update inode access  times  on  this  file  system
                     (e.g,  for  faster  access  on the news spool to speed up
                     news servers).

              noauto Can only be mounted explicitly (i.e., the -a option  will
                     not cause the file system to be mounted).

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

              noexec Do not allow direct execution  of  any  binaries  on  the
                     mounted  file system.  (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  /

              nomand Do not allow mandatory locks on this filesystem.

              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.)

              nouser Forbid an ordinary (i.e., non-root)  user  to  mount  the
                     file system.  This is the default.

              owner  Allow an ordinary (i.e., non-root) user to mount the file
                     system 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

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

              ro     Mount the file system read-only.

              rw     Mount the file system read-write.

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

              sync   All  I/O to the file system should be done synchronously.

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

              user   Allow  an  ordinary  user  to mount the file system.  The
                     name of the mounting user is written to mtab so  that  he
                     can  unmount  the file system again.  This option implies
                     the options noexec, nosuid, and nodev (unless  overridden
                     by   subsequent   options,   as   in   the   option  line

              users  Allow every user to mount and unmount  the  file  system.
                     This option implies the options noexec, nosuid, and nodev
                     (unless overridden  by  subsequent  options,  as  in  the
                     option line users,exec,dev,suid).

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

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


       The following options apply only to certain file systems.  We sort them
       by file system. 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

Mount options for adfs

       uid=value and gid=value
              Set  the  owner  and  group  of  the  files  in  the file system
              (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 file system (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 file

       usemp  Set uid and gid of the root of the file system 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

              Give explicitly the location of the root block.

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

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

Mount options for coherent


Mount options for devpts

       The  devpts  file system is a pseudo file system, 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.

Mount options for ext

       None.   Note  that  the  ‘ext’  file  system is obsolete. Don’t use it.
       Since Linux version 2.1.21 extfs  is  no  longer  part  of  the  kernel

Mount options for ext2

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

       acl / noacl
              Support POSIX Access Control Lists (or not).

       bsddf / minixdf
              Set  the  behaviour  for  the  statfs  system  call. The minixdf
              behaviour is to return in the f_blocks field the total number of
              blocks  of  the file system, while the bsddf behaviour (which is
              the default) is to subtract the overhead blocks used by the ext2
              file system 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  Check filesystem (block and inode bitmaps) at mount time.

       check=none / 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.

       debug  Print debugging info upon each (re)mount.

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

       grpid or bsdgroups / nogrpid or 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.

       grpquota / noquota / quota / usrquota
              These options are accepted but ignored.

       nobh   Do not attach buffer_heads to file pagecache. (Since 2.5.49.)

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

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

Mount options for ext3

       The  ‘ext3’  file system is a version of the ext2 file system which has
       been enhanced with journalling.  It supports the same options  as  ext2
       as well as the following additions:

              Update the ext3 file system’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 file system’s journal file;  ext3 will create
              a new journal, overwriting the old contents of  the  file  whose
              inode number is inum.

       noload Do not load the ext3 file system’s journal on mounting.

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

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

                     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  file  system  after  its  metadata  has   been
                     committed  to  the  journal.   This is rumoured to be the
                     highest-throughput option.  It guarantees  internal  file
                     system integrity, however it can allow old data to appear
                     in files after a crash and journal recovery.

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

Mount options for fat

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

       blocksize=512 / blocksize=1024 / blocksize=2048
              Set blocksize (default 512).

       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.

              Three different levels of pickyness can be chosen:

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

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

                     Like  "normal",  but names 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.

       conv=b[inary] / conv=t[ext] / conv=a[uto]
              The  fat  file system can perform CRLF<-->NL (MS-DOS text format
              to UNIX text format) conversion in  the  kernel.  The  following
              conversion 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
              conversion.   Several  people have had their data ruined by this
              translation. Beware!

              For file systems mounted  in  binary  mode,  a  conversion  tool
              (fromdos/todos) is available.

              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.

              Option passed to the CVF module.

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

       fat=12 / fat=16 / fat=32
              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.

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

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

Mount options for hfs

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

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

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

              Select  the  CDROM  session  to mount.  Defaults to leaving that
              decision to the  CDROM  driver.   This  option  will  fail  with
              anything but a CDROM as underlying device.

       part=n Select partition number n from the device.  Only makes sense for
              CDROMS.  Defaults to not parsing the partition table at all.

       quiet  Don’t complain about invalid mount options.

Mount options for hpfs

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

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

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

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

              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  file
       system (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
              available. Cf. map.

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

       uid=value and gid=value
              Give  all  files  in the file system the indicated user or group
              id, possibly overriding the information found in the Rock  Ridge
              extensions.  (Default: uid=0,gid=0.)

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

              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:

       conv=a[uto] / conv=b[inary] / conv=m[text] / conv=t[ext]
              (Default:  conv=binary.)   Since Linux 1.3.54 this option has no
              effect anymore.   (And  non-binary  settings  used  to  be  very
              dangerous, possibly leading to silent data corruption.)

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

              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 abends.

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

       errors=continue / errors=remount-ro / errors=panic
              Define the behaviour when  an  error  is  encountered.   (Either
              ignore  errors  and  just  mark  the  file  system erroneous and
              continue, or remount the file system  read-only,  or  panic  and
              halt the system.)

       noquota / quota / usrquota / grpquota
              These options are accepted but ignored.

Mount options for minix


Mount options for msdos

       See  mount  options  for  fat.   If  the  msdos  file system detects an
       inconsistency, it reports an error and sets the file system  read-only.
       The file system can be made writeable 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

       Instead of a textual option string, parsed by the kernel, the nfs  file
       system  expects  a  binary argument of type struct nfs_mount_data.  The
       program  mount  itself  parses  the  following  options  of  the   form
       ‘tag=value’,  and  puts  them  in  the  structure  mentioned:  rsize=n,
       wsize=n,  timeo=n,  retrans=n,  acregmin=n,   acregmax=n,   acdirmin=n,
       acdirmax=n,  actimeo=n,  retry=n,  port=n, mountport=n, mounthost=name,
       mountprog=n, mountvers=n, nfsprog=n, nfsvers=n, namlen=n.   The  option
       addr=n  is  accepted  but ignored.  Also the following Boolean options,
       possibly preceded by no are  recognized:  bg,  fg,  soft,  hard,  intr,
       posix, cto, ac, tcp, udp, lock.  For details, see nfs(5).

       Especially useful options include

              This  will make your nfs connection faster than with the default
              buffer size of 4096. (NFSv2 does not work with larger values  of
              rsize and wsize.)

       hard   The  program  accessing a file on a NFS mounted file system will
              hang when the server crashes. The process cannot be  interrupted
              or  killed unless you also specify intr.  When the NFS server is
              back online the program will continue undisturbed from where  it
              was. This is probably what you want.

       soft   This  option  allows the kernel to time out if the nfs server is
              not responding for some time. The time  can  be  specified  with
              timeo=time.   This  option  might  be  useful if your nfs server
              sometimes doesn’t respond or will be rebooted while some process
              tries  to  get  a  file from the server.  Usually it just causes
              lots of trouble.

       nolock Do not use locking. Do not start lockd.

Mount options for ntfs

              Character set to use when returning file  names.   Unlike  VFAT,
              NTFS  suppresses  names  that  contain unconvertible 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

              If enabled (posix=1),  the  file  system  distinguishes  between
              upper  and lower case. The 8.3 alias names are presented as hard
              links instead of being suppressed.

       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

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.  The reiserfs mount options are
       more fully described at

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

       hash=rupasov / hash=tea / hash=r5 / hash=detect
              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 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 file system has
                     huge directories and unusual file-name patterns.

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

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

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

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

       nolog  Disable  journalling.  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  journalling operations, save for
              actual writes into  its  journalling  area.   Implementation  of
              nolog is a work in progress.

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

              Replay the transactions which are in the  journal,  but  do  not
              actually mount the file system. 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

Mount options for romfs


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

       The  following  parameters  accept  a  suffix  k, m or g for Ki, Mi, Gi
       (binary kilo, mega and giga) and can be changed on remount.

              Override default maximum size of the filesystem.   The  size  is
              given  in  bytes, and rounded down to entire pages.  The default
              is half of the memory.

              Set number of blocks.

              Set number of inodes.

       mode=  Set initial permissions of the root directory.

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 file system 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

              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
                     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

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 illegal 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.

              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 be  enabled  for  the  filesystem
              with  this option.  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.

       The default is "lower".

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  file  system (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  file  system (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

              Sets  the  preferred  buffered  I/O  size (default size is 64K).
              size must be expressed as the logarithm (base2) of  the  desired
              I/O  size.   Valid  values  for  this  option are 14 through 16,
              inclusive (i.e. 16K, 32K, and 64K bytes).  On machines with a 4K
              pagesize,  13  (8K  bytes)  is also a valid size.  The preferred
              buffered I/O size can also be  altered  on  an  individual  file
              basis using the ioctl(2) system call.

       dmapi  /  xdsm
              Enable the DMAPI (Data Management API) event callouts.

              Set  the  number  of in-memory log buffers.  Valid numbers range
              from  2-8  inclusive.   The  default  value  is  8  buffers  for
              filesystems  with  a blocksize of 64K, 4 buffers for filesystems
              with a blocksize of  32K,  3  buffers  for  filesystems  with  a
              blocksize  of  16K,  and 2 buffers for all other configurations.
              Increasing the number of buffers  may  increase  performance  on
              some workloads at the cost of the memory used for the additional
              log buffers and their associated control structures.

              Set the size of each in-memory  log  buffer.   Valid  sizes  are
              16384  (16K)  and  32768  (32K).  The default value for machines
              with more than 32MB of  memory  is  32768,  machines  with  less
              memory use 16384 by default.

       logdev=device and rtdev=device
              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
              section or contained within it.  Refer to xfs(5).

              Data  allocations will not be aligned at stripe unit boundaries.

              Access timestamps are not updated when a file is read.

              The filesystem will be mounted without running log recovery.  If
              the  filesystem  was  not  cleanly unmounted, it is likely to be
              inconsistent when mounted in norecovery  mode.   Some  files  or
              directories  may not be accessible because of this.  Filesystems
              mounted norecovery must be mounted read-only or the  mount  will

       nouuid Ignore  the  filesystem  uuid.  This avoids errors for duplicate

              Make writes to files opened with the O_SYNC flag set  behave  as
              if  the  O_DSYNC flag had been used instead.  This can result in
              better performance without compromising data safety.  However if
              this  option  is in effect, timestamp updates from O_SYNC writes
              can be lost if the system crashes.

       quota / usrquota / uqnoenforce
              User disk quota  accounting  enabled,  and  limits  (optionally)

       grpquota / gqnoenforce
              Group  disk  quota  accounting  enabled  and limits (optionally)

       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.
              If this option is not specified and the filesystem was made on a
              stripe volume or the stripe width or unit were specified for the
              RAID device at mkfs  time,  then  the  mount  system  call  will
              restore the value from the superblock.  For filesystems that are
              made directly on RAID devices, these  options  can  be  used  to
              override  the  information  in  the superblock if the underlying
              disk layout changes after the filesystem has been created.   The
              swidth   option  is  required  if  the  sunit  option  has  been
              specified, and must be a multiple of the sunit value.

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.


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

         mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024

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

       This type of  mount  knows  about  10  options,  namely  loop,  offset,
       sizelimit,  encryption,  pseed,  phash,  loinit,  gpgkey,  gpghome  and
       itercountk that are really options to losetup(8).  (These  options  can
       be used in addition to those specific to the filesystem type.)

       If the mount requires a passphrase, you will be prompted for one unless
       you specify a file descriptor to read from instead with the -p  option.
       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.  If you are not so unwise as to make /etc/mtab a symbolic link to
       /proc/mounts then any loop device allocated by mount will be  freed  by
       umount.   You  can also free a loop device by hand, using ‘losetup -d’,
       see losetup(8).


       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 or missing nfs support in mount

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded


       /etc/fstab        file system table

       /etc/mtab         table of mounted file systems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try


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


       It is possible for a corrupted file system to cause a crash.

       Some Linux file systems don’t support -o sync and -o dirsync (the  ext2
       and  ext3  file  systems 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).

       Mount by label or uuid will work only if your devices  have  the  names
       listed  in  /proc/partitions.   In  particular, it may well fail if the
       kernel was compiled with devfs but devfs is not mounted.


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