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.

       The listing and help.
              Three forms of invocation do not actually mount anything:

              mount -h
                     prints a help message

              mount -V
                     prints a version string

              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
              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

              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 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) 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.

              When  the  proc  filesystem is mounted (say at /proc), the files
              /etc/mtab and /proc/mounts have very similar contents. The  for-
              mer  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 using the "user"
              option will fail.

                     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
              those  on  the  original  mount  point, and cannot be changed by
              passing the -o  option  along  with  --bind/--rbind.  The  mount
              options  can be changed by a separate remount command, for exam-

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

              Note that behavior of  the  remount  operation  depends  on  the
              /etc/mtab  file. The first command stores the 'bind' flag to the
                     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

       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.

                     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

       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.

              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
              Don't  call  the  /sbin/mount.<filesystem>  helper  even  if  it

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

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

              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 absolut paths.

       -p, --pass-fd num
              In  case  of  a  loop mount with encryption, read the passphrase
              from file descriptor num instead of from the terminal.

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

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

       -U uuid
              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 usbdevfs.  Note,
              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
              '' 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.

              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.

       -O, --test-opts opts
              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 com-

                     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

       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, 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-
              tatime and reatime mount options.

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

       auto   Can be mounted with the -a option.
              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 con-

              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 because vis-
              able to userspace. This was found to be useful for  things  like
              stateless linux.

              Note  that  kernel rejects any remount request that includes the
              context option even if unchanged from the current context.

              For more details, see selinux(8)

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

       dev    Interpret character or block special devices on the filesystem.

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

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

              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).

              Specifies  an  encryption algorithm to use.  Used in conjunction
              with the loop option.

              Specifies the key size to use for an encryption algorithm.  Used
              in  conjunction with the loop and encryption options.  nofail Do
              not report errors for this device if it does not  exist.   iver-
              sion  Every time the inode is modified, the i_version field will
              be incremented.

              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

              Update inode access times relative to  modify  or  change  time.
              Access time is only updated if the previous access time was 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-

              Since Linux 2.6.30, the kernel defaults to the behavior provided
              by this option (unless noatime was  specified), and the stricta-
              time  option  is  required  to  obtain traditional semantics. In
              addition, since Linux 2.6.30, the file's  last  access  time  is
              always  updated  if  it  is more than 1 day old.

              Do  not  use  relatime  feature.  See also the strictatime mount

              Allows to explicitly requesting full atime updates.  This  makes
              it  possible  for  kernel to defaults to relatime or noatime but
              still allow userspace to override it. For more details about the

       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.

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

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

       users  Allow every user to mount  and  unmount  the  filesystem.   This
              option  implies  the  options  noexec, nosuid, and nodev (unless
              overridden  by  subsequent  options,  as  in  the  option   line

              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
              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.

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

       The debugfs filesystem is a pseudo filesystem, traditionally mounted on
       /sys/kernel/debug.  There are no mount options.

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

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

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

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

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

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

              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

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

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

              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.

              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.

              These options are accepted but ignored.

              Disables 32-bit UIDs and GIDs.   This  is  for  interoperability

       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).

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

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

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

              When the external  journal  device's  major/minor  numbers  have
              changed,  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 journalling  mode  for  file  data.   Metadata  is
              always  journaled.   To use modes other than ordered on the root
              filesystem, pass the mode to the kernel as boot parameter,  e.g.

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

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

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

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 and usrquota are backwardly compatible with ext3 or ext2.

              Enable checksumming of  the  journal  transactions.   This  will
              allow  the recovery code in e2fsck and the kernel to detect 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.

              Update the ext4 filesystem's journal to the current format.

       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

              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.

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

              Maximum  amount of time ext4 should wait for additional filesys-
              tem operations to be batch together  with  a  synchronous  write
              operation. Since a synchronous write operation is going to force
              a commit and then a wait for the I/O complete, it  doesn't  cost
              much,  and  can  be  a  huge throughput win, we wait for a small
              amount of time to see if any other transactions can piggyback on
              the  synchronous  write. The algorithm used is designed to auto-
              matically tune for the speed  of  the  disk,  by  measuring  the
              amount of time (on average) that it takes to finish committing a
              transaction. Call this time the "commit time".  If the time that
              the  transaction  has been running is less than the commit time,
              ext4 will try sleeping for the commit time to see if other 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  priorty)
              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("")/write(fd,..)/close(fd)/  rename("",
              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.

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

       resize Allows  to  resize  filesystem  to  the end of the last existing
              block group, further resize has to be done with resize2fs either
              online,  or  offline.  It can be used only with conjunction with

              This options allows to enables/disables the  in-kernel  facility
              for  tracking  filesystem  metadata  blocks within internal data
              structures. This allows multi- block allocator  and  other  rou-
              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.)
              umask of the current process.  The value is given in octal.

              This option controls the permission check of mtime/atime.

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

              2      Other users can change timestamp.

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

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

              Three different levels of pickyness can be chosen:

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

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

                     Like  "normal",  but names 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,

              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.

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

              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 file-
              names are stored on disk in Unicode format.

       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.

              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  any-
              thing 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.

              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).

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

              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:

              (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
              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 pre-
              viously specified in order to restore normal behavior.

              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.)

              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-common 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.

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

       uid=value, gid=value and umask=value
              Set  the  file permission on the filesystem.  The umask value is
              given in octal.  By default, the files are owned by root and not
              readable by somebody else.

Mount options for proc
       uid=value and gid=value
              These options are recognized, but have no effect as far as I can

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-

              Rupasov.  This may provide performance improvements in some sit-

       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 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-
              half of the memory. The size parameter also accepts a  suffix  %
              to limit this tmpfs instance to that percentage of your physical
              RAM: the default, when neither size nor nr_blocks is  specified,
              is size=50%

              The same as size, but in blocks of PAGE_CACHE_SIZE

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

       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
              ubiX_Y UBI device number X, volume number Y

              ubiY   UBI device number 0, volume number Y

                     UBI device number X, volume with name NAME

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

       The following mount options are available:

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

              Do not bulk-read. This is the default.

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

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

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

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

              Show deleted files in lists.
              Set the CDROM session counting from 0. Default: last session.

              Override standard anchor location. Default: 256.

              Override the VolumeDesc location. (unused)

              Override the PartitionDesc location. (unused)

              Set the last block of the filesystem.

              Override the fileset block location. (unused)

              Override the root directory location. (unused)

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

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

              44bsd  For  filesystems  created  by  a  BSD-like  system  (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

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 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
              uid=gid=0, mode=0444). The mode is given in octal.

Mount options for xenix

Mount options for xfs
              Sets  the buffered I/O end-of-file preallocation size when doing
              delayed allocation writeout (default size is 64KiB).  Valid val-
              ues  for  this  option are page size (typically 4KiB) through to
              1GiB, inclusive, in power-of-2 increments.

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

              Enables  the  use  of block layer write barriers for writes into
              the journal and unwritten extent conversion.   This  allows  for
              drive  level  write caching to be enabled, for devices that sup-
              port write barriers.

       dmapi  Enable the DMAPI (Data Management API) event callouts.  Use with
              the mtpt option.

       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.

              Sets the number of hash buckets available for  hashing  the  in-
              memory  inodes of the specified mount point.  If a value of zero
              is used, the value selected by the  default  algorithm  will  be
              displayed in /proc/mounts.

              When  inode  clusters are emptied of inodes, keep them around on
              the disk (ikeep) - this is the traditional XFS behaviour and  is
              still  the  default  for  now.   Using the noikeep option, inode
              clusters are returned to the free space pool.

              Indicates that XFS is allowed to create inodes at  any  location
              in  the  filesystem,  including those which will result in inode
              If  neither  of these two options are specified, then filesystem
              will behave 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 for any
              recent kernel.

              Set the size of each in-memory log buffer.  Size may  be  speci-
              fied  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  default  value  for  any
              recent kernel is 32768.

       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 sec-
              tion or contained within it.  Refer to xfs(5).

              Use  with  the  dmapi  option.  The value specified here will be
              included in the DMAPI mount event, and should be the path of the
              actual mountpoint that is used.

              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 Don't check for double mounted filesystems using the  filesystem
              uuid.  This is useful to mount LVM snapshot volumes.

              Make  O_SYNC writes implement true O_SYNC.  WITHOUT this option,
              Linux XFS behaves as if an osyncisdsync option  is  used,  which
              will 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 not in effect, timestamp updates  from  O_SYNC
              writes  can be lost if the system crashes.  If timestamp updates
              are critical, use the osyncisosync option.

       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  speci-
              fied, and must be a multiple of the sunit value.

              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.

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

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

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

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

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

              mount /tmp/disk.img /mnt

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

       This type of mount knows about four options, namely loop, offset, size-
       limit and encryption, that are really options to  losetup(8).   If  the
       mount  requires  a  passphrase, you will be prompted for one unless you
       specify a file descriptor to  read  from  instead  with  the  --pass-fd
       option.   (These  options  can be used in addition to those specific to

       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 syntax of external mount helpers is:

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

       where the <type> is filesystem type and -sfnvo options have same  mean-
       ing like standard mount options. The -t option is used  for filesystems
       with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs).

       /etc/fstab        filesystem table

       /etc/mtab         table of mounted filesystems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try

       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 filesystem to cause a crash.

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

       The -o remount may not be able to change mount parameters (all  ext2fs-
       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

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

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

util-linux                       December 2004                        MOUNT(8)
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