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       mount - mount a filesystem


       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 several devices. The mount command serves
       to  attach  the  filesystem  found  on  some  device to the big file tree. Conversely, the
       umount(8) command will detach it again.

       The standard form of the mount command, is

              mount -t type device dir

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

       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 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).

              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
              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

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

       The shared subtrees operations.
              Since Linux 2.6.15 it is possible to mark a mount  and  its  submounts  as  shared,
              private,  slave or unbindable. A shared mount provides 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 master, but any not vice-
              versa.  A private mount carries no propagation abilities.  A unbindable mount is  a
              private  mount  which cannot cloned through a bind operation. Detailed semantics is
              documented in Documentation/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 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 below).

              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 simultaneously.

              When mounting a filesystem mentioned in fstab or mtab, it suffices 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.

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

              Thus, given a line

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

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

                     mount /dev/cdrom


                     mount /cd

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


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

       Command line 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  filesystem.   This  option  is  useful in
              conjunction with the -v flag to determine what the mount command is trying  to  do.
              It  can  also be used to add entries for devices that were mounted earlier with the
              -n option. The -f option checks for existing record in /etc/mtab and fails when the
              record already exists (with regular non-fake mount, this check is done by kernel).

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

       -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
              reiserfs using reiserfstune(8).

       -n     Mount without writing in /etc/mtab.  This is necessary for example 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 absolute paths.

       -s     Tolerate  sloppy  mount options rather than failing. This will ignore mount options
              not supported by a filesystem type. Not all filesystems support this  option.  This
              option exists for support of the Linux autofs-based automounter.

       -r     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     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
              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  filesystem  type.   The
              filesystem  types  which are currently supported include: adfs, affs, autofs, cifs,
              coda, coherent, cramfs, debugfs, devpts, efs, ext, ext2, ext3, ext4, hfs,  hfsplus,
              hpfs,  iso9660,  jfs,  minix,  msdos,  ncpfs,  nfs,  nfs4, 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 usbdevfs.  Note, the real list of all supported filesystems depends on
              your kernel.

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

              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     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 command:

                     mount -a -O no_netdev

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

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

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

                     mount -a -t ext2 -O _netdev

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

       -o     Options  are  specified  with  a  -o  flag  followed by a comma separated string of
              options. For example:
                     mount LABEL=mydisk -o noatime,nouser

              MOUNT OPTIONS sections.

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

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

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


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

       Some  of  these  options  could be enabled or disabled by default in the system kernel. To
       check the current setting see the options in /proc/mounts.

       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

       atime  Update inode access time for each access. See also the strictatime mount option.

              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.

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

       context=context, fscontext=context, defcontext=context and rootcontext=context
              The  context=  option  is  useful  when  mounting  filesystems  that do not support
              extended attributes, such as a floppy or hard disk formatted with VFAT, or  systems
              that  are not normally running under SELinux, such as an ext3 formatted disk from a
              non-SELinux workstation. You can also use context= on filesystems you do not trust,
              such  as a floppy. It also helps in compatibility with xattr-supporting filesystems
              on earlier 2.4.<x> kernel versions. Even where xattrs are supported, you  can  save
              time  not  having  to  label  every  file by assigning the entire disk one security

              A      commonly      used      option      for       removable       media       is

              Two  other  options  are  fscontext=  and  defcontext=,  both of which are mutually
              exclusive of the context option. This means you can use  fscontext  and  defcontext
              with each other, but neither can be used with context.

              The fscontext= option works for all filesystems, regardless of their xattr support.
              The fscontext option sets the overarching filesystem label to a  specific  security
              context. This filesystem label is separate from the individual labels on the files.
              It represents the entire filesystem for certain kinds of permission checks, such as
              during  mount or file creation.  Individual file labels are still obtained from the
              xattrs on the files themselves. The context  option  actually  sets  the  aggregate
              context  that  fscontext  provides,  in  addition  to  supplying the same label for
              individual files.

              You can set the default security context  for  unlabeled  files  using  defcontext=
              option. This overrides the value set for unlabeled files in the policy and requires
              a filesystem that supports xattr labeling.

              The rootcontext= option allows you to explicitly label the root inode of a FS being
              mounted  before that FS or inode because visable to userspace. This was found to be
              useful for things like stateless linux.

              For more details, see selinux(8)

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

       dev    Interpret character or block special devices on the filesystem.

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

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

              Do not update directory inode access times on this filesystem.

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

       exec   Permit execution of binaries.

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

       group  Allow an ordinary (i.e., non-root) user to mount  the  filesystem  if  one  of  his
              groups matches the group of the device.  This option implies the options nosuid and
              nodev  (unless  overridden  by  subsequent  options,  as   in   the   option   line

              Every time the inode is modified, the i_version field will be incremented.

              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

              Update  inode  access times relative to modify or change time.  Access time is only
              updated if the previous access time was earlier than the current modify  or  change
              time.  (Similar  to noatime, but doesn't break mutt or other applications that need
              to know if a file has been read since the last time it was modified.)

              Do not use relatime feature. See also the strictatime mount option.

              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 default system mount options see /proc/mounts.

              Use the kernel's default behaviour for inode access time updates.

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

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

       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 commonly used to change
              the mount flags  for  a  filesystem,  especially  to  make  a  readonly  filesystem
              writeable. 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 command 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

       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 filesystem.  This is the

       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 users,exec,dev,suid).


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

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

Mount options for adfs

       uid=value and gid=value
              Set the owner and group of the files in the filesystem (default: uid=gid=0).

       ownmask=value and othmask=value
              Set the permission mask for  ADFS  'owner'  permissions  and  'other'  permissions,
              respectively    (default:    0700    and    0077,    respectively).     See    also

Mount options for affs

       uid=value and gid=value
              Set the owner and group of the root of the filesystem (default: uid=gid=0, but with
              option  uid  or gid without specified value, the uid and gid of the current process
              are taken).

       setuid=value and setgid=value
              Set the owner and group of all files.

              Set the mode of all files to value & 0777 disregarding  the  original  permissions.
              Add search permission to directories that have read permission.  The value is given
              in octal.

              Do not allow any changes to the protection bits on the filesystem.

       usemp  Set uid and gid of the root of the filesystem to the uid and gid of the mount point
              upon the first sync or umount, and then clear this option. Strange...

              Print an informational message for each successful mount.

              Prefix used before volume name, when following a link.

              Prefix (of length at most 30) used before '/' when following a symbolic link.

              (Default: 2.) Number of unused blocks at the start of the device.

              Give explicitly the location of the root block.

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

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

Mount options for cifs

       See the options section  of  the  mount.cifs(8)  man  page  (cifs-mount  package  must  be

Mount options for coherent


Mount options for debugfs

       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

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

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

              To use this option effectively, /dev/ptmx must be a symbolic link to pts/ptmx.  See
              Documentation/filesystems/devpts.txt in the linux kernel source tree for details.


              Set the mode for the new ptmx device node in the devpts filesystem.

              With  the  support for multiple instances of devpts (see newinstance option above),
              each instance has a private  ptmx  node  in  the  root  of  the  devpts  filesystem
              (typically /dev/pts/ptmx).

              For  compatibility  with  older versions of the kernel, the default mode of the new
              ptmx node is 0000.  ptmxmode=value specifies a more useful mode for the  ptmx  node
              and is highly recommended when the newinstance option is specified.

              This  option  is  only  implemented  in linux kernel versions starting with 2.6.29.
              Further this option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in
              the kernel configuration.

Mount options for ext

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

Mount options for ext2

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

              Support POSIX Access Control Lists (or not).

              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 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 continue, or remount the filesystem read-only, or
              panic  and  halt the system.)  The default is set in the filesystem superblock, and
              can be changed using tune2fs(8).

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

              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 default.

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

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

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

Mount options for ext3

       The ext3 filesystem is a version of the ext2  filesystem  which  has  been  enhanced  with
       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. Otherwise, it specifies the
              number of the inode which will represent the ext3 filesystem's journal file;   ext3
              will  create  a  new  journal, overwriting the old contents of the file whose inode
              number is inum.

       noload Do not load the ext3 filesystem's journal on mounting.

              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.  rootflags=data=journal.

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

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

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

       barrier=0 / barrier=1
              This enables/disables barriers.  barrier=0 disables it, barrier=1 enables it.   The
              ext3 filesystem does not enable write barriers by default.

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

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

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

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

              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 barriers enforce proper on-disk ordering of journal commits, making
              volatile disk write caches safe to use, at some performance penalty.  If your disks
              are battery-backed in one way or another, disabling  barriers  may  safely  improve
              performance.   The  mount  options  "barrier"  and  "nobarrier" can also be used to
              enable or disable barriers, for consistency with other ext4 mount options.

              The ext4 filesystem enables write barriers by default.

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

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

              Deferring block allocation until write-out time.

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

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

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

              The I/O priority (from 0 to 7, where 0 is the highest 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.

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

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

              or worse yet

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

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

Mount options for fat

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

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

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

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

              Set the umask applied to directories only.  The default is the umask of the current
              process.  The value is given in octal.

              Set the umask applied to regular files only.  The  default  is  the  umask  of  the
              current process.  The value is given in octal.

              This option controls the permission check of mtime/atime.

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

              2      Other users can change timestamp.

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

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

              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 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, dvi).

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

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

              Forces the driver to use the CVF (Compressed Volume File) module cvf_module instead
              of  auto-detection.  If  the  kernel  supports kmod, the cvf_format=xxx option also
              controls on-demand CVF module loading.  This option is obsolete.

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

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

              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

       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  particuluarly
              useful when mounting devices (like digital cameras) that are set to UTC in order to
              avoid the pitfalls of local time.

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

              If  set,  the  execute  permission  bits  of  the  file will be allowed only if the
              extension part of the name is .EXE, .COM, or .BAT. Not set by default.

              If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux.   Not  set
              by default.

       flush  If  set,  the filesystem will try to flush to disk more early than normal.  Not set
              by default.

              Use the "free clusters" value stored on FSINFO. It'll be used to  determine  number
              of  free  clusters  without  scanning  disk.  But it's not used by default, because
              recent Windows don't update it correctly in some case. If you are  sure  the  "free
              clusters" on FSINFO is correct, by this option you can avoid scanning disk.

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

Mount options for hfs

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

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

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

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

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

       quiet  Don't complain about invalid mount options.

Mount options for hpfs

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

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

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

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

              Do not abort mounting when certain consistency checks fail.

Mount options for iso9660

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

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

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

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

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

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

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

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

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

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

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

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

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

              Character  set  to  use  for  converting  16  bit Unicode characters on CD to 8 bit
              characters. The default is iso8859-1.

       utf8   Convert 16 bit Unicode characters on CD to UTF-8.

Mount options for jfs

              Character set to use for converting from Unicode to ASCII.  The default is to do no
              conversion.    Use   iocharset=utf8   for   UTF8   translations.    This   requires
              CONFIG_NLS_UTF8 to be set in the kernel .config file.

              Resize the volume to  value  blocks.  JFS  only  supports  growing  a  volume,  not
              shrinking  it.  This  option  is  only  valid  during a remount, when the volume is
              mounted read-write. The resize keyword with no value will grow the  volume  to  the
              full size of the partition.

              Do not write to the journal.  The primary use of this option is to allow for higher
              performance when restoring a volume from backup media. The integrity of the  volume
              is not guaranteed if the system abnormally 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.

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

              These options are accepted but ignored.

Mount options for minix


Mount options for msdos

       See  mount  options for fat.  If the msdos filesystem detects an inconsistency, it reports
       an error and sets the file system read-only. The filesystem can be made 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 and nfs4

       See the options section of the nfs(5) man page (nfs-utils package must be installed).

       The nfs and nfs4 implementation expects a binary argument (a struct nfs_mount_data) to the
       mount system call. This argument is constructed by mount.nfs(8) and the current version of
       mount (2.13) does not know anything about nfs and nfs4.

Mount options for ntfs

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

              New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

              For 0 (or `no' or `false'),  do  not  use  escape  sequences  for  unknown  Unicode
              characters.   For  1  (or  `yes'  or  `true')  or  2,  use vfat-style 4-byte escape
              sequences starting with  ":".  Here  2  give  a  little-endian  encoding  and  1  a
              byteswapped bigendian encoding.

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

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

Mount options for proc

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

Mount options for ramfs

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

Mount options for reiserfs

       Reiserfs is a journaling filesystem.

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

              Choose which hash function reiserfs will use to find files within directories.

                     A  hash  invented  by  Yury Yu. Rupasov.  It is fast and preserves locality,
                     mapping lexicographically close file  names  to  close  hash  values.   This
                     option  should  not  be  used,  as  it  causes  a  high  probability of hash

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

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

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

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

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

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

       nolog  Disable  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

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

              Replay  the  transactions  which  are in the journal, but do not actually mount the
              filesystem. Mainly used by reiserfsck.

              A remount option which permits online expansion of reiserfs partitions.   Instructs
              reiserfs  to assume that the device has number blocks.  This option is designed for
              use with devices which are under logical  volume  management  (LVM).   There  is  a
              special      resizer      utility      which      can      be     obtained     from

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

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

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

              Override default maximum size of the filesystem.  The size is given in  bytes,  and
              rounded  up to entire pages.  The default is half of the memory. The size parameter
              also accepts a suffix % to limit this tmpfs instance to  that  percentage  of  your
              physical  RAM:  the  default,  when  neither  size  nor  nr_blocks is specified, is

              The same as size, but in blocks of PAGE_CACHE_SIZE

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

       The tmpfs mount options for sizing ( size, nr_blocks, and nr_inodes) accept a suffix k,  m
       or g for Ki, Mi, Gi (binary kilo, 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 example, mpol=bind:0-3,5,7,9-15

              Note  that  trying  to  mount  a tmpfs with an mpol option will fail if the running
              kernel does not support NUMA; and will fail if its nodelist specifies a node  which
              is not online.  If your system relies on that tmpfs being mounted, but from time to
              time runs a kernel built without NUMA capability (perhaps a safe recovery  kernel),
              or  with  fewer  nodes  online,  then  it is advisable to omit the mpol option from
              automatic mount options.  It can be added later, when the tmpfs is already  mounted
              on MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.

Mount options for udf

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

              Show deleted files in lists.

              Unset strict conformance.

              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

              Override standard anchor location. Default: 256.

              Override the VolumeDesc location. (unused)

              Override the PartitionDesc location. (unused)

              Set the last block of the filesystem.

              Override the fileset block location. (unused)

              Override the root directory location. (unused)

Mount options for ufs

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

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

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

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

                     For filesystems  created  by  OpenStep  (currently  read  only).   The  same
                     filesystem type is also used by Mac OS X.

              Set 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 umsdos.

Mount options for vfat

       First of all, the mount options for fat are recognized.  The dotsOK option  is  explicitly
       killed by vfat.  Furthermore, there are

              Translate unhandled Unicode characters to special escaped sequences.  This lets you
              backup and restore filenames that are created with any Unicode characters.  Without
              this option, a '?' is used when no translation is possible. The escape character is
              ':' because it is otherwise 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 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. This mode is the default.

              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.

Mount options for usbfs

       devuid=uid and devgid=gid and devmode=mode
              Set the owner and group and mode of  the  device  files  in  the  usbfs  filesystem
              (default: uid=gid=0, mode=0644). The mode is given in octal.

       busuid=uid and busgid=gid and busmode=mode
              Set  the  owner  and  group and mode of the bus directories in the usbfs filesystem
              (default: uid=gid=0, mode=0555). The mode is given in octal.

       listuid=uid and listgid=gid and listmode=mode
              Set the owner  and  group  and  mode  of  the  file  devices  (default:  uid=gid=0,
              mode=0444). The mode is given in octal.

Mount options for xenix


Mount options for xfs

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

              The options enable/disable (default is disabled for backward compatibility on-disk)
              an "opportunistic" improvement to be made in the way inline extended attributes are
              stored  on-disk.   When  the  new  form  is  used for the first time (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 support 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 numbers occupying more than 32  bits  of
              significance.   This  is  provided for backwards compatibility, but causes problems
              for backup applications that cannot handle large inode numbers.

              If nolargeio is specified, the optimal I/O reported in st_blksize by  stat(2)  will
              be   as  small  as  possible  to  allow  user  applications  to  avoid  inefficient
              read/modify/write I/O.  If largeio is specified, a filesystem  that  has  a  swidth
              specified  will return the swidth value (in bytes) in st_blksize. If the filesystem
              does not have a swidth specified but does specify an allocsize then  allocsize  (in
              bytes)  will  be  returned instead.  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 filesystems with a blocksize of 64KiB, 4 buffers
              for filesystems with a blocksize  of  32KiB,  3  buffers  for  filesystems  with  a
              blocksize  of  16KiB  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.  Size may be specified in bytes, or in
              kilobytes with a "k" suffix.  Valid sizes for version 1  and  version  2  logs  are
              16384  (16k)  and  32768  (32k).  Valid sizes for version 2 logs also include 65536
              (64k), 131072 (128k) and 262144 (256k).  The default value for machines  with  more
              than 32MiB 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).

              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 fail.

       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.

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

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

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

       sunit=value and swidth=value
              Used  to  specify  the  stripe unit and width for a RAID device or a stripe volume.
              value must be specified in 512-byte block units.  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.

              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/fdimage /mnt -t vfat -o loop=/dev/loop3

       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 11 options, namely loop, offset, sizelimit, encryption,
       pseed, phash, loinit, gpgkey, gpghome, cleartextkey and itercountk that are really options
       to losetup(8).  (These options can be used in addition to those specific to the filesystem

       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 command line option, or specify a file name
       with cleartextkey mount 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

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

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


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

       0      success

       1      incorrect invocation or permissions

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

       4      internal mount bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded


       The syntax of external mount helpers is:

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

       where  the  <suffix> is filesystem type and -sfnvo options have same meaning like standard
       mount options.


       /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), losetup(8)


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

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

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

       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.

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

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


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


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