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MOUNT(8)                              System Administration                              MOUNT(8)

       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 invis-
       ible, and as long as this filesystem remains mounted, the pathname dir refers to the  root
       of the filesystem on device.

       If only directory or device is given, for example:

              mount /dir

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

              mount --target /mountpoint

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

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

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

       The device indication.
              Most  devices  are  indicated  by  a  file  name  (of a block special 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 filesystem LABEL or UUID (see the -L and -U options below)
              and  partition  PARTUUID or PARTLABEL (partition identifiers are supported for GUID
              Partition Table (GPT) and MAC partition tables only).

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

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

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

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

              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 indi-
              cated, 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.

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

                     mount /dev/foo /dir

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

                     mount device|dir -o <options>

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

              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 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 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  sub-
              mounts.  The  entire  file hierarchy including submounts is attached a second place

                     mount --rbind olddir newdir

              or shortoption

                     mount -R olddir newdir

              Note that the filesystem mount options will remain the same as those on the  origi-
              nal mount point.

              mount(8) since v2.27 (backported to RHEL7.3) allow to change the options by passing
              the -o option along with --bind for example:

                     mount --bind,ro foo foo

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

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

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

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

              It's  impossible  to  change  mount  options  recursively  (for  example  with   -o

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

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

       The shared subtrees operations.
              Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, pri-
              vate, 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 be cloned through a bind operation.  Detailed  semantics
              is  documented  in  Documentation/filesystems/sharedsubtree.txt  file in the kernel
              source tree.

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

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

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

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

              Note that Linux kernel does not allow to  change  more  propagation  flags  by  one
              mount(2) syscall and the flags cannot be mixed with another mount options.

              Since  util-linux  2.23 mount command allows to use more propagation flags together
              and with another mount operations. This feature is EXPERIMENTAL.   The  propagation
              flags  are  applied by additional mount(2) syscalls after previous successful mount
              operation. Note that this use case is not atomic. The propagation flags is possible
              to  specify in fstab(5) as mount options (private, slave, shared, unbindable, rpri-
              vate, rslave, rshared, runbindable).

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

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

       The full set of mount options used by an  invocation  of  mount  is  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, --version
              Output version.

       -h, --help
              Print a help message.

       -v, --verbose
              Verbose mode.

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

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

       -f, --fake
              Causes  everything  to be done except for the actual system call; if it's not obvi-
              ous, 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, --internal-only
              Don't call the /sbin/mount.<filesystem> helper even if it exists.

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

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

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

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

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

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

              Note that, depending on the filesystem type, state and kernel behavior, the  system
              may still write to the device. For example, Ext3 or ext4 will replay its journal if
              the filesystem is dirty. To prevent this kind of write  access,  you  may  want  to
              mount  ext3  or  ext4  filesystem  with  "ro,noload" mount options or set the block
              device to read-only mode, see command blockdev(8).

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

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

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

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

              Note  that mount(8) does not pass the option --fstab to /sbin/mount.<type> helpers,
              it means that the alternative fstab files will be invisible for the  helpers.  This
              is no problem for normal mounts, but user (non-root) mounts always require fstab to
              verify user's rights.

       -t, --types 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, reis-
              erfs, romfs, squashfs, smbfs, sysv, tmpfs, ubifs, 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.

              The  programs mount and umount support filesystem subtypes.  The subtype is defined
              by '.subtype' suffix.  For example  'fuse.sshfs'. It's recommended to  use  subtype
              notation  rather  than add any prefix to the mount source (for example 'sshfs#exam-
    ' 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 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 library for guessing the  filesystem  type;
              if  that  does not turn up anything that looks familiar, mount will try to read the
              file /etc/filesystems, or, if that does not exist, /proc/filesystems.  All  of  the
              filesystem  types  listed  there  will  be tried, except for those that are labeled
              "nodev" (e.g., devpts, proc and nfs).  If /etc/filesystems ends in a  line  with  a
              single  * only, mount will read /proc/filesystems afterwards. All of the filesystem
              types will be mounted with mount option "silent".

              The  auto  type  may  be  useful  for  user-mounted  floppies.   Creating  a   file
              /etc/filesystems  can be useful to change the probe order (e.g., to try vfat before
              msdos or ext3 before ext2) or if you use a kernel module autoloader.

              More than one type may be specified  in  a  comma  separated  list.   The  list  of
              filesystem  types  can be prefixed with no to specify the filesystem types on which
              no action should be taken.  (This can be meaningful with the -a option.) For  exam-
              ple, the command:

                     mount -a -t nomsdos,ext

              mounts all filesystems except those of type msdos and ext.

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

       -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 command:

                     mount -a -O no_netdev

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

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

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

                     mount -a -t ext2 -O _netdev

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

       -o, --options opts
              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.  Note that filesystems also
       have per-filesystem specific default mount options (see for example tune2fs -l output  for
       extN filesystems).

       The  following  options  apply  to  any  filesystem  that  is being mounted (but not every
       filesystem actually honors them - e.g., the sync option today has effect  only  for  ext2,
       ext3, fat, vfat and ufs):

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

       atime  Do not use noatime feature, then the inode access  time  is  controlled  by  kernel
              defaults. See also the description for strictatime and relatime mount options.

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

       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 con-

              A commonly used option for  removable  media  is  context="system_u:object_r:remov-

              Two other options are fscontext= and defcontext=, both of which are mutually exclu-
              sive 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 con-
              text  that fscontext provides, in addition to supplying the same label for individ-
              ual files.

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

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

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

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

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

              For more details, see selinux(8).

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

              Note  that  the  real  set  of  the all default mount options depends on kernel and
              filesystem type. See the begin of this section for more details.

       dev    Interpret character or block special devices on the filesystem.

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

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

              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.)

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

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

              Allows to explicitly requesting full atime updates. This makes it possible for ker-
              nel 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.)

       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 commonly used to  change
              the  mount  flags  for  a  filesystem,  especially  to  make  a readonly filesystem
              writable. It does not change device or mount point.

              The remount functionality follows the standard way 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 lim-
              ited 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).

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

              Allow to make a target directory (mountpoint). The optional argument <mode>  speci-
              fies  the file system access mode used for mkdir (2) in octal notation. The default
              mode is 0755. This functionality is supported only for root users.

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

       What options are supported depends a bit on the running kernel.  More info may be found in
       the kernel source subdirectory 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 /usr/src/linux/Docu-

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-utils  package  must  be

Mount options for coherent

Mount options for debugfs
       The debugfs filesystem is a pseudo filesystem, traditionally mounted on /sys/kernel/debug.
       As of kernel version 3.4, debugfs has the following options:

       uid=n, gid=n
              Set the owner and group of the mountpoint.

              Sets the mode of the mountpoint.

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

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

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

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

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

              This  option is mainly used to support containers in the linux kernel. It is imple-
              mented 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 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 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  (typi-
              cally /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. Fur-
              ther 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.)

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

       debug  Print debugging info upon each (re)mount.

              Define the 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.

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

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

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

       resgid=n and resuid=n
              The ext2 filesystem reserves a  certain  percentage  of  the  available  space  (by
              default 5%, see mke2fs(8) and tune2fs(8)).  These options determine who can use the
              reserved blocks.  (Roughly: whoever has the specified uid, or belongs to the speci-
              fied 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 jour-
       naling.  It supports the same options as ext2 as well as the following additions:

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

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

              When  the  external  journal device's major/minor numbers have changed, this option
              allows the user to specify the new journal location.  The journal device is identi-
              fied 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  incon-
              sistencies that can lead to any number of problems.

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

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

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

                     Data  ordering is not preserved - data may be written into the main filesys-
                     tem 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.
              Write barriers enforce proper on-disk ordering 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 barriers unless  your
              disks are battery-backed one way or another.  Otherwise you risk filesystem corrup-
              tion in case of power failure.

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

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

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

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

Mount options for ext4
       The ext4 filesystem is an advanced level of the ext3 filesystem which incorporates  scala-
       bility and reliability enhancements for supporting large filesystem.

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

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

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

       barrier=0 / barrier=1 / barrier / nobarrier
              This enables/disables the use of write barriers in the jbd  code.   barrier=0  dis-
              ables,  barrier=1 enables.  This also requires an IO stack which can support barri-
              ers, 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  value
              must be a power of 2. The default value is 32 blocks.

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

              Deferring block allocation until write-out time.

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

              Maximum amount of time ext4 should wait for additional filesystem operations to  be
              batch together with a synchronous write operation. Since a synchronous write opera-
              tion is going to force a commit and then a wait for the I/O  complete,  it  doesn't
              cost  much, and can be a huge throughput win, we wait for a small amount of time to
              see if any other transactions can piggyback on the synchronous write. The algorithm
              used  is designed to automatically tune for the speed of the disk, by measuring the
              amount of time (on average) that it takes to finish committing a transaction.  Call
              this  time the "commit time".  If the time that the transaction has been running is
              less than the commit time, ext4 will try sleeping for the commit  time  to  see  if
              other  operations  will  join  the  transaction.  The  commit time is capped by the
              max_batch_time, which defaults to 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  priority)  which  should  be
              used  for  I/O  operations submitted by kjournald2 during a commit operation.  This
              defaults to 3, which is a slightly higher priority than the default I/O priority.

       abort  Simulate the effects of calling ext4_abort() for debugging purposes.  This is  nor-
              mally used while remounting a filesystem which is already mounted.

              Many  broken  applications don't use fsync() when replacing existing files via pat-
              terns 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 commit-
              ted.  This provides roughly the same level of guarantees as ext3,  and  avoids  the
              "zero-length"  problem  that  can  happen  when a system crashes before the delayed
              allocation blocks are forced to disk.

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

              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 remount.

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

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

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

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

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

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

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

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

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

              This option controls the permission check of mtime/atime.

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

              2      Other users can change timestamp.

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

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

              Three different levels of pickyness can be chosen:

                     Upper and lower case are accepted and equivalent, long name parts are  trun-
                     cated (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 filesys-
              tems. 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 avail-
              able. 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 con-
              trols 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 inconsis-

              If set, causes discard/TRIM commands to be issued to the block device  when  blocks
              are freed. This is useful for SSD devices and sparse/thinly-provisioned LUNs.

              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

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

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

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

              If set, the execute permission bits of the file will be allowed only if the  exten-
              sion 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  direc-
              tories.  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  overrid-
              ing 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 per-
              mission 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 inacces-

              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 char-
              acters. 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  CON-
              FIG_NLS_UTF8 to be set in the kernel .config file.

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

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

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

              Define  the 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 writable again  by
       remounting it.

Mount options for ncpfs
       Just   like   nfs,   the   ncpfs  implementation  expects  a  binary  argument  (a  struct
       ncp_mount_data) to the mount system call. This argument is constructed by ncpmount(8)  and
       the current version of mount (2.12) does not know anything about ncpfs.

Mount options for nfs and nfs4
       See the options section of the nfs(5) man page (nfs-utils package must be installed).

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

Mount options for ntfs
              Character set to use when returning file names.  Unlike VFAT, NTFS suppresses names
              that contain nonconvertible characters. Deprecated.

              New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

              For 0 (or `no' or `false'), do not use escape sequences for unknown Unicode charac-
              ters.   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  bigen-
              dian 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 compat-
              ible 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 colli-

              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 EHASH-
                     COLLISION 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 filesys-

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

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

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

       nolog  Disable journaling. This will provide slight performance improvements in some situ-
              ations at the cost of losing reiserfs's fast recovery from crashes.  Even with this
              option  turned  on,  reiserfs  still  performs  all journaling operations, save for
              actual writes into its journaling area.  Implementation  of  nolog  is  a  work  in

       notail By  default,  reiserfs  stores small files and `file tails' directly into its tree.
              This confuses some utilities such as LILO(8).  This option is used to disable pack-
              ing 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  spe-
              cial  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  journaling  code.   bar-
              rier=none  disables it, barrier=flush enables it. Write barriers enforce proper on-
              disk ordering of journal commits, 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 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 ker-
              nel  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 auto-
              matic  mount  options.  It can be added later, when the tmpfs is already mounted on
              MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.

Mount options for ubifs
       UBIFS is a flash file system which works on top of UBI volumes. Note  that  atime  is  not
       supported and is always turned off.

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

              ubiY   UBI device number 0, volume number Y

                     UBI device number X, volume with name NAME

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

       The following mount options are available:

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

              Do not bulk-read. This is the default.

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

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

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

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

              Show deleted files in lists.

              Unset strict conformance.

              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

              Override standard anchor location. Default: 256.

              Override the VolumeDesc location. (unused)

              Override the PartitionDesc location. (unused)

              Set the last block of the filesystem.

              Override the fileset block location. (unused)

              Override the root directory location. (unused)

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

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

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

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

              5xbsd  Synonym for ufs2.

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

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

              Set 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  encoun-
                     tered 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.  This option is obsolete.

              First try to make a short name without sequence number, before trying name~num.ext.

       utf8   UTF8  is the filesystem safe 8-bit encoding of Unicode that is used by the console.
              It can be enabled for the filesystem with this  option  or  disabled  with  utf8=0,
              utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets disabled.


              Defines  the  behaviour  for  creation  and display of filenames which fit into 8.3
              characters. If a long name for a file exists, it will always be preferred  display.
              There are four modes: :

              lower  Force  the short name to lower case upon display; store a long name when the
                     short name is not all upper case.

              win95  Force the short name to upper case upon display; store a long name when  the
                     short name is not all upper case.

              winnt  Display  the  shortname  as is; store a long name when the short name is not
                     all lower case or all upper case.

              mixed  Display the short name as is; store a long name when the short name  is  not
                     all upper case. This mode is the default since Linux 2.6.32.

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

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

       listuid=uid and listgid=gid and listmode=mode
              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.  Valid  values  for this option are page size (typically 4KiB) through to
              1GiB, inclusive, in power-of-2 increments.

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

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

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

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

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

              Enable/disable the issuing of commands to let the block device reclaim space  freed
              by  the  filesystem.   This  is useful for SSD devices, thinly provisioned LUNs and
              virtual machine images, but may have a performance impact.

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

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

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

       When ikeep is specified, XFS does not delete empty inode
              clusters  and  keeps  them  around on disk.  When noikeep is specified, empty inode
              clusters are returned to the free space pool.

              When inode32 is specified, it indicates that XFS limits inode creation to locations
              which will not result in inode numbers with more than 32 bits of significance.

              When inode64 is specified, it 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.

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

              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/mod-
              ify/write I/O.  This is typically the page size of the  machine,  as  this  is  the
              granularity of the page cache.

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

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

              The default value is 8 buffers.

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

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

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

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

              Data  allocations will not be aligned at stripe unit boundaries. This is only rele-
              vant to filesystems created with non-zero data alignment parameters (sunit, swidth)
              by mkfs.

              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.  Filesys-
              tems mounted "norecovery" must be mounted read-only or the mount will fail.

       nouuid Don't check for double mounted file systems using the file system  uuid.   This  is
              useful  to mount LVM snapshot volumes, and often used in combination with "norecov-
              ery" for mounting read-only snapshots.

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

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

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

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

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

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

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

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

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

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

       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 and sizelimit , that  are
       really options to losetup(8).  (These options can be used in addition to those specific to
       the filesystem type.)

       Since Linux 2.6.25 is supported auto-destruction of loop devices and then any loop  device
       allocated by mount will be freed by umount 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  command  mount  -a  returns 0 (all success), 32 (all failed) or 64 (some failed, some

       The syntax of external mount helpers is:

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

       where the <type> is filesystem type and -sfnvo options have  same  meaning  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

              overrides the default location of the fstab file

              overrides the default location of the mtab file

              enables debug output

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

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

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

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

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

       The loop option with the offset or sizelimit options used may fail when using  older  ker-
       nels if the mount command can't confirm that the size of the block device has been config-
       ured as requested. This situation can be worked around by using the losetup command  manu-
       ally before calling mount with the configured loop device.

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

       Karel Zak <kzak AT>

       The  mount  command is part of the util-linux package and is available from ftp://ftp.ker-

util-linux                                 January 2012                                  MOUNT(8)

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