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       mount - mount a filesystem


       mount [-lhV]

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

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

       mount [-fnrsvw] [-t vfstype] [-o options] device dir


       All files accessible in a Unix system are arranged in one big tree, the
       file hierarchy, rooted at /.   These  files  can  be  spread  out  over
       several  devices.  The  mount  command  serves to attach the filesystem
       found on some device to the big file tree.  Conversely,  the  umount(8)
       command will detach it again.

       The standard form of the mount command, is

              mount -t type device dir

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

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

              mount -h
                     prints a help message

              mount -V
                     prints a version string

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

       The bind mounts.
              Since Linux 2.4.0 it is possible to remount  part  of  the  file
              hierarchy somewhere else. The call is
                     mount --bind olddir newdir
              or shortoption
                     mount -B olddir newdir
              or fstab entry is:
                     /olddir /newdir none bind

              After  this  call the same contents is accessible in two places.
              One can also remount a single file (on a single file).

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

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

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

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

                     mount --make-shared mountpoint
                     mount --make-slave mountpoint
                     mount --make-private mountpoint
                     mount --make-unbindable mountpoint

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

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

       The device indication.
              Most  devices  are  indicated by a file name (of a block special
              device), like /dev/sda1, but there are other possibilities.  For
              example,  in  the  case  of  an  NFS mount, device may look like
      It is possible to indicate a  block  special
              device using its volume LABEL or UUID (see the -L and -U options

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

       The /etc/fstab, /etc/mtab and /proc/mounts files.
              The file /etc/fstab (see fstab(5)), may contain lines describing
              what devices are usually mounted where, using which options.

              The command

                     mount -a [-t type] [-O optlist]

              (usually given in a bootscript) causes all filesystems mentioned
              in fstab (of the proper type and/or having  or  not  having  the
              proper  options)  to  be  mounted as indicated, except for those
              whose line contains the noauto keyword.  Adding  the  -F  option
              will  make  mount  fork,  so  that  the  filesystems are mounted

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

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

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

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

              Thus, given a line

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

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

                     mount /dev/cdrom


                     mount /cd

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


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

       Command line options available for the mount command:

       -V     Output version.

       -h     Print a help message.

       -v     Verbose mode.

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

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

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

       -f     Causes everything to be done except for the actual system  call;
              if  it’s  not  obvious,  this ‘‘fakes’’ mounting the filesystem.
              This option is  useful  in  conjunction  with  the  -v  flag  to
              determine what the mount command is trying to do. It can also be
              used to add entries for devices that were mounted  earlier  with
              the  -n  option.  The  -f  option  checks for existing record in
              /etc/mtab and fails when the record already exists (with regular
              non-fake mount, this check is done by kernel).

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

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

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

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

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

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

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

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

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

       -t vfstype
              The argument following the -t is used to indicate the filesystem
              type.   The  filesystem  types  which  are  currently  supported
              include: adfs,  affs,  autofs,  cifs,  coda,  coherent,  cramfs,
              debugfs, devpts, efs, ext, ext2, ext3, ext4, hfs, hfsplus, hpfs,
              iso9660, jfs, minix, msdos, ncpfs, nfs, nfs4, ntfs, proc,  qnx4,
              ramfs,  reiserfs,  romfs,  smbfs, sysv, tmpfs, udf, ufs, umsdos,
              usbfs, vfat, xenix, xfs, xiafs.  Note that  coherent,  sysv  and
              xenix are equivalent and that xenix and coherent will be removed
              at some point in the future — use  sysv  instead.  Since  kernel
              version  2.1.21  the  types  ext and xiafs do not exist anymore.
              Earlier, usbfs was known as usbdevfs.  Note, the  real  list  of
              all supported filesystems depends on your kernel.

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

              If  no  -t  option  is  given, or if the auto type is specified,
              mount will try to guess the desired type.  Mount uses the  blkid
              or  volume_id  library for guessing the filesystem type; if that
              does not turn up anything that looks familiar, mount will try to
              read  the  file  /etc/filesystems,  or,  if that does not exist,
              /proc/filesystems.  All of the  filesystem  types  listed  there
              will  be tried, except for those that are labeled "nodev" (e.g.,
              devpts, proc and nfs).  If /etc/filesystems ends in a line  with
              a single * only, mount will read /proc/filesystems afterwards.

              The auto type may be useful for user-mounted floppies.  Creating
              a file /etc/filesystems can be useful to change the probe  order
              (e.g.,  to  try vfat before msdos or ext3 before ext2) or if you
              use a kernel module autoloader.  Warning:  the  probing  uses  a
              heuristic  (the  presence  of  appropriate  ‘magic’),  and could
              recognize the wrong filesystem type, possibly with  catastrophic
              consequences.  If  your  data  is  valuable,  don’t ask mount to

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

              For example, the command:
                     mount -a -t nomsdos,ext
              mounts all filesystems except those of type msdos and ext.

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

                     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

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

                     mount -a -t ext2 -O _netdev

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

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

              For  more  details, see FILESYSTEM INDEPENDENT MOUNT OPTIONS and

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

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

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


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

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

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

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

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

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

       auto   Can be mounted with the -a option.

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

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

              A   commonly   used    option    for    removable    media    is

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

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

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

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

              For more details, see selinux(8)

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

       dev    Interpret character or block special devices on the  filesystem.

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

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

              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 group,dev,suid).

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

              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

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

              Do  not  use  relatime  feature.  See also the strictatime mount

              Allows to explicitly requesting full atime updates.  This  makes
              it  possible  for  kernel to defaults to relatime or noatime but
              still allow userspace to override it. For more details about the
              default system mount options see /proc/mounts.

              Use  the  kernel’s  default  behaviour  for  inode  access  time

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

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

       owner  Allow  an ordinary (i.e., non-root) user to mount the filesystem
              if he is the owner of  the  device.   This  option  implies  the
              options  nosuid  and  nodev  (unless  overridden  by  subsequent
              options, as in the option line owner,dev,suid).

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

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

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

              After this call all old mount options are replaced and arbitrary
              stuff  from  fstab  is ignored, except the loop= option which is
              internally generated and maintained by the mount command.

              mount -o remount,rw  /dir

              After this call mount reads fstab (or  mtab)  and  merges  these
              options with options from command line ( -o ).

       ro     Mount the filesystem read-only.

       rw     Mount the filesystem read-write.

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

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

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

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


       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

Mount options for adfs

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

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

Mount options for affs

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

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

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

              Do  not  allow  any  changes  to  the  protection  bits  on  the

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

              Print an informational message for each successful mount.

              Prefix used before volume name, when following a link.

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

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

              Give explicitly the location of the root block.

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

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

Mount options for cifs

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

Mount options for coherent


Mount options for debugfs

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

Mount options for devpts

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

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

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

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

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

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

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


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

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

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

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

Mount options for ext

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

Mount options for ext2

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

              Support POSIX Access Control Lists (or not).

              Set  the  behaviour  for  the  statfs  system  call. The minixdf
              behaviour is to return in the f_blocks field the total number of
              blocks  of  the  filesystem, while the bsddf behaviour (which is
              the default) is to subtract the overhead blocks used by the ext2
              filesystem and not available for file storage. Thus

              % mount /k -o minixdf; df /k; umount /k
              Filesystem   1024-blocks  Used Available Capacity Mounted on
              /dev/sda6      2630655   86954  2412169      3%   /k
              % mount /k -o bsddf; df /k; umount /k
              Filesystem   1024-blocks  Used Available Capacity Mounted on
              /dev/sda6      2543714      13  2412169      0%   /k

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

              No checking is done at mount time. This is the default. This  is
              fast.   It  is wise to invoke e2fsck(8) every now and then, e.g.
              at boot time.

       debug  Print debugging info upon each (re)mount.

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

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

              These options are accepted but ignored.

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

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

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

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

       sb=n   Instead  of  block  1,  use block n as superblock. This could be
              useful when the filesystem has been damaged.   (Earlier,  copies
              of  the  superblock would be made every 8192 blocks: in block 1,
              8193, 16385, ... (and one got  thousands  of  copies  on  a  big
              filesystem).  Since  version  1.08,  mke2fs  has  a  -s  (sparse
              superblock) option to reduce the number of  backup  superblocks,
              and  since  version 1.15 this is the default. Note that this may
              mean that ext2 filesystems created by a recent mke2fs cannot  be
              mounted  r/w  under Linux 2.0.*.)  The block number here uses 1k
              units. Thus, if you  want  to  use  logical  block  32768  on  a
              filesystem with 4k blocks, use "sb=131072".

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

Mount options for ext3

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

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

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

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

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

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

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

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

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

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

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

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

Mount options for ext4

       The  ext4  filesystem  is  an  an advanced level of the ext3 filesystem
       which  incorporates  scalability  and  reliability   enhancements   for
       supporting large filesystem.

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

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

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

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

       barrier=0 / barrier=1 / barrier / nobarrier
              This enables/disables the use of write barriers in the jbd code.
              barrier=0 disables, barrier=1 enables.  This also requires an IO
              stack which can support barriers, and if jbd gets an error on  a
              barrier  write,  it  will  disable  again with a warning.  Write
              barriers enforce proper on-disk  ordering  of  journal  commits,
              making   volatile  disk  write  caches  safe  to  use,  at  some
              performance penalty.  If your disks are  battery-backed  in  one
              way   or   another,   disabling   barriers  may  safely  improve
              performance.  The mount options "barrier"  and  "nobarrier"  can
              also be used to enable or disable barriers, for consistency with
              other ext4 mount options.

              The ext4 filesystem enables write barriers by default.

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

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

              Deferring block allocation until write-out time.

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

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

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

              The  I/O  priority (from 0 to 7, where 0 is the highest priorty)
              which should be used for I/O operations submitted by  kjournald2
              during  a  commit  operation.   This  defaults  to 3, which is a
              slightly higher priority than the default I/O priority.

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

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

              or worse yet

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

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

Mount options for fat

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

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

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

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

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

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

              This option controls the permission check of mtime/atime.

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

              2      Other users can change timestamp.

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

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

              Three different levels of pickyness can be chosen:

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

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

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

              Sets the codepage for converting to shortname characters on  FAT
              and VFAT filesystems. By default, codepage 437 is used.

              The fat filesystem can perform CRLF<-->NL (MS-DOS text format to
              UNIX text  format)  conversion  in  the  kernel.  The  following
              conversion modes are available:

              binary no translation is performed.  This is the default.

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

              auto   CRLF<-->NL  translation  is  performed  on all files that
                     don’t have a "well-known binary" extension. The  list  of
                     known  extensions  can  be  found  at  the  beginning  of
                     fs/fat/misc.c (as of 2.0, the list  is:  exe,  com,  bin,
                     app,  sys,  drv,  ovl, ovr, obj, lib, dll, pif, arc, zip,
                     lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz,  gz,  tgz,
                     deb,  gif,  bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl,

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

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

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

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

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

              Specify a 12, 16 or 32 bit fat.  This  overrides  the  automatic
              FAT type detection routine.  Use with caution!

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

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

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

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

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

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

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

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

Mount options for hfs

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

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

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

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

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

       quiet  Don’t complain about invalid mount options.

Mount options for hpfs

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

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

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

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

              Do not abort mounting when certain consistency checks fail.

Mount options for iso9660

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

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

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

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

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

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

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

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

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

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

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

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

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

              Select number of session on multisession CD. (Since 2.3.4.)

              Session begins from sector xxx. (Since 2.3.4.)

       The following options are the same as for vfat and specifying them only
       makes  sense  when  using  discs  encoded  using   Microsoft’s   Joliet

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

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

Mount options for jfs

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

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

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

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

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

              These options are accepted but ignored.

Mount options for minix


Mount options for msdos

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

Mount options for ncpfs

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

Mount options for nfs and nfs4

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

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

Mount options for ntfs

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

              New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

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

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

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

Mount options for proc

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

Mount options for ramfs

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

Mount options for reiserfs

       Reiserfs is a journaling filesystem.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Mount options for romfs


Mount options for smbfs

       Just  like  nfs,  the smbfs implementation expects a binary argument (a
       struct smb_mount_data) to the  mount  system  call.  This  argument  is
       constructed by smbmount(8) and the current version of mount (2.12) does
       not know anything about smbfs.

Mount options for sysv


Mount options for tmpfs

              Override default maximum size of the filesystem.   The  size  is
              given  in bytes, and rounded up to entire pages.  The default is
              half of the memory. The size parameter also accepts a  suffix  %
              to limit this tmpfs instance to that percentage of your physical
              RAM: the default, when neither size nor nr_blocks is  specified,
              is size=50%

              The same as size, but in blocks of PAGE_CACHE_SIZE

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

       The tmpfs mount options for sizing ( size,  nr_blocks,  and  nr_inodes)
       accept  a  suffix k, m or g for Ki, Mi, Gi (binary kilo, mega and giga)
       and can be changed on remount.

       mode=  Set initial permissions of the root directory.

       uid=   The user id.

       gid=   The group id.

              Set the NUMA memory allocation policy  for  all  files  in  that
              instance  (if  the kernel CONFIG_NUMA is enabled) - which can be
              adjusted on the fly via ’mount -o remount ...’

                     prefers to allocate memory from the local node

                     prefers to allocate memory from the given Node

                     allocates memory only from nodes in NodeList

                     prefers to allocate from each node in turn

                     allocates from each node of NodeList in turn.

              The NodeList format is a comma-separated list of decimal numbers
              and  ranges, a range being two hyphen-separated decimal numbers,
              the smallest  and  largest  node  numbers  in  the  range.   For
              example, mpol=bind:0-3,5,7,9-15

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

Mount options for udf

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

              Show deleted files in lists.

              Unset strict conformance.

              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

              Override standard anchor location. Default: 256.

              Override the VolumeDesc location. (unused)

              Override the PartitionDesc location. (unused)

              Set the last block of the filesystem.

              Override the fileset block location. (unused)

              Override the root directory location. (unused)

Mount options for ufs

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

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

              44bsd  For    filesystems   created   by   a   BSD-like   system

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

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

              Set behaviour on error:

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

                     These mount options don’t do anything at present; when an
                     error is encountered only a console message is printed.

Mount options for umsdos

       See mount options for msdos.  The dotsOK option is explicitly killed by

Mount options for vfat

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

              Translate  unhandled  Unicode  characters  to  special   escaped
              sequences.   This lets you backup and restore filenames that are
              created with any Unicode characters. Without this option, a  ’?’
              is used when no translation is possible. The escape character is
              ’:’ because it is otherwise illegal on the vfat filesystem.  The
              escape   sequence  that  gets  used,  where  u  is  the  unicode
              character, is: ’:’, (u & 0x3f), ((u>>6) & 0x3f), (u>>12).

       posix  Allow two files with names that only differ in case.

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

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


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

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

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

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

              mixed  Display the short name as is; store a long name when  the
                     short name is not all upper case.

Mount options for usbfs

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

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

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

Mount options for xenix


Mount options for xfs

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

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

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

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

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

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

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

              Indicates  that  XFS is allowed to create inodes at any location
              in the filesystem, including those which will  result  in  inode
              numbers  occupying  more  than 32 bits of significance.  This is
              provided for backwards compatibility, but  causes  problems  for
              backup applications that cannot handle large inode numbers.

              If   nolargeio   is  specified,  the  optimal  I/O  reported  in
              st_blksize by stat(2) will be as small as possible to allow user
              applications  to  avoid  inefficient  read/modify/write I/O.  If
              largeio is specified, a filesystem that has a  swidth  specified
              will  return  the  swidth value (in bytes) in st_blksize. If the
              filesystem does not have a swidth specified but does specify  an
              allocsize  then  allocsize  (in bytes) will be returned instead.
              If neither of these two options are specified,  then  filesystem
              will behave as if nolargeio was specified.

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

              Set the  size  of  each  in-memory  log  buffer.   Size  may  be
              specified  in  bytes,  or in kilobytes with a "k" suffix.  Valid
              sizes for version 1 and version 2 logs are 16384 (16k) and 32768
              (32k).  Valid sizes for version 2 logs also include 65536 (64k),
              131072 (128k) and 262144 (256k).  The default value for machines
              with  more  than  32MiB  of  memory is 32768, machines with less
              memory use 16384 by default.

       logdev=device and rtdev=device
              Use an external log (metadata journal) and/or real-time  device.
              An  XFS  filesystem has up to three parts: a data section, a log
              section, and a real-time  section.   The  real-time  section  is
              optional,  and  the  log  section  can be separate from the data
              section or contained within it.  Refer to xfs(5).

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

              Data allocations will not be aligned at stripe unit  boundaries.

              Access timestamps are not updated when a file is read.

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

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

              Make  O_SYNC writes implement true O_SYNC.  WITHOUT this option,
              Linux XFS behaves as if an osyncisdsync option  is  used,  which
              will make writes to files opened with the O_SYNC flag set behave
              as if the O_DSYNC flag had been used instead.  This  can  result
              in better performance without compromising data safety.  However
              if this option is not in effect, timestamp updates  from  O_SYNC
              writes  can be lost if the system crashes.  If timestamp updates
              are critical, use the osyncisosync option.

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

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

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

       sunit=value and swidth=value
              Used to specify the stripe unit and width for a RAID device or a
              stripe volume.  value must be specified in 512-byte block units.
              If this option is not specified and the filesystem was made on a
              stripe volume or the stripe width or unit were specified for the
              RAID  device  at  mkfs  time,  then  the  mount system call will
              restore the value from the superblock.  For filesystems that are
              made  directly  on  RAID  devices,  these options can be used to
              override the information in the  superblock  if  the  underlying
              disk  layout changes after the filesystem has been created.  The
              swidth  option  is  required  if  the  sunit  option  has   been
              specified, and must be a multiple of the sunit value.

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

Mount options for xiafs

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


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

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

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

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

       If the mount requires a passphrase, you will be prompted for one unless
       you specify a file descriptor to read from instead with the -p  command
       line option, or specify a file name with cleartextkey mount option.  If
       no explicit loop device is mentioned (but just an option ‘-o  loop’  is
       given),  then  mount  will  try to find some unused loop device and use

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

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


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

       0      success

       1      incorrect invocation or permissions

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

       4      internal mount bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded


       The syntax of external mount helpers is:

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

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


       /etc/fstab        filesystem table

       /etc/mtab         table of mounted filesystems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try


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


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

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

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

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

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

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


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


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