*BASH User Commands Ubuntu 10.04.4 LTS Server coreutils
MOUNT(8)                   Linux Programmer's Manual                  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  sev-
       eral  devices.  The mount command serves to attach the filesystem found
       on some device to the big file tree. Conversely, the umount(8)  command
       will detach it again.

       The standard form of the mount command, is

              mount -t type device dir

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

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

              mount -h
                     prints a help message

              mount -V
                     prints a version string

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

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

              The  recommended  setup  is  to use LABEL=<label> or UUID=<uuid>
              tags rather than /dev/disk/by-{label,uuid} udev symlinks in  the
              /etc/fstab  file.  The tags are more readable, robust and porta-
              ble. The mount(8) command internally uses udev symlinks, so  use
              the  symlinks  in /etc/fstab is not advantage over LABEL=/UUID=.
              For more details see libblkid(3).

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

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

              The command

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

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

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

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

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

                     mount /dev/foo /dir

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

                     mount device|dir -o <options>

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

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

       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).

              This call attaches only (part of) a single filesystem, not  pos-
              sible  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  mount
              options  can be changed by a separate remount command, for exam-

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

       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.

       The shared subtrees operations.
              Since  Linux  2.6.15 it is possible to mark a mount and its sub-
              mounts as shared, private, slave or unbindable. A  shared  mount
              provides  ability  to  create  mirrors  of  that mount such that
              mounts and umounts within any of the mirrors  propagate  to  the
              other  mirror.  A slave mount receives propagation from its mas-
              ter, but any not vice-versa.  A private mount carries no  propa-
              gation  abilities.   A unbindable mount is a private mount which
              cannot 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  full set of mount options used by an invocation of mount is deter-
       mined by first extracting the mount options for the filesystem from the
       fstab  table,  then  applying any options specified by the -o argument,
       and finally applying a -r or -w option, when present.

       Command line options available for the mount command:

       -V, --version
              Output version.

       -h, --help
              Print a help message.

       -v, --verbose
              Verbose mode.

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

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

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

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

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

              Don't  canonicalize  paths.  The mount command canonicalizes all
              paths (from command line  or  fstab)  and  stores  canonicalized
              paths  to  the  /etc/mtab file. This option can be used together
              with the -f flag for already canonicalized absolut paths.

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

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

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

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

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

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

       -U uuid
              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, --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,  reiserfs,  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 ker-

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

              If no -t option is given, or if  the  auto  type  is  specified,
              mount  will try to guess the desired type.  Mount uses the blkid
              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  rec-
              ognize  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, --test-opts opts
              Used in conjunction with -a, to limit the set of filesystems  to
              which  the -a is applied.  Like -t in this regard except that it
              is useless except in the context of -a.  For example,  the  com-

                     mount -a -O no_netdev

              mounts  all filesystems except those which have the option _net-
              dev 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 opts
              Options  are  specified with a -o flag followed by a comma sepa-
              rated string of options. For example:

                     mount LABEL=mydisk -o noatime,nouser

              For more details, see FILESYSTEM INDEPENDENT MOUNT  OPTIONS  and

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

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

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

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

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

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

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

       atime  Update  inode access time for each access. See also the stricta-
              time 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  rootcon-
              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=sys-

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

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

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

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

              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  syn-
              chronously.   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).

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

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

              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

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

              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 com-
              monly used to change the mount flags  for  a  filesystem,  espe-
              cially  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 com-
              mand doesn't read fstab (or mtab) only when a device and dir are
              fully specified.

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

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

              mount -o remount,rw  /dir

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

       ro     Mount the filesystem read-only.

       rw     Mount the filesystem read-write.

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

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

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

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

       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  Documenta-

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,  respec-
              tively).    See    also    /usr/src/linux/Documentation/filesys-

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

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

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

              Do  not allow any changes to the protection bits on the filesys-

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

              Print an informational message for each successful mount.

              Prefix used before volume name, when following a link.

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

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

              Give explicitly the location of the root block.

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

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

Mount options for cifs
       See  the  options  section of the mount.cifs(8) man page (smbfs 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 CON-
              FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel  configu-

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


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

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

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

              This  option is only implemented in linux kernel versions start-
              ing with 2.6.29. Further this  option  is  valid  only  if  CON-
              FIG_DEVPTS_MULTIPLE_INSTANCES  is enabled in the kernel configu-

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 behav-
              iour is to return in the f_blocks  field  the  total  number  of
              blocks  of  the  filesystem, while the bsddf behaviour (which is
              the default) is to subtract the overhead blocks used by the ext2
              filesystem and not available for file storage. Thus

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

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

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

       debug  Print debugging info upon each (re)mount.

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

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

              These options are accepted but ignored.

       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 avail-
              able 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

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

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

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

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

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

       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,  bar-
              rier=1 enables it.  Write barriers enforce proper on-disk order-
              ing of journal commits, making volatile disk write  caches  safe
              to  use,  at some performance penalty.  The ext3 filesystem does
              not enable write barriers by default.  Be sure to enable  barri-
              ers  unless  your  disks  are battery-backed one way or another.
              Otherwise you risk filesystem corruption in case of power  fail-

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

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

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

Mount options for ext4
       The ext4 filesystem is an an advanced  level  of  the  ext3  filesystem
       which  incorporates  scalability  and reliability enhancements for sup-
       porting 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 cor-
              ruption in the kernel.  It is a compatible change  and  will  be
              ignored by older kernels.

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

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

       barrier=0 / barrier=1 / barrier / nobarrier
              This enables/disables the use of write barriers in the jbd code.
              barrier=0 disables, barrier=1 enables.  This also requires an IO
              stack  which can support barriers, and if jbd gets an error on a
              barrier write, it will disable again with a warning.  Write bar-
              riers enforce proper on-disk ordering of journal commits, making
              volatile disk write caches safe  to  use,  at  some  performance
              penalty.   If  your  disks  are  battery-backed  in  one  way or
              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 filesys-
              tem operations to be batch together  with  a  synchronous  write
              operation. Since a synchronous write operation is going to force
              a commit and then a wait for the I/O complete, it  doesn't  cost
              much,  and  can  be  a  huge throughput win, we wait for a small
              amount of time to see if any other transactions can piggyback on
              the  synchronous  write. The algorithm used is designed to auto-
              matically tune for the speed  of  the  disk,  by  measuring  the
              amount of time (on average) that it takes to finish committing a
              transaction. Call this time the "commit time".  If the time that
              the  transactoin  has been running is less than the commit time,
              ext4 will try sleeping for the commit time to see if other oper-
              ations  will  join the transaction. The commit time is capped by
              the max_batch_time, which defaults to 15000us (15ms). This opti-
              mization can be turned off entirely by setting max_batch_time to

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

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

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

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

              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 verylong.foo), leading and  embedded  spaces  are
                     accepted in each name part (name and extension).

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

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

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

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

              binary no translation is performed.  This is the default.

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

              auto   CRLF<-->NL translation is performed  on  all  files  that
                     don't  have  a "well-known binary" extension. The list of
                     known  extensions  can  be  found  at  the  beginning  of
                     fs/fat/misc.c  (as  of  2.0,  the list is: exe, com, bin,
                     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 con-
              version.  Several people have had  their  data  ruined  by  this
              translation. Beware!

              For filesystems mounted in binary mode, a conversion tool (from-
              dos/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 mod-
              ule loading.  This option is obsolete.

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

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

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

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

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

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

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

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

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

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

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

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 any-
              thing but a CDROM as underlying device.

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

       quiet  Don't complain about invalid mount options.

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

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

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

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

              Do not abort mounting when certain consistency checks fail.

Mount options for iso9660
       ISO 9660 is a standard describing a filesystem structure to be used  on
       CD-ROMs.  (This filesystem type is also seen on some DVDs. See also the
       udf filesystem.)

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

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

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

              Disable the use of Microsoft Joliet extensions, even  if  avail-
              able. 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  dan-
              gerous, possibly leading to silent data corruption.)

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

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

              Session begins from sector xxx. (Since 2.3.4.)

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

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

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

Mount options for jfs
              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 key-
              word with no value will grow the volume to the full size of  the

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

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

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

              These options are accepted but ignored.

Mount options for minix

Mount options for msdos
       See  mount  options for fat.  If the msdos filesystem detects an incon-
       sistency, it reports an error and sets the file system  read-only.  The
       filesystem can be made 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  con-
       structed  by  ncpmount(8)  and the current version of mount (2.12) does
       not know anything about ncpfs.

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

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

Mount options for ntfs
              Character set to use when returning file  names.   Unlike  VFAT,
              NTFS  suppresses  names  that  contain 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 pre-
                     serves  locality,  mapping  lexicographically  close file
                     names to close hash values.  This option  should  not  be
                     used, as it causes a high probability of hash collisions.

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

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

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

              Tunes the block allocator. This may provide performance improve-
              ments in some situations.

              Tunes the block allocator. This may provide performance improve-
              ments in some situations.

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

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

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

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

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

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

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

       barrier=none / barrier=flush
              This  enables/disables the use of write barriers in the journal-
              ing code.  barrier=none disables it, barrier=flush  enables  it.
              Write  barriers  enforce proper on-disk ordering of journal com-
              mits, making volatile disk write caches safe  to  use,  at  some
              performance  penalty.  The  reiserfs  filesystem does not enable
              write barriers by default. Be sure  to  enable  barriers  unless
              your  disks are battery-backed one way or another. Otherwise you
              risk filesystem corruption in case of power failure.

Mount options for romfs

Mount options for squashfs

Mount options for smbfs
       Just like nfs, the smbfs implementation expects a  binary  argument  (a
       struct  smb_mount_data) to the mount system call. This argument is con-
       structed 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 exam-
              ple, mpol=bind:0-3,5,7,9-15

              Note that trying to mount a tmpfs with an mpol option will  fail
              if  the  running  kernel does not support NUMA; and will fail if
              its nodelist specifies a node which is not online.  If your sys-
              tem  relies  on  that tmpfs being mounted, but from time to time
              runs a kernel built without  NUMA  capability  (perhaps  a  safe
              recovery  kernel), or with fewer nodes online, then it is advis-
              able to omit the mpol option from automatic mount  options.   It
              can  be added later, when the tmpfs is already mounted on Mount-
              Point, 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 information. This option only
              affects reading, not writing. CRC-32 is always  calculated  when
              writing the data.

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

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

       gid=   Set the default group.

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

       uid=   Set the default user.

       unhide Show otherwise hidden files.

              Show deleted files in lists.

              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  charac-
              ter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).

       posix  Allow  two  files  with  names  that  only differ in case.  This
              option is obsolete.

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

       utf8   UTF8  is  the  filesystem safe 8-bit encoding of Unicode that is
              used by the console. It can be 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 val-
              ues for this option are page size (typically  4KiB)  through  to
              1GiB, inclusive, in power-of-2 increments.

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

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

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

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

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

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

              Indicates  that  XFS is allowed to create inodes at any location
              in the filesystem, including those which will  result  in  inode
              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_blk-
              size 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 filesys-
              tems 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  speci-
              fied  in  bytes, or in kilobytes with a "k" suffix.  Valid sizes
              for version 1 and version 2  logs  are  16384  (16k)  and  32768
              (32k).  Valid sizes for version 2 logs also include 65536 (64k),
              131072 (128k) and 262144 (256k).  The default value for machines
              with more than 32MiB of memory is 32768, machines with less mem-
              ory 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 sec-
              tion or contained within it.  Refer to xfs(5).

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

              Data allocations will not be aligned at stripe unit boundaries.

              Access timestamps are not updated when a file is read.

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

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

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

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

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

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

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

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

       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  inde-
       pendently 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
       from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.

Linux 2.6                         2004-12-16                          MOUNT(8)