Provided by: mount_2.20.1-5.1ubuntu20.9_amd64 bug


       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.

       If only directory or device is given, for example:

              mount /dir

       then  mount  looks  for  a mountpoint and if not found then for a device in the /etc/fstab

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

              mount -h
                     prints a help message

              mount -V
                     prints a version string

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

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

              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 portable. The mount(8) command internally uses udev  symlinks,
              so  the  use  symlinks  in /etc/fstab has no advantage over LABEL=/UUID=.  For more
              details see libblkid(3).

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

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

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

              The command

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

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

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

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

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

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

              Thus, given a line

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

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

                     mount /dev/cdrom


                     mount /cd

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

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

              After this call the same contents is  accessible  in  two  places.   One  can  also
              remount  a single file (on a single file). It's also possible to use the bind mount
              to create a mountpoint from a regular directory, for example:

                     mount --bind foo foo

              The bind mount call attaches only (part  of)  a  single  filesystem,  not  possible
              submounts. The entire file hierarchy including submounts is attached a second place

                     mount --rbind olddir newdir

              or shortoption

                     mount -R olddir newdir

              Note that the filesystem mount options  will  remain  the  same  as  those  on  the
              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

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

              Note  that  behavior  of  the  remount operation depends on the /etc/mtab file. The
              first command stores the 'bind' flag to the /etc/mtab file and the  second  command
              reads  the  flag from the file.  If you have a system without the /etc/mtab file or
              if you explicitly define source and target for the remount command  (then  mount(8)
              does  not  read  /etc/mtab),  then  you  have  to use bind flag (or option) for the
              remount command too. For example:

                     mount --bind olddir newdir
                     mount -o remount,ro,bind olddir 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.   Note  that  the
              olddir has to be a mountpoint.

       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 be cloned through a bind operation.  Detailed  semantics
              is  documented  in  Documentation/filesystems/sharedsubtree.txt  file in the kernel
              source tree.

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

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

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


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

       Command line options available for the mount command:

       -V, --version
              Output version.

       -h, --help
              Print a help message.

       -v, --verbose
              Verbose mode.

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

       -F, --fork
              (Used in conjunction with -a.)  Fork off  a  new  incarnation  of  mount  for  each
              device.   This  will do the mounts on different devices or different NFS servers in
              parallel.  This has the advantage that it  is  faster;  also  NFS  timeouts  go  in
              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 determine what the mount command is trying  to  do.
              It  can  also be used to add entries for devices that were mounted earlier with the
              -n option. The -f option checks for existing record in /etc/mtab and fails when the
              record already exists (with regular non-fake mount, this check is done by kernel).

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

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

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

              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 kernel.

              The programs mount and umount support filesystem subtypes.  The subtype is  defined
              by  '.subtype'  suffix.  For example  'fuse.sshfs'. It's recommended to use subtype
              notation  rather  than  add  any  prefix  to  the   mount   source   (for   example
              '' is depreacated).

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

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

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

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

                     mount -a -t nomsdos,ext

              mounts all filesystems except those of type msdos and ext.

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

                     mount -a -O no_netdev

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

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

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

                     mount -a -t ext2 -O _netdev

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

       -o, --options opts
              Options are specified with a -o flag  followed  by  a  comma  separated  string  of
              options. For example:

                     mount LABEL=mydisk -o noatime,nouser

              MOUNT OPTIONS sections.

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

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

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


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

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

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

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

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

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

       auto   Can be mounted with the -a option.

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

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

              A      commonly      used      option      for       removable       media       is

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

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

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

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

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

              For more details, see selinux(8)

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

       dev    Interpret character or block special devices on the filesystem.

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

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

              Do not update directory inode access times on this filesystem.

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

       exec   Permit execution of binaries.

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

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

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

              Specifies the key size to use for an encryption algorithm. Used in conjunction with
              the loop and encryption options.

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

              Do not increment the i_version inode field.

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

       nomand Do not allow mandatory locks on this filesystem.

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

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

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

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

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

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

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

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

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

       silent Turn on the silent flag.

       loud   Turn off the silent flag.

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

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

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

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

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

              mount -o remount,rw  /dir

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

       ro     Mount the filesystem read-only.

       rw     Mount the filesystem read-write.

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

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

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

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


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

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

Mount options for adfs

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

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

Mount options for affs

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

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

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

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

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

              Print an informational message for each successful mount.

              Prefix used before volume name, when following a link.

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

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

              Give explicitly the location of the root block.

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

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

Mount options for cifs

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

Mount options for coherent


Mount options for debugfs

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

Mount options for devpts

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

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

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

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

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

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

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


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

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

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

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

Mount options for ext

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

Mount options for ext2

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

              Support POSIX Access Control Lists (or not).

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

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

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

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

       debug  Print debugging info upon each (re)mount.

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

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

              These options are accepted but ignored.

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

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

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

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

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

Mount options for ext3

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

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

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

              When the external journal device's major/minor numbers have  changed,  this  option
              allows  the  user  to  specify  the  new  journal  location.  The journal device is
              identified through its new major/minor numbers encoded in devnum.

              Don't load the journal on mounting.  Note that if the filesystem was not  unmounted
              cleanly,  skipping  the  journal  replay  will  lead  to  the filesystem containing
              inconsistencies that can lead to any number of problems.

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

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

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

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

       barrier=0 / barrier=1
              This enables/disables barriers.   barrier=0  disables  it,  barrier=1  enables  it.
              Write  barriers enforce proper on-disk ordering of journal commits, making volatile
              disk write caches safe to use, at some performance penalty.   The  ext3  filesystem
              does  not enable write barriers by default.  Be sure to enable barriers unless your
              disks are battery-backed  one  way  or  another.   Otherwise  you  risk  filesystem
              corruption in case of power failure.

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

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

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

Mount options for ext4

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

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

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

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

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

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

              The ext4 filesystem enables write barriers by default.

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

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

              Deferring block allocation until write-out time.

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

              Maximum amount of time ext4 should wait for additional filesystem operations to  be
              batch  together  with  a  synchronous  write  operation.  Since a synchronous write
              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 transaction
              has been running is less than the commit time,  ext4  will  try  sleeping  for  the
              commit  time  to see if other operations will join the transaction. The commit time
              is  capped  by  the  max_batch_time,  which  defaults  to  15000us   (15ms).   This
              optimization can be turned off entirely by setting max_batch_time to 0.

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

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

       abort  Simulate the effects of calling  ext4_abort()  for  debugging  purposes.   This  is
              normally used while remounting a filesystem which is already mounted.

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

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

              or worse yet

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

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

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

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

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

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

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

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

Mount options for fat

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

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

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

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

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

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

              This option controls the permission check of mtime/atime.

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

              2      Other users can change timestamp.

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

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

              Three different levels of pickyness can be chosen:

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

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

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

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

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

              binary no translation is performed.  This is the default.

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

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

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

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

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

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

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

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

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

       tz=UTC This  option  disables  the conversion of timestamps between local time (as used by
              Windows on FAT) and UTC (which Linux uses internally).  This is 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

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

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

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

       quiet  Don't complain about invalid mount options.

Mount options for hpfs

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

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

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

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

              Do not abort mounting when certain consistency checks fail.

Mount options for iso9660

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

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

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

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

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

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

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

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

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

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

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

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

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

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

              Session begins from sector xxx. (Since 2.3.4.)

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

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

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

Mount options for jfs

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

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

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

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

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

              These options are accepted but ignored.

Mount options for minix


Mount options for msdos

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

Mount options for ncpfs

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

Mount options for nfs and nfs4

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

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

Mount options for ntfs

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

              New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

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

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

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

Mount options for proc

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

Mount options for ramfs

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

Mount options for reiserfs

       Reiserfs is a journaling filesystem.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Mount options for romfs


Mount options for squashfs


Mount options for smbfs

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

Mount options for sysv


Mount options for tmpfs

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

              The same as size, but in blocks of PAGE_CACHE_SIZE

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

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

       mode=  Set initial permissions of the root directory.

       uid=   The user id.

       gid=   The group id.

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

                     prefers to allocate memory from the local node

                     prefers to allocate memory from the given Node

                     allocates memory only from nodes in NodeList

                     prefers to allocate from each node in turn

                     allocates from each node of NodeList in turn.

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

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

Mount options for 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 (NetBSD,FreeBSD,OpenBSD).

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

              5xbsd  Synonym for ufs2.

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

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

              Set behaviour on error:

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

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

Mount options for umsdos

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

Mount options for vfat

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

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

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

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

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


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

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

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

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

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

Mount options for usbfs

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

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

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

Mount options for xenix


Mount options for xfs

              Sets the buffered I/O end-of-file preallocation size when doing delayed  allocation
              writeout  (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 enabled) 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 any recent kernel.

              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 any recent kernel is

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

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

              Data allocations will not be aligned at stripe unit boundaries.

              Access timestamps are not updated when a file is read.

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

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

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

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

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

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

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

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

Mount options for xiafs

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


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

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

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

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

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

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

              mount /tmp/disk.img /mnt

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

       This type  of  mount  knows  about  four  options,  namely  loop,  offset,  sizelimit  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.)

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

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


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

       0      success

       1      incorrect invocation or permissions

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

       4      internal mount bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded


       The syntax of external mount helpers is:

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

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


       /etc/fstab        filesystem table

       /etc/mtab         table of mounted filesystems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try


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


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

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

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

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

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

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


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


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