MOUNT(8)					       System Administration						  MOUNT(8)



NAME
       mount - mount a filesystem

SYNOPSIS
       mount [-lhV]

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

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

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

DESCRIPTION
       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 file.

       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 possibil‐
	      ities. 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 below).

	      The  recommended	setup  is to use LABEL=<label> or UUID=<uuid> tags rather than /dev/disk/by-{label,uuid} udev sym‐
	      links 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 lib‐
	      blkid(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  argu‐
	      ments 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 be‐
	      haviour 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

	      or

		     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 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 example:

		     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 loca‐
	      tion 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 pri‐
	      vate 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


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

       Command line options available for the mount command:

       -V, --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.

       --no-canonicalize
	      Don't  canonicalize paths. The mount command canonicalizes all paths (from command line or fstab) and stores canoni‐
	      calized 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  exam‐
	      ple   'fuse.sshfs'.  It's  recommended  to  use subtype notation rather than add any prefix to the mount source (for
	      example 'sshfs#example.com' 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 neces‐
	      sary. 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


	      For more details, see FILESYSTEM INDEPENDENT MOUNT OPTIONS and FILESYSTEM SPECIFIC 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.


FILESYSTEM INDEPENDENT MOUNT OPTIONS
       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 option.)

       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.

       noatime
	      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 context.

	      A commonly used option for removable media is context=system_u:object_r:removable_t.

	      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 con‐
	      text 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)


       defaults
	      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.

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

       nodiratime
	      Do not update directory inode access times on this filesystem.

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

       exec   Permit execution of binaries.

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

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

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

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

       noiversion
	      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.

       _netdev
	      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.

       relatime
	      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 appli‐
	      cations 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.

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

       strictatime
	      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.

       nostrictatime
	      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).

       remount
	      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 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 sub‐
	      sequent options, as in the option line user,exec,dev,suid).

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

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


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

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


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

       ownmask=value and othmask=value
	      Set the permission mask for ADFS 'owner' permissions and 'other' permissions, respectively (default: 0700 and  0077,
	      respectively).  See also /usr/src/linux/Documentation/filesystems/adfs.txt.

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 speci‐
	      fied value, the uid and gid of the current process are taken).

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

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

       protect
	      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...

       verbose
	      Print an informational message for each successful mount.

       prefix=string
	      Prefix used before volume name, when following a link.

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

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

       root=value
	      Give explicitly the location of the root block.

       bs=value
	      Give blocksize. Allowed values are 512, 1024, 2048, 4096.

       grpquota|noquota|quota|usrquota
	      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 installed).


Mount options for coherent
       None.


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 /dev/pts/<number>.

       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.

       mode=value
	      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.

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

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

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

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

       ptmxmode=value

	      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  deter‐
       mined by the filesystem superblock. Set them with tune2fs(8).

       acl|noacl
	      Support POSIX Access Control Lists (or not).

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

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

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


       check={none|nocheck}
	      No  checking is done at mount time. This is the default. This is fast.  It is wise to invoke e2fsck(8) every now and
	      then, e.g. at boot time.

       debug  Print debugging info upon each (re)mount.

       errors={continue|remount-ro|panic}
	      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.

       grpquota|noquota|quota|usrquota
	      These options are accepted but ignored.

       nouid32
	      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 cre‐
	      ated 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".

       user_xattr|nouser_xattr
	      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:

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

       journal=inum
	      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.

       journal_dev=devnum
	      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.

       norecovery/noload
	      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.

       data={journal|ordered|writeback}
	      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.

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

	      ordered
		     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.

	      writeback
		     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.

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

       user_xattr
	      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 ext2.

       journal_checksum
	      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.

       journal_async_commit
	      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' internally.

       journal=update
	      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.

       inode_readahead=n
	      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.

       stripe=n
	      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.

       delalloc
	      Deferring block allocation until write-out time.

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

       max_batch_time=usec
	      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  com‐
	      plete,  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 transac‐
	      tion. 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.

       min_batch_time=usec
	      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.

       journal_ioprio=prio
	      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.

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

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

       discard/nodiscard
	      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.

       nouid32
	      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.

       block_validity/noblock_validity
	      This options allows to enables/disables the in-kernel facility for tracking filesystem metadata blocks within inter‐
	      nal  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.

       dioread_lock/dioread_nolock
	      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).

       i_version
	      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 filesystems.)

       blocksize={512|1024|2048}
	      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.)

       umask=value
	      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.

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

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

       allow_utime=value
	      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.

       check=value
	      Three different levels of pickyness can be chosen:

	      r[elaxed]
		     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).

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

	      s[trict]
		     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.)

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

       conv={b[inary]|t[ext]|a[uto]}
	      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.

       cvf_format=module
	      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.

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

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

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

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

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

       showexec
	      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.

       sys_immutable
	      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.

       usefree
	      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 process.

       session=n
	      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 ta‐
	      ble 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.)

       umask=value
	      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.

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

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

       nocheck
	      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 char‐
       acters  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.

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

       check={r[elaxed]|s[trict]}
	      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.)

       map={n[ormal]|o[ff]|a[corn]}
	      For non-Rock Ridge volumes, normal name translation maps upper to lower case ASCII, drops a trailing `;1', and  con‐
	      verts  `;' 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.

       mode=value
	      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.)

       block={512|1024|2048}
	      Set the block size to the indicated value.  (Default: block=1024.)

       conv={a[uto]|b[inary]|m[text]|t[ext]}
	      (Default: conv=binary.)  Since Linux 1.3.54 this option has no effect anymore.  (And non-binary settings used to	be
	      very dangerous, possibly leading to silent data corruption.)

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

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

       sbsector=xxx
	      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  Micro‐
       soft's Joliet extensions.

       iocharset=value
	      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
       iocharset=name
	      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=value
	      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.

       nointegrity
	      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.

       integrity
	      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.

       errors={continue|remount-ro|panic}
	      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.)

       noquota|quota|usrquota|grpquota
	      These options are accepted but ignored.


Mount options for minix
       None.


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

       nls=name
	      New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

       uni_xlate={0|1|2}
	      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.

       posix=[0|1]
	      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.

       hash={rupasov|tea|r5|detect}
	      Choose which hash function reiserfs will use to find files within directories.

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

	      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
		     filesystem.

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

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

       noborder
	      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 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.

       replayonly
	      Replay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by  reiserf‐
	      sck.

       resize=number
	      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 ftp://ftp.namesys.com/pub/reiserfsprogs.

       user_xattr
	      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
       None.


Mount options for squashfs
       None.


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
       None.


Mount options for tmpfs
       size=nbytes
	      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 per‐
	      centage of your physical RAM: the default, when neither size nor nr_blocks is specified, is size=50%

       nr_blocks=
	      The same as size, but in blocks of PAGE_CACHE_SIZE

       nr_inodes=
	      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.

       mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
	      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 ...'

	      default
		     prefers to allocate memory from the local node

	      prefer:Node
		     prefers to allocate memory from the given Node

	      bind:NodeList
		     allocates memory only from nodes in NodeList

	      interleave
		     prefers to allocate from each node in turn

	      interleave:NodeList
		     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 dec‐
	      imal 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

	      ubiX:NAME
		     UBI device number X, volume with name NAME

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

       The following mount options are available:

       bulk_read
	      Enable bulk-read. VFS read-ahead is disabled because it slows down the file system. Bulk-Read is an  internal  opti‐
	      mization.  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.

       no_bulk_read
	      Do not bulk-read. This is the default.

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

       no_chk_data_crc.
	      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.

       compr={none|lzo|zlib}
	      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.

       undelete
	      Show deleted files in lists.

       nostrict
	      Unset strict conformance.

       iocharset
	      Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

       anchor=
	      Override standard anchor location. Default: 256.

       volume=
	      Override the VolumeDesc location. (unused)

       partition=
	      Override the PartitionDesc location. (unused)

       lastblock=
	      Set the last block of the filesystem.

       fileset=
	      Override the fileset block location. (unused)

       rootdir=
	      Override the root directory location. (unused)


Mount options for ufs
       ufstype=value
	      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.

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

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

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


       onerror=value
	      Set behaviour on error:

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

	      [lock|umount|repair]
		     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

       uni_xlate
	      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.

       nonumtail
	      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 dis‐
	      abled.

       shortname={lower|win95|winnt|mixed}

	      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
       None.


Mount options for xfs
       allocsize=size
	      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.

       attr2|noattr2
	      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.

       barrier
	      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.

       ihashsize=value
	      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.

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

       inode64
	      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.

       largeio|nolargeio
	      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.

       logbufs=value
	      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.

       logbsize=value
	      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 32768.

       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 sep‐
	      arate from the data section or contained within it.  Refer to xfs(5).

       mtpt=mountpoint
	      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.

       noalign
	      Data allocations will not be aligned at stripe unit boundaries.

       noatime
	      Access timestamps are not updated when a file is read.

       norecovery
	      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.

       osyncisosync
	      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.

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

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

       pquota|prjquota|pqnoenforce
	      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.

       swalloc
	      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.


THE LOOP DEVICE
       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`.


RETURN CODES
       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


NOTES
       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).


FILES
       /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


SEE ALSO
       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)

BUGS
       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  synchro‐
       nous 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 usu‐
       ally contains more reliable information.)

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

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

AVAILABILITY
       The mount command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.




util-linux						   December 2004						  MOUNT(8)