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mount


SYNOPSIS

       mount [-lhV]

       mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
       mount [-fnrsvw] [-o options [,...]] 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  sev-
       eral  devices. The mount command serves to attach the file system 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 file system 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 file
       system remains mounted, the pathname dir refers to the root of the file
       system on device.

       Three forms of invocation do not actually mount anything:
              mount -h
       prints a help message;
              mount -V
       prints a version string; and just
              mount [-l] [-t type]
       lists  all mounted file systems (of type type).  The option -l adds the
       (ext2, ext3, ext4 and XFS) labels in this listing.  See below.

       Since Linux 2.4.0 it is possible to remount part of the file  hierarchy
       somewhere else. The call is
              mount --bind olddir newdir
       After this call the same contents is accessible in two places.  One can
       also remount a single file (on a single file).

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

       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.

       All attribute changes (remount) to the bind mount will propagate to the
       source  mount. The read-only bind mounts are implemented in since Linux
       2.6.26.

       Since Linux 2.5.1 it is possible to atomically move a mounted  tree  to
       another place. The call is
              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 proc file system 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.)

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

       The  file  /etc/fstab (see fstab(5)), may contain lines describing what
       devices are usually mounted where, using which options.  This  file  is
       used in three ways:

       (i) The command
              mount -a [-t type] [-O optlist]
       (usually  given  in  a bootscript) causes all file systems 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 con-
       tains the noauto keyword. Adding the -F option will make mount fork, so
       that the filesystems are mounted simultaneously.

       (ii)  When  mounting  a  file system mentioned in fstab, it suffices to
       give only the device, or only the mount point.

       (iii) Normally, only the superuser can mount  file  systems.   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 file system 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 filesys-
       tem 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 simi-
       lar 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
       ing  with the loop device will be less convenient, and using the "user"
       option will fail.


OPTIONS

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

       Options available for the mount command:

       -V     Output version.

       -h     Print a help message.

       -v     Verbose mode.

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

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

       -f     Causes  everything to be done except for the actual system call;
              if it's not obvious, this ''fakes'' mounting  the  file  system.
              This  option is useful in conjunction with the -v flag to deter-
              mine what the mount command is trying to do. It can also be used
              to add entries for devices that were mounted earlier with the -n
              option.

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

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

       -n     Mount without writing in /etc/mtab.  This is necessary for exam-
              ple when /etc is on a read-only file system.

       -p 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
              2.1.116) to exist.

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

              For most types all the mount program has to do is issue a simple
              mount(2) system call, and no detailed knowledge of the  filesys-
              tem  type is required.  For a few types however (like nfs, nfs4,
              cifs, smbfs, ncpfs) ad hoc code is necessary.  The  nfs  ad  hoc
              code  is  built  in,  but cifs, smbfs, and ncpfs 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.  If mount was compiled
              with  the  blkid  library, the guessing is done by this library.
              Otherwise, mount guesses itself by probing  the  superblock;  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, nfs, and nfs4).  If /etc/filesystems ends
              in a line with a single * only, mount will  read  /proc/filesys-
              tems afterwards.

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

              More than one type may be specified in a comma  separated  list.
              The list of file system types can be prefixed with no to specify
              the file system types on which no action should be taken.  (This
              can be meaningful with the -a option.)
              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 are specified with a -o flag followed by a  comma  sepa-
              rated  string of options.  Some of these options are only useful
              when they appear in the /etc/fstab file.  The following  options
              apply  to  any  file system that is being mounted (but not every
              file system 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 file system should be done asynchronously.

              atime  Update inode access time for each  access.  This  is  the
                     default.

              auto   Can be mounted with the -a option.

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

              dev    Interpret character or block special devices on the  file
                     system.

              exec   Permit execution of binaries.

              group  Allow an ordinary (i.e., non-root) user to mount the file
                     system 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).

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

              _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).

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

                     2.6.0.)

              nomand Do not allow mandatory locks on this filesystem.

              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.)

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

              owner  Allow an ordinary (i.e., non-root) user to mount the file
                     system  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 file system.   This
                     is  commonly  used  to  change the mount flags for a file
                     system, especially to make a readonly file system  write-
                     able. It does not change device or mount point.

              ro     Mount the file system read-only.

              _rnetdev
                     Like  _netdev,  except  "fsck  -a" checks this filesystem
                     during rc.sysinit.

              rw     Mount the file system read-write.

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

              sync   All  I/O to the file system 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.

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

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

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

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

                     For more details see selinux(8)

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

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


FILESYSTEM SPECIFIC MOUNT OPTIONS

       The following options apply only to certain file systems.  We sort them
       by file system. They all follow the -o flag.

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


Mount options for adfs

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

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

       protect
              Do not allow any changes to the protection bits on the file sys-
              tem.

       usemp  Set  uid  and  gid of the root of the file system 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 utili-
              ties may react to such strings in /etc/fstab.)


Mount options for cifs

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


Mount options for cifs

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


Mount options for coherent

       None.

              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.


Mount options for ext

       None.   Note  that  the  'ext'  file  system 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' file system is the standard Linux file system.  Since Linux
       2.5.46, for most  mount  options  the  default  is  determined  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 file system, while the bsddf behaviour (which is
              the default) is to subtract the overhead blocks used by the ext2
              file system 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 / errors=remount-ro / errors=panic
       grpquota / noquota / quota / usrquota
              These options are accepted but ignored.

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

       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 file system reserves a certain percentage of the avail-
              able space (by default 5%, see mke2fs(8) and tune2fs(8)).  These
              options  determine  who  can use the reserved blocks.  (Roughly:
              whoever has the specified  uid,  or  belongs  to  the  specified
              group.)

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

       user_xattr / nouser_xattr
              Support "user." extended attributes (or not).


Mount options for ext3

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

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

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

                     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 file system after its metadata has been  commit-
                     ted  to the journal.  This is rumoured to be the highest-
                     throughput option.  It guarantees  internal  file  system
                     integrity,  however  it  can  allow old data to appear in
                     files after a crash and journal recovery.

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


Mount options for ext4

       The  'ext4' is an an advanced level of the ext3 filesystem which incor-
       porates scalability and reliability enhancements for  supporting  large
       filesystem.

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

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

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

       journal=update
              Update the ext4 file system's journal to the current format.

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

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

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

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

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

       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.

       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] / conv=t[ext] / conv=a[uto]
              The fat file system 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

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

       cvf_option=option
              Option passed to the CVF module.

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

       fat=12 / fat=16 / fat=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 file-
              names are stored on disk in Unicode format.

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

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


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 any-
              thing but a CDROM as underlying device.

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

       quiet  Don't complain about invalid mount options.
              case=lower.)

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

       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 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 file
       system (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 avail-
              able. Cf. map.

       check=r[elaxed] / check=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 file system the indicated  user  or  group
              id,  possibly overriding the information found in the Rock Ridge
              extensions.  (Default: uid=0,gid=0.)

       map=n[ormal] / map=o[ff] / map=a[corn]
              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.

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

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

       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 Microsoft's Joliet exten-
       sions.

       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  key-
              word  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 pre-
              viously specified in order to restore normal behavior.

       errors=continue / errors=remount-ro / errors=panic
       See mount options for fat.  If the msdos file system detects an  incon-
       sistency,  it  reports an error and sets the file system read-only. The
       file system can be made writeable again by remounting it.


Mount options for ncpfs

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


Mount options for nfs

       Instead  of a textual option string, parsed by the kernel, the nfs file
       system expects a binary argument of type  struct  nfs_mount_data.   The
       program   mount  itself  parses  the  following  options  of  the  form
       'tag=value',  and  puts  them  in  the  structure  mentioned:  rsize=n,
       wsize=n,   timeo=n,   retrans=n,  acregmin=n,  acregmax=n,  acdirmin=n,
       acdirmax=n, actimeo=n, retry=n,  port=n,  mountport=n,  mounthost=name,
       mountprog=n,  mountvers=n,  nfsprog=n, nfsvers=n, namlen=n.  The option
       addr=n is accepted but ignored.  Also the  following  Boolean  options,
       possibly  preceded  by  no  are  recognized:  bg, fg, soft, hard, intr,
       posix, cto, ac, tcp, udp, lock.  For details, see nfs(5).

       Especially useful options include

       rsize=32768,wsize=32768
              This causes the NFS client to try to negotiate a buffer size  up
              to the size specified.  A large buffer size does improve perfor-
              mance, but both the server and client have to  support  it.   In
              the case where one of these does not support the size specified,
              the size negotiated will be the largest that both support.

       intr   This will allow NFS operations (on hard  mounts)  to  be  inter-
              rupted while waiting for a response from the server.

       nolock Do not use locking. Do not start lockd.


Mount options for nfs4

       Instead of a textual option string, parsed by the kernel, the nfs4 file
       system expects a binary argument of type struct  nfs4_mount_data.   The
       program   mount  itself  parses  the  following  options  of  the  form
       'tag=value',  and  puts  them  in  the  structure  mentioned:  rsize=n,
       wsize=n,   timeo=n,   retrans=n,  acregmin=n,  acregmax=n,  acdirmin=n,
       acdirmax=n, actimeo=n, retry=n, port=n, proto=n,  clientaddr=n,  sec=n.
       The  option addr=n is accepted but ignored.  Also the following Boolean
       options, possibly preceded by no are recognized: bg,  fg,  soft,  hard,
       intr, cto, ac, For details, see nfs(5).

       Especially useful options include

              NTFS  suppresses  names  that  contain unconvertible 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  file  system  distinguishes  between
              upper  and lower case. The 8.3 alias names are presented as hard
              links instead of being suppressed.

       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.  The reiserfs mount options are
       more fully described at http://www.namesys.com/mount-options.html.

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

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

              rupasov

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

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

       no_unhashed_relocation
              Tunes the block allocator. This may provide performance improve-
              ments 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 file system. Mainly used by reiserfsck.

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


Mount options for romfs

       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 con-
              given  in  bytes, and rounded down to entire pages.  The default
              is half of the memory.

       nr_blocks=
              Set number of blocks.

       nr_inodes=
              Set number of inodes.

       mode=  Set initial permissions of the root directory.


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.
              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).

              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

       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.

       The default is "lower".


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  file  system (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  file  system (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 val-
              ues  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  disabled  for  backward
              compatibility on-disk) an "opportunistic" improvement to be made
              in the way inline extended attributes are stored on-disk.   When
              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 behaviour 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_blk-
              size  by  stat(2)  will  be  as  small as possible to allow user
              applications to avoid  inefficient  read/modify/write  I/O.   If
              largeio  is  specified, a filesystem that has a swidth specified
              will return the swidth value (in bytes) in  st_blksize.  If  the
              filesystem  does not have a swidth specified but does specify an
              allocsize then allocsize (in bytes) will  be  returned  instead.
              If  neither  of these two options are specified, then filesystem
              will behave as if nolargeio was specified.

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

       logbsize=value
              Set  the  size of each in-memory log buffer.  Size may be speci-
              fied in bytes, or in kilobytes with a "k" suffix.   Valid  sizes
              for  version  1  and  version  2  logs are 16384 (16k) and 32768
              (32k).  Valid sizes for version 2 logs also include 65536 (64k),
              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 file systems using the file sys-
              tem uuid.  This is useful to mount LVM snapshot volumes.

       osyncisdsync
              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 speci-


THE LOOP DEVICE

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

         mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024

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

       This type of mount knows about three options, namely loop,  offset  and
       encryption,  that are really options to losetup(8).  (These options can
       be used in addition to those specific to the filesystem type.)

       If no explicit loop device is mentioned (but just an option  '-o  loop'
       is  given), then mount will try to find some unused loop device and use
       that.  If you are not so unwise as to make /etc/mtab a symbolic link to
       /proc/mounts  then  any loop device allocated by mount will be freed by
       umount.  You can also free a loop device by hand, using  'losetup  -d',
       see losetup(8).


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 or missing nfs support in mount

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded


FILES

       /etc/fstab        file system table

       /etc/mtab         table of mounted file systems

       /etc/mtab~        lock file

       /etc/mtab.tmp     temporary file

       /etc/filesystems  a list of filesystem types to try

       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.


HISTORY

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


Linux 2.6 2004-12-16 MOUNT(8)



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