mount

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NAME

       mount - mount a file system


SYNOPSIS

       mount [-hV]

       mount -a [-fnrvw] [-t vfstype]
       mount [-fnrvw] [-o options [,...]] device | dir
       mount [-fnrvw] [-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 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 [-t type]
       lists all mounted file systems (of type type) - see below.

       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 spe-
       cial  device),  like /dev/sda1, but there are other possi-
       bilities. For example, in the case of an NFS mount, device
       may look like knuth.cwi.nl:/dir.

       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]
       (usually  given  in  a bootscript) causes all file systems
       mentioned in fstab (of the proper type) to be  mounted  as
       indicated, except for those whose line contains the noauto
       keyword.

       (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,
       then 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).

       The programs mount and umount maintain a list of currently
       mounted file systems in the file /etc/mtab.  If  no  argu-
       ments  are given to mount, this list is printed.  When the
       proc filesystem is  mounted  (say  at  /proc),  the  files
       /etc/mtab and /proc/mounts have very similar contents. The
       former has somewhat more information, such  as  the  mount
       options  used,  but is not necessarily up-to-date (cf. the
       -n option below).



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     Verbose mode.

       -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 determine what the
              mount command is trying to do.

       -n     Mount without writing in /etc/mtab.  This is neces-
              sary  for  example when /etc is on a read-only file
              system.

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

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

       -t vfstype
              The argument following the -t is used  to  indicate
              the  file system type.  The file system types which
              are   currently    supported    are    listed    in
              linux/fs/filesystems.c:  minix,  ext,  ext2, xiafs,
              hpfs, fat, msdos, umsdos, vfat, proc, nfs, iso9660,
              smb,  ncp,  affs, ufs, sysv, xenix, coherent.  Note
              that the last three are equivalent and  that  xenix
              and  coherent  will be removed at some point in the
              future -- use sysv instead.

              The type iso9660 is the default.  If no  -t  option
              is  given,  or  if  the auto type is specified, the
              superblock  is  probed  for  the  filesystem   type
              (minix, ext, ext2, xia, iso9660 are supported).  If
              this probe fails and /proc/filesystems exists, then
              all  of the filesystems listed there will be tried,
              except for those that are  labeled  "nodev"  (e.g.,
              proc and nfs).

              Note  that  the  auto  type may be useful for user-
              mounted floppies.   Warning:  the  probing  uses  a
              heuristic  (the  presence  of appropriate `magic'),
              and could recognize the wrong filesystem type.

              More than one type may be specified in a comma sep-
              arated  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.)

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

       -o     Options  are specified with a -o flag followed by a
              comma separated 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:

              async  All  I/O  to  the file system should be done
                     asynchronously.

              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.

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

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

              noexec Do  not  allow  execution of any binaries on
                     the mounted file system.  This option  might
                     be useful for a server that has file systems
                     containing binaries for architectures  other
                     than its own.

              nosuid Do  not  allow  set-user-identifier  or set-
                     group-identifier bits to take effect.

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

              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 writeable.

              ro     Mount the file system read-only.

              rw     Mount the file system read-write.

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

              sync   All I/O to the file system  should  be  done
                     synchronously.

              user   Allow  an  ordinary  user  to mount the file
                     system.  This  option  implies  the  options
                     noexec, nosuid, and nodev (unless overridden
                     by subsequent options, as in the option line
                     user,exec,dev,suid).



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.



Mount options for affs

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

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

       mode=value
              Set the mode of all files to value  &  0777  disre-
              garding  the original permissions.  Add search per-
              mission 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 system.

       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.



Mount options for coherent

       None.




Mount options for ext

       None.  Note that the `ext' file system is obsolete.  Don't
       use it.



Mount options for ext2

       The  `ext2' file system is the standard Linux file system.
       Due to a kernel bug, it may be mounted with  random  mount
       options (Linux 2.0).

       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 sys-
              tem,  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 / check=normal / check=strict
              Set checking level. When  at  least  one  of  these
              options is set (and check=normal is set by default)
              the inodes and  blocks  bitmaps  are  checked  upon
              mount  (which can take half a minute or so on a big
              disk).  With strict  checking,  block  deallocation
              checks  that the block to free is in the data zone.

       check=none / nocheck
              No checking is done.

       debug  Print debugging info upon each (re)mount.

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

       grpid or bsdgroups / nogrpid or 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; other-
              wise (the default) it takes the fsgid of  the  cur-
              rent  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.

       resgid=n and resuid=n
              The ext2 file system 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  dam-
              aged.   Usually, copies of the superblock are found
              every 8192 blocks: in block  1,  8193,  16385,  ...
              (Thus,  one  gets  hundreds  or  even  thousands of
              copies of the superblock on a big filesystem. I  do
              not  know  of  options  to  mke2fs that would cause
              fewer copies to be written.)

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



Mount options for fat

       blocksize=512 / blocksize=1024
              Set blocksize (default 512).

       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.

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

              r[elaxed]
                     Upper and lower case are accepted and equiv-
                     alent, 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.)

       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 avail-
              able:

              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-ker-
              nel text conversion.  Several people have had their
              data ruined by this translation. Beware!

              For file systems mounted in binary mode, a  conver-
              sion tool (fromdos/todos) is available.

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

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

       conv=binary / conv=text / conv=auto
              For  conv=text, delete some random CRs (in particu-
              lar, 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

       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.

       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  informa-
              tion found in the Rock Ridge extensions.  (Default:
              uid=0,gid=0.)

       map=n[ormal] / map=o[ff]
              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.)

       mode=value
              For non-Rock Ridge  volumes,  give  all  files  the
              indicated  mode.   (Default:  read  permission  for
              everybody.)

       unhide Also show hidden and associated files.

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

       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 set-
              tings  used  to be very dangerous, often 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.   The `cruft'
              option is set automatically if the entire CDROM has
              a  weird size (negative, or more than 800MB). It is
              also set when volume sequence numbers other than  0
              or 1 are seen.



Mount options for minix

       None.



Mount options for msdos

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



Mount options for ncp

       Just like nfs, the ncp  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  (2.5k) does not know anything
       about ncp.



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, moun-
       thost=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.  For details, see nfs(5).

       Especially useful options include

       rsize=8192,wsize=8192
              This will make your nfs connection much faster than
              with the default buffer size of 1024.

       soft   This option allows the kernel to time  out  if  the
              nfs  server is not responding for some time, other-
              wise it will try forever. The time can be specified
              with timeo=time.  This option is useful if your nfs
              server  sometimes  doesn't  respond  or   will   be
              rebooted  while  some  process  tries to get a file
              from the server.



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 smb

       Just  like  nfs,  the  smb 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 (2.5k)  does  not  know  anything
       about smb.



Mount options for sysv

       None.



Mount options for ufs

       None.



Mount options for umsdos

       See mount options for msdos.



Mount options for vfat

       First  of  all,  the mount options for fat are recognized.
       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.

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



Mount options for xenix

       None.



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.



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  los-
       etup(8).   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.



FILES

       /etc/fstab file system table
       /etc/mtab table of mounted file systems
       /etc/mtab~ lock file
       /etc/mtab.tmp temporary file


SEE ALSO

       mount(2),   umount(2),   fstab(5),  umount(8),  swapon(8),
       nfs(5), mountd(8), nfsd(8),  mke2fs(8),  tune2fs(8),  los-
       etup(8)


BUGS

       It  is  possible  for  a  corrupted file system to cause a
       crash.

       Some Linux file systems don't support -o sync (the  ext2fs
       does  support  synchronous updates (a la BSD) when mounted
       with the sync option).

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


HISTORY

       A mount command appeared in Version 6 AT&T UNIX.
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