mount (manpage)

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mount - mount a file system


  • mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
  • mount [-fnrsvw] [-o options [,...]] device | dir
  • mount [-fnrsvw] [-t vfstype] [-o options] device dir


All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the 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 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 sub-mounts 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.

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

mount --move olddir newdir

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 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 contains 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


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 programs mount and umount maintain a list of currently mounted file systems in the file /etc/mtab. If no arguments 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). 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 working with the loop device will be less convenient, and using the "user" option will fail.


       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

       Options available for the mount command:

      -V     Output version.

       -h     Print a help message.

       -v     Verbose mode.

       -p num If the mount requires a passphrase to be entered, read it from file descriptor num instead of from the terminal.

       -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  time-
              outs  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 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.

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

       -l     Add the ext2, ext3 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 or ext3 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 example 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 filesystems support this option. This option exists for  support  of  the  Linux  autofs-based  auto-

       -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.

       -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 vfstype
              The argument following the -t is used to indicate the file system type.  The file system types which are  currently
              supported  include:  adfs,  affs, autofs, coda, coherent, cramfs, devpts, efs, ext, ext2, ext3, hfs, hpfs, iso9660,
              jfs, minix, msdos, ncpfs, nfs, 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 filesystem type is required.  For a few types however (like nfs, smbfs, ncpfs) ad hoc code  is  necessary.  The
              nfs  ad  hoc  code  is built in, but 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 and nfs).  If /etc/filesystems ends in a  line
              with a single * only, mount will read /proc/filesystems afterwards.

              The  auto  type  may be useful for user-mounted floppies.  Creating a file /etc/filesystems can be useful to change
              the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you  use  a  kernel  module  autoloader.
              Warning: the probing uses a heuristic (the presence of appropriate `magic'), and could recognize the wrong filesys-
              tem 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

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

       -O     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 file systems except those which have the option _netdev specified in the options field in the /etc/fstab

              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 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 (but not every file system actually honors them - e.g., the sync option today has  effect  only  for  ext2,
              ext3 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.

                     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).

                     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).

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

              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 direct execution of any binaries on the mounted file system.  (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  /

              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
                     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. It does not change device or mount point.

              ro     Mount the file system read-only.

              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.

                     All directory updates within the file system should be done synchronously.  This affects the following  sys-
                     tem 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).

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

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

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

       --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.

       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

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
              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 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.

              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.

              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...

              Print an informational message for each successful mount.

              Prefix used before volume name, when following a link.

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

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

              Give explicitly the location of the root block.

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

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

Mount options for coherent

Mount options for devpts
       The devpts file system is a pseudo file system, 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.

              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  Check filesystem (block and inode bitmaps) at mount time.

       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
              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; 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  set-
              gid bit set if it is a directory itself.

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

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

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

       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  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.   (Ear-
              lier, 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:

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

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

       noload Do not load the ext3 file system's journal on mounting.

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

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

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

                     Data ordering is not preserved - data may be written into the main file system after its metadata  has  been
                     committed  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.

              Sync all data and metadata every nrsec seconds. The default value is 5 seconds. Zero means 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 / blocksize=1024 / blocksize=2048
              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.)

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

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

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

              Three different levels of pickyness can be chosen:

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

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

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

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

       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 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 file systems mounted in binary mode, a conversion tool (fromdos/todos) is available.

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

              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!

              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.

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

       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.

              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.)

              Set  the  umask (the bitmask of the permissions that are not present). The default is the umask of the current pro-
              cess.  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 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.

              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.

              Disable the use of Microsoft Joliet 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 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 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.

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

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

              Set the block size to the indicated value.  (Default: 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 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.

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

              Session begins from sector xxx. (Since 2.3.4.)

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

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

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

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

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

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

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

       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.)

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

Mount options for minix

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 sys-
       tem 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 constructed 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

              This will make your nfs connection faster than with the default buffer size of 4096.  (NFSv2  does  not  work  with
              larger values of rsize and wsize.)

       hard   The  program accessing a file on a NFS mounted file system will hang when the server crashes. The process cannot be
              interrupted or killed unless you also specify intr.  When the NFS server is back online the program  will  continue
              undisturbed from where it was. This is probably what you want.

       soft   This option allows the kernel to time out if the nfs server is not responding for some time. The time can be speci-
              fied with timeo=time.  This option might be useful if your nfs server sometimes doesn't respond or will be rebooted
              while some process tries to get a file from the server.  Usually it just causes lots of trouble.

       nolock Do not use locking. Do not start lockd.

Mount options for ntfs
              Character  set  to  use  when  returning file names.  Unlike VFAT, NTFS suppresses names that contain unconvertible
              characters. Deprecated.

              New name for the option earlier called iocharset.

       utf8   Use UTF-8 for converting file names.

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

              If enabled (posix=1), the 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

       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.

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

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

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

              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 system.

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

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

              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.

              Replay the transactions which are in the journal, but do not actually mount the file system. Mainly used  by  reis-

              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

Mount options for romfs

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

Mount options for sysv

Mount options for tmpfs
       The following parameters accept a suffix k, m or g for Ki, Mi, Gi (binary kilo, mega and  giga)  and  can  be  changed  on

              Override  default  maximum  size  of the filesystem.  The size is given in bytes, and rounded down to entire pages.
              The default is half of the memory.

              Set number of blocks.

              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.

              Show deleted files in lists.

              Unset strict conformance.

              Set the NLS character set.

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

       novrs  Skip volume sequence recognition.

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

              Override standard anchor location. Default: 256.

              Override the VolumeDesc location. (unused)

              Override the PartitionDesc location. (unused)

              Set the last block of the filesystem.

              Override the fileset block location. (unused)

              Override the root directory location. (unused)

Mount options for ufs
              UFS  is  a  file  system widely used in different operating systems.  The problem are differences among implementa-
              tions. 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).

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

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

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

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

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

              Set behaviour on error:

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

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

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

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

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

       posix  Allow two files with names that only differ in case.

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

       utf8   UTF8  is  the  filesystem  safe 8-bit encoding of Unicode that is used by the console. It can be be enabled for the
              filesystem with this option.  If `uni_xlate' gets set, UTF8 gets disabled.


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

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

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

              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

Mount options for xfs
              Sets the preferred buffered I/O size (default size is 64K).  size must be expressed as the logarithm (base2) of the
              desired  I/O  size.   Valid values for this option are 14 through 16, inclusive (i.e. 16K, 32K, and 64K bytes).  On
              machines with a 4K pagesize, 13 (8K bytes) is also a valid size.  The preferred  buffered  I/O  size  can  also  be
              altered on an individual file basis using the ioctl(2) system call.

       dmapi  /  xdsm
              Enable the DMAPI (Data Management API) event callouts.

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

              Set  the  size  of  each in-memory log buffer.  Valid sizes are 16384 (16K) and 32768 (32K).  The default value for
              machines with more than 32MB of memory is 32768, machines with less memory use 16384 by default.

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

              Data allocations will not be aligned at stripe unit boundaries.
              Access timestamps are not updated when a file is read.

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

       nouuid Ignore the filesystem uuid. This avoids errors for duplicate uuids.

              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 in effect, timestamp
              updates from O_SYNC writes can be lost if the system crashes.

       quota / usrquota / uqnoenforce
              User disk quota accounting enabled, and limits (optionally) enforced.

       grpquota / gqnoenforce
              Group disk quota accounting enabled and limits (optionally) enforced.

       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.

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

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

         mount /tmp/fdimage /mnt -t 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).
       If the mount requires a passphrase, you will be prompted for one unless you specify a file descriptor to read from instead
       with the --pass-fd option.  (These options can be used in addition to those specific to the filesystem type.)

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

       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

       /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

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

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

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

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

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

       A mount command existed in Version 5 AT&T UNIX.
  • Version: Linux 2.6 ... 2004-12-16