MKFS.FAT(8)                     System Manager's Manual                     MKFS.FAT(8)

NAME
       mkfs.fat - create an MS-DOS filesystem under Linux

SYNOPSIS
       mkfs.fat [OPTIONS] DEVICE [BLOCK-COUNT]

DESCRIPTION
       mkfs.fat is used to create an MS-DOS filesystem under Linux on a device (usually
       a disk partition).  DEVICE is the special file corresponding to the device (e.g.
       /dev/sdXX).   BLOCK-COUNT  is  the  number of blocks on the device.  If omitted,
       mkfs.fat automatically determines the filesystem size.

OPTIONS
       -a  Normally, for any filesystem except very small ones, mkfs.fat will align all
           the data structures to cluster size, to make sure that as long as the parti‐
           tion is properly aligned, so will all the data structures in the filesystem.
           This  option  disables  alignment;  this may provide a handful of additional
           clusters of storage at the expense of a significant performance  degradation
           on RAIDs, flash media or large-sector hard disks.

        -A Use  Atari  variation of the MS-DOS filesystem.  This is default if mkfs.fat
           is run on an Atari, then this option turns off Atari format.  There are some
           differences  when using Atari format: If not directed otherwise by the user,
           mkfs.fat will always use 2 sectors per cluster, since  GEMDOS  doesn't  like
           other  values  very  much.   It will also obey the maximum number of sectors
           GEMDOS can handle.  Larger filesystems are managed by  raising  the  logical
           sector  size.  Under Atari format, an Atari-compatible serial number for the
           filesystem is generated, and a 12 bit FAT is used only for filesystems  that
           have  one of the usual floppy sizes (720k, 1.2M, 1.44M, 2.88M), a 16 bit FAT
           otherwise.  This can be overridden with the  -F  option.   Some  PC-specific
           boot  sector  fields  aren't  written, and a boot message (option -m) is ig‐
           nored.

       -b SECTOR-OF-BACKUP
           Selects the location of the backup boot sector for FAT32.   Default  depends
           on  number of reserved sectors, but usually is sector 6.  The backup must be
           within the range of reserved sectors.

       -c  Check the device for bad blocks before creating the filesystem.

       -C  Create the file given as DEVICE on the command line, and  write  the  to-be-
           created  filesystem to it.  This can be used to create the new filesystem in
           a file instead of on a real device, and to avoid using dd in advance to cre‐
           ate  a  file of appropriate size.  With this option, the BLOCK-COUNT must be
           given, because otherwise the intended size of  the  filesystem  wouldn't  be
           known.   The file created is a sparse file, which actually only contains the
           meta-data areas (boot sector, FATs, and root directory).  The data  portions
           won't be stored on the disk, but the file nevertheless will have the correct
           size.  The resulting file can be copied later to a floppy disk or other  de‐
           vice, or mounted through a loop device.

       -D DRIVE-NUMBER
           Specify  the  BIOS  drive  number to be stored in the FAT boot sector.  This
           value is usually 0x80 for hard disks and 0x00 for floppy devices  or  parti‐
           tions to be used for floppy emulation.

       -f NUMBER-OF-FATS
           Specify the number of file allocation tables in the filesystem.  The default
           is 2.

       -F FAT-SIZE
           Specifies the type of file allocation tables used (12, 16 or  32  bit).   If
           nothing  is specified, mkfs.fat will automatically select between 12, 16 and
           32 bit, whatever fits better for the filesystem size.

       -h NUMBER-OF-HIDDEN-SECTORS
           Select the number of hidden sectors in the volume.  Apparently some  digital
           cameras  get indigestion if you feed them a CF card without such hidden sec‐
           tors, this option allows you to satisfy them.

       -i VOLUME-ID
           Sets the volume ID of the newly created filesystem; VOLUME-ID  is  a  32-bit
           hexadecimal  number  (for example, 2e24ec82).  The default is a number which
           depends on the filesystem creation time.

       -I  It is typical for fixed disk devices to be partitioned so, by  default,  you
           are not permitted to create a filesystem across the entire device.  mkfs.fat
           will complain and tell you that it refuses to work.  This is different  when
           using  MO  disks.   One  doesn't  always  need  partitions on MO disks.  The
           filesystem can go directly to the whole disk.   Under  other  OSes  this  is
           known  as the 'superfloppy' format.  This switch will force mkfs.fat to work
           properly.

       -l FILENAME
           Read the bad blocks list from FILENAME.

       -m MESSAGE-FILE
           Sets the message the user receives on attempts to boot this filesystem with‐
           out  having  properly  installed an operating system.  The message file must
           not exceed 418 bytes once line feeds have been converted to carriage return-
           line  feed  combinations, and tabs have been expanded.  If the filename is a
           hyphen (-), the text is taken from standard input.

       -M FAT-MEDIA-TYPE
           Specify the media type to be stored in the FAT boot sector.  This  value  is
           usually  0xF8  for  hard  disks and is 0xF0 or a value from 0xF9 to 0xFF for
           floppies or partitions to be used for floppy emulation.

       -n VOLUME-NAME
           Sets the volume name (label) of the filesystem.  The volume name can  be  up
           to 11 characters long.  The default is no label.

       -r ROOT-DIR-ENTRIES
           Select  the  number of entries available in the root directory.  The default
           is 112 or 224 for floppies and 512 for hard disks.

       -R NUMBER-OF-RESERVED-SECTORS
           Select the number of reserved sectors.  With FAT32 format  at  least  2  re‐
           served  sectors  are  needed, the default is 32.  Otherwise the default is 1
           (only the boot sector).

       -s SECTORS-PER-CLUSTER
           Specify the number of disk sectors per cluster.  Must be a power of 2,  i.e.
           1, 2, 4, 8, ... 128.

       -S LOGICAL-SECTOR-SIZE
           Specify  the  number  of bytes per logical sector.  Must be a power of 2 and
           greater than or equal to 512, i.e. 512, 1024, 2048, 4096,  8192,  16384,  or
           32768.   Values  larger  than 4096 are not conforming to the FAT file system
           specification and may not work everywhere.

       -v  Verbose execution.

       --invariant
           Use constants for normally randomly generated or time  based  data  such  as
           volume  ID  and creation time.  Multiple runs of mkfs.fat on the same device
           create identical results with this option.   Its  main  purpose  is  testing
           mkfs.fat.

       --help
           Display option summary and exit.

BUGS
       mkfs.fat  can not create boot-able filesystems.  This isn't as easy as you might
       think at first glance for various reasons and has been discussed a lot  already.
       mkfs.fat simply will not support it ;)

SEE ALSO
       fatlabel(8)
       fsck.fat(8)

HOMEPAGE
       The   home   for   the   dosfstools   project   is   its   GitHub  project  page
       ⟨https://github.com/dosfstools/dosfstools⟩.

AUTHORS
       dosfstools   were   written   by   Werner    Almesberger    ⟨werner.almesberger@
       lrc.di.epfl.ch⟩,  Roman Hodek ⟨Roman.Hodek@informatik.uni-erlangen.de⟩, and oth‐
       ers.  The current maintainer is Andreas Bombe ⟨aeb@debian.org⟩.

dosfstools 4.1                         2016-01-25                           MKFS.FAT(8)

mkfs.fat 4.1 (2017-01-24)
Usage: mkfs.fat [-a][-A][-c][-C][-v][-I][-l bad-block-file][-b backup-boot-sector]
       [-m boot-msg-file][-n volume-name][-i volume-id]
       [-s sectors-per-cluster][-S logical-sector-size][-f number-of-FATs]
       [-h hidden-sectors][-F fat-size][-r root-dir-entries][-R reserved-sectors]
       [-M FAT-media-byte][-D drive_number]
       [--invariant]
       [--help]
       /dev/name [blocks]