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

NAME
       mkfs.fat - create an MS-DOS FAT filesystem

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

DESCRIPTION
       mkfs.fat is used to create a FAT filesystem on a device or in an image
       file.  DEVICE is the special file corresponding to the device (e.g.
       /dev/sdXX) or the image file (which does not need to exist when the
       option -C is given).  BLOCK-COUNT is the number of blocks on the device
       and size of one block is always 1024 bytes, independently of the sector
       size or the cluster size.  Therefore BLOCK-COUNT specifies size of
       filesystem in KiB unit and not in the number of sectors (like for all
       other mkfs.fat options).	 If omitted, mkfs.fat automatically chooses a
       filesystem size to fill the available space.

       Two different variants of the FAT filesystem are supported.  Standard
       is the FAT12, FAT16 and FAT32 filesystems as defined by Microsoft and
       widely used on hard disks and removable media like USB sticks and SD
       cards.  The other is the legacy Atari variant used on Atari ST.

       In Atari mode, 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.  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 ignored.

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 partition 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  Select using the Atari variation of the FAT filesystem if that
	   isn't active already, otherwise select standard FAT filesystem.
	   This is selected by default if mkfs.fat is run on 68k Atari Linux.

       -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.  If
	   there is a free space available after the backup boot sector then
	   backup of the FAT32 info sector is put after the backup boot
	   sector, usually at sector 7.	 The backup must be within the range
	   of reserved sectors.	 Value 0 completely disables creating of
	   backup boot and info FAT32 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 create 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 device, or mounted through a loop device.

       -D DRIVE-NUMBER
	   Specify the BIOS drive number to be stored in the FAT boot sector.
	   For hard disks and removable medias it is usually 0x80–0xFF (0x80
	   is first hard disk C:, 0x81 is second hard disk D:, ...), for
	   floppy devices or partitions to be used for floppy emulation it is
	   0x00–0x7F (0x00 is first floppy A:, 0x01 is second floppy B:).

       -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.

       -g HEADS/SECTORS-PER-TRACK
	   Specify HEADS and SECTORS-PER-TRACK numbers which represents disk
	   geometry of DEVICE.	Both numbers are stored into the FAT boot
	   sector.  Number SECTORS-PER-TRACK is used also for aligning the
	   total count of FAT sectors.	By default disk geometry is read from
	   DEVICE itself.  If it is not available then LBA-Assist Translation
	   and translation table from the SD Card Part 2 File System
	   Specification based on total number of disk sectors is used.

       -h NUMBER-OF-HIDDEN-SECTORS
	   Specify the number of so-called hidden sectors, as stored in the
	   FAT boot sector: this number represents the beginning sector of the
	   partition containing the file system.  Normally this is an offset
	   (in sectors) relative to the start of the disk, although for MBR
	   logical volumes contained in an extended partition of type 0x05 (a
	   non-LBA extended partition), a quirk in the MS-DOS implementation
	   of FAT requires it to be relative to the partition's immediate
	   containing Extended Boot Record.  Boot code and other software
	   handling FAT volumes may also rely on this field being set up
	   correctly; most modern FAT implementations will ignore it.  By
	   default, if the DEVICE is a partition block device, mkfs.fat uses
	   the partition offset relative to disk start.	 Otherwise, mkfs.fat
	   assumes zero.  Use this option to override this behaviour.

       -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  Ignore and disable safety checks.  By default mkfs.fat refuses to
	   create a filesystem on a device with partitions or virtual mapping.
	   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 without 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.

       --mbr[=y|yes|n|no|a|auto]
	   Fill (fake) MBR table with disk signature one partition which
	   starts at sector 0 (includes MBR itself) and spans whole disk
	   device.  It is needed only for non-removable disks used on
	   Microsoft Windows systems and only when formatting whole
	   unpartitioned disk.	Location of the disk signature and partition
	   table overlaps with the end of the first FAT sector (boot code
	   location), therefore there is no additional space usage.  Default
	   is auto mode in which mkfs.fat put MBR table only for non-removable
	   disks when formatting whole unpartitioned disk.

       -n VOLUME-NAME
	   Sets the volume name (label) of the filesystem.  The volume name
	   can be up to 11 characters long.  Supplying an empty string, a
	   string consisting only of white space or the string "NO NAME" as
	   VOLUME-NAME has the same effect as not giving the -n option.	 The
	   default is no label.

       --codepage=PAGE
	   Use DOS codepage PAGE to encode label.  By default codepage 850 is
	   used.

       -r ROOT-DIR-ENTRIES
	   Select the minimal number of entries available in the root
	   directory.  The default is 112 or 224 for floppies and 512 for hard
	   disks.  Note that this is minimal number and it may be increased by
	   mkfs.fat due to alignment of structures.  See also mkfs.fat option
	   -a.

       -R NUMBER-OF-RESERVED-SECTORS
	   Select the minimal number of reserved sectors.  With FAT32 format
	   at least 2 reserved sectors are needed, the default is 32.
	   Otherwise the default is 1 (only the boot sector).  Note that this
	   is minimal number and it may be increased by mkfs.fat due to
	   alignment of structures.  See also mkfs.fat option -a.

       -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.

       --offset SECTOR
	   Write the filesystem at a specific sector into the device file.
	   This is useful for creating a filesystem in a partitioned disk
	   image without having to set up a loop device.

       --variant TYPE
	   Create a filesystem of variant TYPE.	 Acceptable values are
	   standard and atari (in any combination of upper/lower case).	 See
	   above under DESCRIPTION for the differences.

       --help
	   Display option summary and exit.

       --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.

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 others.  Current
       maintainers are Andreas Bombe <aeb@debian.org> and Pali Rohár
       <pali.rohar@gmail.com>.

dosfstools 4.2			  2021-01-31			   MKFS.FAT(8)