MKFS.FAT(8) dosfstools MKFS.FAT(8)NAME
mkfs.fat - create an MS-DOS filesystem under Linux
SYNOPSIS
mkfs.fat [ -a ] [ -A ] [ -b sector-of-backup ] [ -c ] [ -l filename ] [
-C ] [ -f number-of-FATs ] [ -F FAT-size ] [ -h number-of-hidden-sec‐
tors ] [ -i volume-id ] [ -I ] [ -m message-file ] [ -n volume-name ] [
-r root-dir-entries ] [ -R number-of-reserved-sectors ] [ -s sectors-
per-cluster ] [ -S logical-sector-size ] [ -v ] 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/hdXX). block-count is the number of blocks on
the device. If omitted, mkfs.fat automatically determines the filesys‐
tem 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 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 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 logi‐
cal 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
ignored.
-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 sec‐
tors.
-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 other‐
wise 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 never‐
theless 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.
-f number-of-FATs
Specify the number of file allocation tables in the filesystem.
The default is 2. Currently the Linux MS-DOS filesystem does
not support more than 2 FATs.
-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 sectors, this option allows you to satisfy
them. Assumes ´0´ if no value is given on the command line.
-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 without having properly installed an operating sys‐
tem. 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.
-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 reserved sectors are needed, the default is 32. Other‐
wise 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.
-v Verbose execution.
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 dis‐
cussed a lot already. mkfs.fat simply will not support it ;)
AUTHOR
Dave Hudson - <dave@humbug.demon.co.uk>; modified by Peter Anvin
<hpa@yggdrasil.com>. Fixes and additions by Roman Hodek
<roman@hodek.net> for Debian GNU/Linux.
ACKNOWLEDGMENTS
mkfs.fat is based on code from mke2fs (written by Remy Card -
<card@masi.ibp.fr>) which is itself based on mkfs (written by Linus
Torvalds - <torvalds@cs.helsinki.fi>).
SEE ALSOfsck.fat(8), fatlabel(8), mkfs(8)3.0.19 2013-06-11 MKFS.FAT(8)
