mkdosfs - create an MS-DOS file system under Linux

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mkdosfs - create an MS-DOS file system under Linux

mkdosfs|mkfs.msdos|mkfs.vfat [ -a ] [ -A ] [ -b sector-of-backup ] [ -c
] [ -l filename ] [ -C ] [ -f number-of-FATs ] [ -F FAT-size ] [ -h
number-of-hidden-sectors ] [ -i volume-id ] [ -I ] [ -m message-file ]
[ -n volume-name ] [ -r root-dir-entries ] [ -R number-of-reserved-sec‐
tors ] [ -s sectors-per-cluster ] [ -S logical-sector-size ] [ -v ]
device [ block-count ]

mkdosfs is used to create an MS-DOS file system 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, mkdosfs automatically determines the file sys‐
tem size.

-a Normally, for any filesystem except very small ones, mkdosfs
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 file system. This is default
if mkdosfs 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, mkdosfs 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 file systems are managed by raising the log‐
ical sector size. Under Atari format, an Atari-compatible
serial number for the file system is generated, and a 12 bit FAT
is used only for file systems 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 sec‐
tor fields aren't written, and a boot message (option -m) is

-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‐

-c Check the device for bad blocks before creating the file system.

-C Create the file given as device on the command line, and write
the to-be-created file system to it. This can be used to create
the new file system 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 file system wouldn't be
known. The file created is a sparse file, which actually only
contains the meta-data areas (boot sector, FATs, and root direc‐
tory). 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.

-f number-of-FATs
Specify the number of file allocation tables in the file system.
The default is 2. Currently the Linux MS-DOS file system 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, mkdosfs will automatically
select between 12, 16 and 32 bit, whatever fits better for the
file system 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 file system; volume-id
is a 32-bit hexadecimal number (for example, 2e24ec82). The
default is a number which depends on the file system creation

-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. mkdosfs 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 file system can
go directly to the whole disk. Under other OSes this is known
as the 'superfloppy' format.

This switch will force mkdosfs 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 file
system 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.

-n volume-name
Sets the volume name (label) of the file system. 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.

mkdosfs can not create boot-able file systems. This isn't as easy as
you might think at first glance for various reasons and has been dis‐
cussed a lot already. mkdosfs simply will not support it ;)

Dave Hudson - ; modified by Peter Anvin
. Fixes and additions by Roman Hodek
for Debian/GNU Linux.

mkdosfs is based on code from mke2fs (written by Remy Card -
) which is itself based on mkfs (written by Linus
Torvalds - ).

dosfsck(8), dosfslabel(8), mkfs(8)

Version 2.x 5 May 1995 MKDOSFS(8)