Section: Maintenance Commands (8)
- create an MS-DOS filesystem under Linux
is used to create an MS-DOS filesystem under Linux on a device
(usually a disk partition).
is the special file corresponding to the device (e.g. /dev/sdXX).
is the number of blocks on the device.
If omitted, mkfs.fat
automatically determines the filesystem size.
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
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.
Use Atari variation of the MS-DOS filesystem.
This is default if mkfs.fat is run on an Atari, then this option turns off
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 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 sectors.
Check the device for bad blocks before creating the filesystem.
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
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.
This value is usually 0x80 for hard disks and 0x00 for floppy devices or
partitions 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 sectors, 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.
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 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 reserved 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.
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.
Display option summary and exit.
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.
simply will not support it ;)
The home for the dosfstools
project is its
GitHub project page
were written by
The current maintainer is