Section: User Commands (1)
mformat - add an MSDOS filesystem to a low-level formatted floppy disk
Note of warning
This manpage has been automatically generated from mtools's texinfo
documentation, and may not be entirely accurate or complete. See the
end of this man page for details.
The mformat command is used to add an MS-DOS file system to a
low-level formatted diskette. Its syntax is:
mformat [-t cylinders|-T tot_sectors] [-h heads] [-s sectors]
[-f size] [-1] [-4] [-8]
[-F] [-S sizecode]
[-N serial_number] [-a]
[-C] [-H hidden_sectors] [-I fsVersion]
[-r root_sectors] [-L fat_len]
[-B boot_sector] [-k]
[-X] [-2 sectors_on_track_0] [-3]
[-0 rate_on_track_0] [-A rate_on_other_tracks]
Mformat adds a minimal MS-DOS file system (boot sector, FAT, and
root directory) to a diskette that has already been formatted by a Unix
The following options are supported: (The S, 2, 1 and M options may not
exist if this copy of mtools has been compiled without the USE_2M
The following options are the same as for MS-DOS's format command:
Specifies the volume label. A volume label identifies the disk and can
be a maximum of 11 characters. If you omit the -v switch, mformat will
assign no label to the disk.
Specifies the size of the DOS file system to format. Only a certain
number of predefined sizes are supported by this flag; for others use
the -h/-t/-s flags. The following sizes are supported:
160K, single-sided, 8 sectors per track, 40 cylinders (for 5 1/4 DD)
160K, single-sided, 9 sectors per track, 40 cylinders (for 5 1/4 DD)
320K, double-sided, 8 sectors per track, 40 cylinders (for 5 1/4 DD)
360K, double-sided, 9 sectors per track, 40 cylinders (for 5 1/4 DD)
720K, double-sided, 9 sectors per track, 80 cylinders (for 3 1/2 DD)
1200K, double-sided, 15 sectors per track, 80 cylinders (for 5 1/4 HD)
1440K, double-sided, 18 sectors per track, 80 cylinders (for 3 1/2 HD)
2880K, double-sided, 36 sectors per track, 80 cylinders (for 3 1/2 ED)
Specifies the number of tracks on the disk.
Specifies the number of total sectors on the disk. Only one of these 2
options may be specified (tracks or total sectors)
The number of heads (sides).
Specifies the number of sectors per track. If the 2m option is given,
number of 512-byte sector equivalents on generic tracks (i.e. not head 0
track 0). If the 2m option is not given, number of physical sectors per
track (which may be bigger than 512 bytes).
Formats a single side (equivalent to -h 1)
Formats a 360K double-sided disk (equivalent to -f 360). When used
together with -the 1 switch, this switch formats a 180K disk
Formats a disk with 8 sectors per track.
MS-DOS format's q, u and b options are not
supported, and s has a different meaning.
The following options are specific to mtools:
Format the partition as FAT32.
The size code. The size of the sector is 2 ^ (sizecode + 7).
formats the disk as an XDF disk. See section XDF, for more details. The disk
has first to be low-level formatted using the xdfcopy utility included
in the fdutils package. XDF disks are used for instance for OS/2 install
2m format. The parameter to this option describes the number of
sectors on track 0, head 0. This option is recommended for sectors
bigger than normal.
don't use a 2m format, even if the current geometry of the disk is a 2m
Data transfer rate on track 0
Data transfer rate on tracks other than 0
software sector size. This parameter describes the sector size in bytes used
by the MS-DOS file system. By default it is the physical sector size.
Uses the requested serial number, instead of generating one
If this option is given, an Atari style serial number is generated.
Ataris store their serial number in the OEM label.
creates the disk image file to install the MS-DOS file system on
it. Obviously, this is useless on physical devices such as floppies
and hard disk partitions, but is interesting for image files.
number of hidden sectors. This parameter is useful for formatting hard
disk partition, which are not aligned on track boundaries (i.e. first
head of first track doesn't belong to the partition, but contains a
partition table). In that case the number of hidden sectors is in
general the number of sectors per cylinder. This is untested.
Sets the fsVersion id when formatting a FAT32 drive. In order to find
this out, run minfo on an existing FAT32 drive, and mail me about it, so
I can include the correct value in future versions of mtools.
Sets the size of a cluster (in sectors). If this cluster size would
generate a FAT that too big for its number of bits, mtools automatically
increases the cluster size, until the FAT is small enough. If no
cluster size is specified explicitly, mtools uses a default value as
described in section ``Number of sectors per cluster'' below.
Sets the number of FAT copies. Default is 2. This setting can also be
specified using the MTOOLS_NFATS environment variable.
Sets the size of the root directory (in sectors). Only applicable to 12
and 16 bit FATs. This setting can also be specified using the
MTOOLS_DIR_LEN environment variable.
Sets the length of the FAT.
Use the boot sector stored in the given file or device, instead of using
its own. Only the geometry fields are updated to match the target disks
Keep the existing boot sector as much as possible. Only the geometry
fields and other similar file system data are updated to match the target
Sets the sector number where the backup of the boot sector should be
stored (only relevant on FAT32).
Sets the number of reserved sectors for this filesystem. This must be
at least 1 for non-FAT32 disks, and at least 3 for FAT disks (in order
to accommodate the boot sector, the info sector and the backup boot
Use a non-standard media descriptor byte for this disk. The media
descriptor is stored at position 21 of the boot sector, and as first
byte in each FAT copy. Using this option may confuse DOS or older mtools
version, and may make the disk unreadable. Only use if you know what you
To format a diskette at a density other than the default, you must supply
(at least) those command line parameters that are different from the
Mformat returns 0 on success or 1 on failure.
It doesn't record bad block information to the Fat, use
mbadblocks for that.
Number of sectors per cluster
If the user indicates no cluster size, mformat figures out a default
value for it.
For FAT32 it uses the following table to determine the number of
sectors per cluster, depending on the total number of sectors on the
more than 32*1024*1024*2: 64 sectors
between 16*1024*1024*2 and 32*1024*1024*2: 32 sectors
between 8*1024*1024*2 and 16*1024*1024*2: 16 sectors
between 260*1024*2 and 81024*1024*2: 1 sectors
This is derived from information on page 20 of Microsoft's
fatgen103 document, which currently can be found at the
For FAT12 and FAT16, mformat uses an iterative approach, where it
starts with a set value, which it doubles until it is able to fill up
the disk using that cluster size and a number of cluster less than the
The starting value is 1 for disks with one head or less than 2000
sectors, and 2 for disks with more than one head, and more than 2000
The number of sectors per cluster cannot go beyond 128.
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