sbin/newfs_msdos/newfs_msdos.8

.\" Copyright (c) 1998 Robert Nordier
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.Dd December 8, 2007
.Dt NEWFS_MSDOS 8
.Os
.Sh NAME
.Nm newfs_msdos
.Nd construct a new MS-DOS (FAT) file system
.Sh SYNOPSIS
.Nm
.Op Fl N
.Op Fl @ Ar offset
.Op Fl B Ar boot
.Op Fl C Ar create-size
.Op Fl F Ar FAT-type
.Op Fl I Ar volid
.Op Fl L Ar label
.Op Fl O Ar OEM
.Op Fl S Ar sector-size
.Op Fl a Ar FAT-size
.Op Fl b Ar block-size
.Op Fl c Ar cluster-size
.Op Fl e Ar dirents
.Op Fl f Ar format
.Op Fl h Ar heads
.Op Fl i Ar info
.Op Fl k Ar backup
.Op Fl m Ar media
.Op Fl n Ar FATs
.Op Fl o Ar hidden
.Op Fl r Ar reserved
.Op Fl s Ar total
.Op Fl u Ar track-size
.Ar special
.Op Ar disktype
.Sh DESCRIPTION
The
.Nm
utility creates a FAT12, FAT16, or FAT32 file system on device or file named
.Ar special ,
using
.Xr disktab 5
entry
.Ar disktype
to determine geometry, if required.
.Pp
If
.Ar special
does not contain a
.Ar / ,
it is assumed to be a device name and
.Ar /dev
is prepended to the name to construct the actual device name.
To work a file in the current directory use
.Ar ./filename
.Pp
The options are as follow:
.Bl -tag -width indent
.It Fl N
Do not create a file system: just print out parameters.
.It Fl @ Ar offset
Build the filesystem at the specified offset in bytes in the device or file.
A suffix s, k, m, g (lower or upper case)
appended to the offset specifies that the
number is in sectors, kilobytes, megabytes or gigabytes, respectively.
.It Fl B Ar boot
Get bootstrap from file.
.It Fl C Ar create-size
Create the image file with the specified size. A suffix character appended
to the size is interpreted as for the
.Fl @
option. The file is created by truncating any existing file with the
same name, seeking just before the required size and writing
a single 0 byte. As a consequence, the space occupied on disk
may be smaller than the size specified as a parameter.
.It Fl F Ar FAT-type
FAT type (one of 12, 16, or 32).
.It Fl I Ar volid
Volume ID, a 32 bit number in decimal or hexadecimal (0x...) format.
.It Fl L Ar label
Volume label (up to 11 characters).
The label should consist of
only those characters permitted in regular DOS (8+3) filenames.
.It Fl O Ar OEM
OEM string (up to 8 characters).
The default is
.Qq Li "BSD  4.4" .
.It Fl S Ar sector-size
Number of bytes per sector.
Acceptable values are powers of 2
in the range 128 through 32768.
.It Fl a Ar FAT-size
Number of sectors per FAT.
.It Fl b Ar block-size
File system block size (bytes per cluster).
This should resolve to an
acceptable number of sectors per cluster (see below).
.It Fl c Ar cluster-size
Sectors per cluster.
Acceptable values are powers of 2 in the range
1 through 128.
If the block or cluster size are not specified, the code
uses a cluster between 512 bytes and 32K depending on
the filesystem size.
.It Fl e Ar dirents
Number of root directory entries (FAT12 and FAT16 only).
.It Fl f Ar format
Specify a standard (floppy disk) format.
The standard formats
are (capacities in kilobytes): 160, 180, 320, 360, 640, 720, 1200,
1232, 1440, 2880.
.It Fl h Ar heads
Number of drive heads.
.It Fl i Ar info
Location of the file system info sector (FAT32 only).
A value of 0xffff signifies no info sector.
.It Fl k Ar backup
Location of the backup boot sector (FAT32 only).
A value
of 0xffff signifies no backup sector.
.It Fl m Ar media
Media descriptor (acceptable range 0xf0 to 0xff).
.It Fl n Ar FATs
Number of FATs.
Acceptable values are 1 to 16 inclusive.
The default
is 2.
.It Fl o Ar hidden
Number of hidden sectors.
.It Fl r Ar reserved
Number of reserved sectors.
.It Fl s Ar total
File system size.
.It Fl u Ar track-size
Number of sectors per track.
.El
.Sh NOTES
If some parameters (e.g. size, number of sectors, etc.) are not specified
through options or disktype, the program tries to generate them
automatically. In particular, the size is determined as the
device or file size minus the offset specified with the
.Fl @
option. When the geometry is not available, it is assumed to be
63 sectors, 255 heads. The size is then rounded to become
a multiple of the track size and avoid complaints by some filesystem code.
.Pp
FAT file system parameters occupy a "Boot Sector BPB (BIOS Parameter
Block)" in the first of the "reserved" sectors which precede the actual
file system.
For reference purposes, this structure is presented
below.
.Bd -literal
struct bsbpb {
    u_int16_t	bps;		/* [-S] bytes per sector */
    u_int8_t	spc;		/* [-c] sectors per cluster */
    u_int16_t	res;		/* [-r] reserved sectors */
    u_int8_t	nft;		/* [-n] number of FATs */
    u_int16_t	rde;		/* [-e] root directory entries */
    u_int16_t	sec;		/* [-s] total sectors */
    u_int8_t	mid;		/* [-m] media descriptor */
    u_int16_t	spf;		/* [-a] sectors per FAT */
    u_int16_t	spt;		/* [-u] sectors per track */
    u_int16_t	hds;		/* [-h] drive heads */
    u_int32_t	hid;		/* [-o] hidden sectors */
    u_int32_t	bsec;		/* [-s] big total sectors */
};
/* FAT32 extensions */
struct bsxbpb {
    u_int32_t	bspf;		/* [-a] big sectors per FAT */
    u_int16_t	xflg;		/* control flags */
    u_int16_t	vers;		/* file system version */
    u_int32_t	rdcl;		/* root directory start cluster */
    u_int16_t	infs;		/* [-i] file system info sector */
    u_int16_t	bkbs;		/* [-k] backup boot sector */
};
.Ed
.Sh LIMITATION
The maximum file size is 4GB, even if the file system itself is bigger.
.Sh EXIT STATUS
Exit status is 0 on success and 1 on error.
.Sh EXAMPLES
Create a file system, using default parameters, on
.Pa /dev/ad0s1 :
.Bd -literal -offset indent
newfs_msdos /dev/ad0s1
.Ed
.Pp
Create a standard 1.44M file system, with volume label
.Ar foo ,
on
.Pa /dev/fd0 :
.Bd -literal -offset indent
newfs_msdos -f 1440 -L foo fd0
.Ed
.Pp
Create a 30MB image file, with the FAT partition starting
63 sectors within the image file:
.Bd -literal -offset indent
newfs_msdos -C 30M -@63s ./somefile
.Ed
.Sh SEE ALSO
.Xr disktab 5 ,
.Xr disklabel 8 ,
.Xr fdisk 8 ,
.Xr newfs 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 3.0 .
.Sh AUTHORS
.An Robert Nordier Aq rnordier@FreeBSD.org .