NEWFS_MSDOS(8)          NetBSD System Manager's Manual          NEWFS_MSDOS(8)

     newfs_msdos -- construct a new MS-DOS (FAT) file system

     newfs_msdos [-N] [-B boot] [-F FAT-type] [-I volid] [-L label] [-O OEM]
                 [-S sector-size] [-a FAT-size] [-b block-size]
                 [-c cluster-size] [-e dirents] [-f format] [-h heads]
                 [-i info] [-k backup] [-m media] [-n FATs] [-o hidden]
                 [-r reserved] [-s total] [-u track-size] special [disktype]

     The newfs_msdos utility creates a FAT12, FAT16, or FAT32 file system on
     device special, using disktab(5) entry disktype to determine geometry, if

     The options are as follow:

     -N      Don't create a file system: just print out parameters.

     -B boot
             Get bootstrap from file.

     -F FAT-type
             FAT type (one of 12, 16, or 32).

     -I volid
             Volume ID.

     -L label
             Volume label (up to 11 characters).  The label should consist of
             only those characters permitted in regular DOS (8+3) filenames.
             The default is "NO_NAME".

     -O OEM  OEM string (up to 8 characters).  The default is "NetBSD".

     -S sector-size
             Number of bytes per sector.  Acceptable values are powers of 2 in
             the range 512 through 32768.

     -a FAT-size
             Number of sectors per FAT.

     -b block-size
             File system block size (bytes per cluster).  This should resolve
             to an acceptable number of sectors per cluster (see below).

     -c cluster-size
             Sectors per cluster.  Acceptable values are powers of 2 in the
             range 1 through 128.

     -e dirents
             Number of root directory entries (FAT12 and FAT16 only).

     -f format
             Specify a standard (floppy disk) format.  The standard formats
             are (capacities in kilobytes): 160, 180, 320, 360, 640, 720,
             1200, 1232, 1440, 2880.

     -h heads
             Number of drive heads.

     -i info
             Location of the file system info sector (FAT32 only).  A value of
             0xffff signifies no info sector.

     -k backup
             Location of the backup boot sector (FAT32 only).  A value of
             0xffff signifies no backup sector.

     -m media
             Media descriptor (acceptable range 0xf0 to 0xff).

     -n FATs
             Number of FATs.  Acceptable values are 1 to 16 inclusive.  The
             default is 2.

     -o hidden
             Number of hidden sectors.

     -r reserved
             Number of reserved sectors.

     -s total
             File system size.

     -u track-size
             Number of sectors per track.

     If newfs_msdos receives a SIGINFO signal (see the status argument for
     stty(1)), a line will be written to the standard error output indicating
     the name of the device currently being formatted, the sector number being
     written, and the total number of sectors to be written.

     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.

     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 */

           newfs_msdos /dev/rwd1a

     Create a file system, using default parameters, on /dev/rwd1a.

           newfs_msdos -f 1440 -L foo /dev/rfd0a

     Create a standard 1.44M file system, with volume label foo, on

     Exit status is 0 on success and 1 on error.

     disktab(5), disklabel(8), fdisk(8), newfs(8)

     The newfs_msdos command first appeared in NetBSD 1.3.

     Robert Nordier <>.

NetBSD 5.1                     November 25, 2006                    NetBSD 5.1

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