FD(4)                            Special files                           FD(4)

       fd - floppy disk device

       Floppy drives are block devices with major number 2.  Typically they
       are owned by root.floppy and have either mode 0660 (access checking via
       group membership) or mode 0666 (everybody has access).  For the
       following devices, n is the drive number.  It is 0 for the first drive,
       1 for the second etc.  To get a minor number for a specific drive
       connected to the first controller, add n to the minor base number.  If
       it is connected to the second controller, add n+128 to the minor base
       number.  Warning: If you use formats with more tracks than supported by
       your drive, you may damage it mechanically.  Trying once if more tracks
       than the usual 40/80 are supported should not damage it, but no
       warranty is given for that.  Don't create device entries for those
       formats to prevent their usage if you are not sure.

       Drive independent device files which automatically detect the media
       format and capacity:

       Name   Base minor #
       fdn    0

       5.25 inch double density device files:

       Name         Capac.   Cyl.   Sect.   Heads   Base minor #
       fdnd360      360K     40     9       2       4

       5.25 inch high density device files:

       Name         Capac.   Cyl.   Sect.   Heads   Base minor #
       fdnh360      360K     40     9       2       20
       fdnh410      410K     41     10      2       48
       fdnh420      420K     42     10      2       64
       fdnh720      720K     80     9       2       24
       fdnh880      880K     80     11      2       80
       fdnh1200     1200K    80     15      2       8
       fdnh1440     1440K    80     18      2       40
       fdnh1476     1476K    82     18      2       56
       fdnh1494     1494K    83     18      2       72
       fdnh1600     1600K    80     20      2       92

       3.5 inch double density device files:

       Name         Capac.   Cyl.   Sect.   Heads   Base minor #
       fdnD360      360K     80     9       1       12
       fdnD720      720K     80     9       2       16
       fdnD800      800K     80     10      2       120
       fdnD1040     1040K    80     13      2       84
       fdnD1120     1120K    80     14      2       88

       3.5 inch high density device files:

       Name         Capac.   Cyl.   Sect.   Heads   Base minor #
       fdnH360      360K     40     9       2       12
       fdnH720      720K     80     9       2       16

       fdnH820      820K     82     10      2       52
       fdnH830      830K     83     10      2       68
       fdnH1440     1440K    80     18      2       28
       fdnH1600     1600K    80     20      2       124
       fdnH1680     1680K    80     21      2       44
       fdnH1722     1722K    82     21      2       60
       fdnH1743     1743K    83     21      2       76
       fdnH1760     1760K    80     22      2       96
       fdnH1840     1840K    80     23      2       116
       fdnH1920     1920K    80     24      2       100

       3.5 inch extra density device files:

       Name         Capac.   Cyl.   Sect.   Heads   Base minor #
       fdnE2880     2880K    80     36      2       32
       fdnCompaQ    2880K    80     36      2       36
       fdnE3200     3200K    80     40      2       104
       fdnE3520     3520K    80     44      2       108
       fdnE3840     3840K    80     48      2       112

       fd special files access the floppy disk drives in raw mode.  The
       following ioctl(2) calls are supported by fd devices:

              clears the media information of a drive (geometry of disk in

              sets the media information of a drive. The media information
              will be lost when the media is changed.

              sets the media information of a drive (geometry of disk in
              drive). The media information will not be lost when the media is
              changed. This will disable autodetection. In order to re-enable
              autodetection, you have to issue an FDCLRPRM .

              returns the type of a drive (name parameter).  For formats which
              work in several drive types, FDGETDRVTYP returns a name which is
              appropriate for the oldest drive type which supports this

              invalidates the buffer cache for the given drive.

              sets the error thresholds for reporting errors, aborting the
              operation, recalibrating, resetting, and reading sector by

              gets the current error thresholds.

              gets the internal name of the drive.

              clears the write error statistics.

              reads the write error statistics. These include the total number
              of write errors, the location and disk of the first write error,
              and the location and disk of the last write error. Disks are
              identified by a generation number which is incremented at
              (almost) each disk change.

              Switch the drive motor off for a few microseconds. This might be
              needed in order to access a disk whose sectors are too close

              sets various drive parameters.

              reads these parameters back.

              gets the cached drive state (disk changed, write protected et

              polls the drive and return its state.

              gets the floppy controller state.

              resets the floppy controller under certain conditions.

              sends a raw command to the floppy controller.

       For more precise information, consult also the <linux/fd.h> and
       <linux/fdreg.h> include files, as well as the manual page for

       The various formats allow to read and write many types of disks.
       However, if a floppy is formatted with a too small inter sector gap,
       performance may drop, up to needing a few seconds to access an entire
       track. To prevent this, use interleaved formats. It is not possible to
       read floppies which are formatted using GCR (group code recording),
       which is used by Apple II and Macintosh computers (800k disks).
       Reading floppies which are hard sectored (one hole per sector, with the
       index hole being a little skewed) is not supported.  This used to be
       common with older 8 inch floppies.


       Alain Knaff (Alain.Knaff@inrialpes.fr), David Niemi
       (niemidc@erols.com), Bill Broadhurst (bbroad@netcom.com).

       floppycontrol(1), mknod(1), chown(1), getfdprm(1), superformat(1),
       mount(8), setfdprm(8)

Linux                          January 29, 1995                          FD(4)