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 (i.e.,  user  root,  group  floppy)  and  have
       either  mode  0660  (access checking via group membership) or mode 0666
       (everybody has access). The minor numbers encode the device type, drive
       number, and controller number.  For each device type (that is, combina-
       tion of density and track count) there is a base minor number.  To this
       base  number,  add  the drive's number on its controller and 128 if the
       drive is on the secondary controller. In the following device tables, n
       represents the drive number.

       Warning:  If  you  use  formats with more tracks than supported by your
       drive, you may cause it mechanical damage.  Trying once if more  tracks
       than  the  usual  40/80 are supported should not damage it, but no war-
       ranty 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  fol-
       lowing 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  for-

              invalidates the buffer cache for the given drive.

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

              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 floppy-

       The various formats allow to read and write many types of disks.   How-
       ever,  if a floppy is formatted with a too small inter sector gap, per-
       formance 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).  Read-
       ing 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  (,  David  Niemi  (,
       Bill Broadhurst (

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

Linux                             1995-01-29                             FD(4)