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FD(4)                      Linux Programmer's Manual                     FD(4)



NAME
       fd - floppy disk device

CONFIGURATION
       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, combination 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 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

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

       FDCLRPRM
              clears the media information of a drive (geometry of disk in drive).

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

       FDDEFPRM
              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.

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

       FDFLUSH
              invalidates the buffer cache for the given drive.

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

       FDSETMAXERRS
              gets the current error thresholds.

       FDGETDRVTYP
              gets the internal name of the drive.

       FDWERRORCLR
              clears the write error statistics.

       FDWERRORGET
              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.

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

       FDSETDRVPRM
              sets various drive parameters.

       FDGETDRVPRM
              reads these parameters back.

       FDGETDRVSTAT
              gets the cached drive state (disk changed, write protected et al.)

       FDPOLLDRVSTAT
              polls the drive and return its state.

       FDGETFDCSTAT
              gets the floppy controller state.

       FDRESET
              resets the floppy controller under certain conditions.

       FDRAWCMD
              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 floppycontrol.

FILES
       /dev/fd*

NOTES
       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  pre-
       vent  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.

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

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             1995-01-29                             FD(4)