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

NAME         top

       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,
       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.  If you are not sure, don't create
       device entries for those formats, so as to prevent their usage.

       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 #
       fdnu360      360K     80     9       1       12
       fdnu720      720K     80     9       2       16
       fdnu800      800K     80     10      2       120
       fdnu1040     1040K    80     13      2       84
       fdnu1120     1120K    80     14      2       88

       3.5 inch high-density device files:

       Name         Capac.   Cyl.   Sect.   Heads   Base minor #
       fdnu360      360K     40     9       2       12
       fdnu720      720K     80     9       2       16
       fdnu820      820K     82     10      2       52
       fdnu830      830K     83     10      2       68
       fdnu1440     1440K    80     18      2       28
       fdnu1600     1600K    80     20      2       124
       fdnu1680     1680K    80     21      2       44
       fdnu1722     1722K    82     21      2       60
       fdnu1743     1743K    83     21      2       76
       fdnu1760     1760K    80     22      2       96
       fdnu1840     1840K    80     23      2       116
       fdnu1920     1920K    80     24      2       100

       3.5 inch extra-density device files:

       Name         Capac.   Cyl.   Sect.   Heads   Base minor #
       fdnu2880     2880K    80     36      2       32
       fdnCompaQ    2880K    80     36      2       36
       fdnu3200     3200K    80     40      2       104
       fdnu3520     3520K    80     44      2       108
       fdnu3840     3840K    80     48      2       112

DESCRIPTION         top

       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
              reenable 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 format.

              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 together.

              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 floppycontrol(1) manual

FILES         top


NOTES         top

       The various formats permit reading and writing many types of disks.
       However, if a floppy is formatted with an inter-sector gap that is
       too small, performance may drop, to the point of needing a few
       seconds to access an entire track.  To prevent this, use interleaved

       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         top

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

COLOPHON         top

       This page is part of release 4.12 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                            2014-05-10                            FD(4)

Pages that refer to this page: fdformat(8)