fd(4) — Linux manual page

NAME | CONFIGURATION | DESCRIPTION | FILES | NOTES | SEE ALSO | COLOPHON

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

NAME         top

       fd - floppy disk device

CONFIGURATION         top

       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         Capacity   Cyl.   Sect.   Heads    Base
                      KiB                             minor #
       ───────────────────────────────────────────────────────
       fdnd360        360       40      9       2        4

       5.25 inch high-density device files:

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

       3.5 inch double-density device files:

       Name         Capacity   Cyl.   Sect.   Heads    Base
                      KiB                             minor #
       ───────────────────────────────────────────────────────
       fdnu360        360       80      9       1       12
       fdnu720        720       80      9       2       16
       fdnu800        800       80     10       2       120

       fdnu1040       1040      80     13       2       84
       fdnu1120       1120      80     14       2       88

       3.5 inch high-density device files:

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

       3.5 inch extra-density device files:

       Name         Capacity   Cyl.   Sect.   Heads    Base
                      KiB                             minor #
       ───────────────────────────────────────────────────────
       fdnu2880       2880      80     36       2       32
       fdnCompaQ      2880      80     36       2       36
       fdnu3200       3200      80     40       2       104
       fdnu3520       3520      80     44       2       108
       fdnu3840       3840      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:

       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 reenable autodetection, you have to issue an
              FDCLRPRM.

       FDGETDRVTYP
              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.

       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 floppycontrol(1)
       manual page.

FILES         top

       /dev/fd*

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 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         top

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

COLOPHON         top

       This page is part of release 5.10 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
       https://www.kernel.org/doc/man-pages/.

Linux                          2020-08-13                          FD(4)

Pages that refer to this page: fdformat(8)