# fd

## 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.  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 #
           ───────────────
           **fd** _n_       0
    
           5.25 inch double-density device files:
           Name         Capacity   Cyl.   Sect.   Heads    Base
                          KiB                             minor #
           ───────────────────────────────────────────────────────
           **fd** _n_**d360** 360       40      9       2        4
    
           5.25 inch high-density device files:
           Name         Capacity   Cyl.   Sect.   Heads    Base
                          KiB                             minor #
           ───────────────────────────────────────────────────────
           **fd** _n_**h360** 360       40      9       2       20
           **fd** _n_**h410** 410       41     10       2       48
           **fd** _n_**h420** 420       42     10       2       64
           **fd** _n_**h720** 720       80      9       2       24
           **fd** _n_**h880** 880       80     11       2       80
           **fd** _n_**h1200** 1200      80     15       2        8
           **fd** _n_**h1440** 1440      80     18       2       40
           **fd** _n_**h1476** 1476      82     18       2       56
           **fd** _n_**h1494** 1494      83     18       2       72
           **fd** _n_**h1600** 1600      80     20       2       92
    
           3.5 inch double-density device files:
           Name         Capacity   Cyl.   Sect.   Heads    Base
                          KiB                             minor #
           ───────────────────────────────────────────────────────
           **fd** _n_**u360** 360       80      9       1       12
           **fd** _n_**u720** 720       80      9       2       16
           **fd** _n_**u800** 800       80     10       2       120
           **fd** _n_**u1040** 1040      80     13       2       84
           **fd** _n_**u1120** 1120      80     14       2       88
    
           3.5 inch high-density device files:
           Name         Capacity   Cyl.   Sect.   Heads    Base
                          KiB                             minor #
           ───────────────────────────────────────────────────────
           **fd** _n_**u360** 360       40      9       2       12
           **fd** _n_**u720** 720       80      9       2       16
           **fd** _n_**u820** 820       82     10       2       52
           **fd** _n_**u830** 830       83     10       2       68
           **fd** _n_**u1440** 1440      80     18       2       28
           **fd** _n_**u1600** 1600      80     20       2       124
           **fd** _n_**u1680** 1680      80     21       2       44
           **fd** _n_**u1722** 1722      82     21       2       60
           **fd** _n_**u1743** 1743      83     21       2       76
           **fd** _n_**u1760** 1760      80     22       2       96
           **fd** _n_**u1840** 1840      80     23       2       116
           **fd** _n_**u1920** 1920      80     24       2       100
    
           3.5 inch extra-density device files:
           Name         Capacity   Cyl.   Sect.   Heads    Base
                          KiB                             minor #
           ───────────────────────────────────────────────────────
           **fd** _n_**u2880** 2880      80     36       2       32
           **fd** _n_**CompaQ** 2880      80     36       2       36
           **fd** _n_**u3200** 3200      80     40       2       104
           **fd** _n_**u3520** 3520      80     44       2       108
           **fd** _n_**u3840** 3840      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 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



           _/dev/fd*_
    


## NOTES



           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.
    


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