mt - magnetic tape control

     mt [-f device] [count]

     Mt is a user  interface  to  the  magnetic  tape  commands  described  in
     mtio(4).   It allows one to space a tape forwards or backwards, write end
     of file markers, etc.

     With the -f option a tape device can be named, otherwise the  environment
     variable TAPE is used if set.  Standard input is used if the tape name is
     a dash (-).  The count argument is used to tell how many blocks or  files
     to space or how many file markers to write.  It may be a C-style decimal,
     octal or hexadecimal constant, by default "1".

     Command is the action to perform, it may be one of the following, or  any
     unambiguous prefix (like st for status):

     eof, weof      Write count end-of-file markers.

     fsf            Forward space count file markers.

     fsr            Forward space  count  records.   (The  size  of  a  record
                    depends  on  the tape, and may even be variable, depending
                    on the size of the writes.)

     bsf            Backwards space count files.  The count  may  be  zero  to
                    backspace  to  the  start  of  the  current file.  (A tape
                    device need not support backwards movement, or may be very
                    slow  doing  it.   Rewinding  and  forward  spacing may be

     bsr            Backwards space count records.   The  tape  is  positioned
                    after  the  last  block  of the previous file if you hit a
                    filemark when spacing backwards.  The block count  is  set
                    to  -1 to indicate that the driver has no idea where it is
                    on the previous file.

     eom            Forward space to the end of media.

     rewind         Rewind the tape.

     offline, rewoffl
                    Rewind and take offline.  This may cause  some  drives  to
                    eject the tape.

     status         Shows the status of the drive, the sense key of  the  last
                    SCSI  error,  current  file number, current record number,
                    residual count if the last command that  encountered  end-
                    of-file, and the current block size.

     retension      Removes tape tension by winding  and  rewinding  the  tape

     erase          Erases the tape completely and rewinds it.

     density        Sets the density code to read or write the tape to  count.
                    Density codes supported depend on the drive.  This command
                    need not be used if the drive senses the proper density on
                    read and can only write one density.

     blksize, blocksize
                    Sets the block size used to read  or  write  the  tape  to
                    count.   This  command may be used to select a fixed block
                    size for a variable block size tape.  This will  speed  up
                    I/O  for  small  block  sizes.   Use  a  zero count to use
                    variable sized blocks again.


     TAPE           Tape drive to use if set.


     /dev/nrst4     Default tape device.

     mtio(4), st(4).

     Kees J. Bot (