# mt(1)

## NAME

         mt - magnetic tape control

## SYNOPSIS

         mt [-f device] [count]

## DESCRIPTION

         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, otherwise the default device /dev/nrst4 is
         assumed.  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
                        better.)

         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
                        completely.

         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.

## ENVIRONMENT

         TAPE           Tape drive to use if set.

## FILES

         /dev/nrst4     Default tape device.

## SEE ALSO

         mtio(4), st(4).

## AUTHOR

         Kees J. Bot (kjb@cs.vu.nl)