NAME

       mt-dds - tool to control a dds device.

SYNOPSIS

       mt-dds comp-on|comp-off|comp-query|comp-log
       mt-dds < tell|label > [ -b  # ]

DESCRIPTION

       mt-dds controls the compression mode of dds tape devices (DAT).

       mt-dds may also report the current tape position in absolute records (relative to begin of
       tape) in a format that may be used later by dds2tar(1) to access tar archives that are not
       the first file on tape.

       The  default  device  is  /dev/nst0, which may be overridden with the environment variable
       TAPE, which in turn may be overridden with the -f device option.  The  device  must  be  a
       character special file.

OPTIONS

   DDS tape device control options
       comp-on
              Enable the hardware compression mode if supported by the device.

       comp-off
              Disable the compression mode, switch to normal mode.

       comp-query
              Print  to  stderr  if compression mode currently is disabled or enabled.  A 0 means
              compression is disabled, a 1 means compression in enabled.

       comp-log
              Print to stdout four lines of information about transferred  kilobytes  before  and
              after hardware compression from and to the device since initialization.

   dds2tar service functions
       tell   Print  three  lines  with  the  current  tape  position,  a block size value (20 by
              default, may be overridden with -b option) and a block length value (blocksize*512)
              to  stdout.  If this output is redirected to a location file locfile, this file may
              be used by dds2tar(1) to access archives on tape.

       label  If the current tape position is the beginning of an  archive  and  the  archive  is
              labeled,  mt-dds  writes the label to stdout and moves the tape back to the current
              position (or back over the filemark).

       ts     If the current tape position is the beginning of an  archive  and  the  archive  is
              labeled,  mt-dds  writes the timestamp in octal format to stdout and moves the tape
              back to the current position (or back over the filemark).  If you  are  using  only
              one computer, the timestamp can be used as a unique archive identifier.

       -b #   Specify the block size # value that is used as a default for the written value with
              the mt-dds tell command (see above).  Also the internal buffer  size  is  specified
              with  this option which is used to read one block in order to get the block size of
              the current tape block. So specify the block  size  of  the  archive  or  a  larger
              number.

   other options
       -f device
              Device  of  the  tape  archive (default is /dev/nst0).  Must be a character special
              file connected to a dds tape device.

       -V,--version
              Print the version number of mt-dds to stderr and exit immediately.

       --help print some  screens  of  online  help  with  examples  through  a  pager  and  exit
              immediately.

EXAMPLES

       Example 1: checking the compression mode of the default tape device
                 mt-dds comp-query

       Example 2: Write the location information as dds2tar command line options to stdout.
                 mt-dds

ENVIRONMENT

       The environment variable TAPE overrides the default tape device /dev/nst0.

       PAGER  The environment variable PAGER overrides the builtin pager command ("/bin/more") to
              display the output of the --help option.

SEE ALSO

       dds2tar(1), dds2index(1), mt(1), tar(1)

HISTORY

       This program was created to use it in conjunction with dds2tar.

AUTHOR

       J"org Weule  (weule@cs.uni-duesseldorf.de),  Phone  +49  211  751409.   This  software  is
       available at ftp.uni-duesseldorf.de:/pub/unix/apollo

                                               2.4                                      mt-dds(1)