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)