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)