dds2index(1) General Commands Manual dds2index(1)NAME
dds2index - tool to create an indexfile for the use of
SYNOPSIS
dds2index [options]
DESCRIPTION
dds2index creates an index file that is required by the file extraction utility dds2tar(1). It works on tar archives stored on dds tape
devices (DAT). Since the file structure of the tape archives is used to extract the files, the archive must be an uncompressed tar ar-
chive. But compression by the transparent signal processor of the tape device is allowed.
The index created by dds2index is written to stdout by default and should normally be stored on hard disk as indexfile for later use by
dds2tar(1).
The default tape device to read from is /dev/nst0, which may be overridden with the environment variable TAPE, which in turn may be over-
ridden with the -f device option. The device must be a SCSI tape device.
OPTIONS -f devicefile
device of the tape archive. Must be a character special file.
-t indexfile
write the index to indexfile, not to stdout.
-z,--compress
write the index in (gzip) compressed mode.
--help print some screens of online help with examples through a pager and exit immediatley.
OPTIONS you didn't really need-b, --block-size
Set the maximal blocksize, dds2index can handle.
--z, --no-compress
Don't filter the archive file through gzip.
-v,--verbose
verbose mode. Print to stderr what is going on.
-h,--hash-mode
Print a hash sign '#' to stderr for each MB read from tape.
-V,--version
Print the version number of dds2index to stderr and exit immediately.
EXAMPLES
Example of getting the index from the default tape /dev/nst0 and storing it in file archive.idx:
dds2index -v -t archive.idx
WARNING
This program can only read records (tar is calling them tape blocks) up to 32 kbytes. A bigger buffer will cause problems with the Linux
device driver.
ENVIRONMENT
The environment variable TAPE overrides the default tape device /dev/nst0.
FILES
/dev/nst0 default tape device file. Must be a character special file.
SEE ALSO dds2tar(1), mt(1), mt-dds(1), tar(1), gzip(1)HISTORY
This program was created as a tool for dds2tar(1).
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 dds2index(1)
Check Out this Related Man Page
MTIO(4) BSD Kernel Interfaces Manual MTIO(4)NAME
mtio -- generic magnetic tape I/O interface
SYNOPSIS
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/mtio.h>
DESCRIPTION
Magnetic tape has been the computer system backup and data transfer medium of choice for decades, because it has historically been cheaper in
cost per bit stored, and the formats have been designed for portability and storage. However, tape drives have generally been the slowest
mass storage devices attached to any computer system.
Magnetic tape comes in a wide variety of formats, from classic 9-track, through various Quarter Inch Cartridge (QIC) variants, to more modern
systems using 8mm video tape, and Digital Audio Tape (DAT). There have also been a variety of proprietary tape systems, including DECtape,
and IBM 3480.
UNIX TAPE I/O
Regardless of the specific characteristics of the particular tape transport mechanism (tape drive), UNIX tape I/O has two interfaces: "block"
and "raw". I/O through the block interface of a tape device is similar to I/O through the block special device for a disk driver: the indi-
vidual read(2) and write(2) calls can be done in any amount of bytes, but all data is buffered through the system buffer cache, and I/O to
the device is done in 1024 byte sized blocks. This limitation is sufficiently restrictive that the block interface to tape devices is rarely
used.
The "raw" interface differs in that all I/O can be done in arbitrary sized blocks, within the limitations for the specific device and device
driver, and all I/O is synchronous. This is the most flexible interface, but since there is very little that is handled automatically by the
kernel, user programs must implement specific magnetic tape handling routines, which puts the onus of correctness on the application program-
mer.
DEVICE NAME CONVENTIONS
Each magnetic tape subsystem has a couple of special devices associated with it.
The block device is usually named for the driver, e.g. /dev/st0 for unit zero of a st(4) SCSI tape drive.
The raw device name is the block device name with an "r" prepended, e.g. /dev/rst0.
By default, the tape driver will rewind the tape drive when the device is closed. To make it possible for multiple program invocations to
sequentially write multiple files on the same tape, a "no rewind on close" device is provided, denoted by the letter "n" prepended to the
name of the device, e.g. /dev/nst0, /dev/nrst0.
The mt(1) command can be used to explicitly rewind, or otherwise position a tape at a particular point with the no-rewind device.
FILE MARK HANDLING
Two end-of-file (EOF) markers mark the end of a tape (EOT), and one end-of-file marker marks the end of a tape file.
By default, the tape driver will write two End Of File (EOF) marks and rewind the tape when the device is closed after the last write.
If the tape is not to be rewound it is positioned with the head in between the two tape marks, where the next write will over write the sec-
ond end-of-file marker.
All of the magnetic tape devices may be manipulated with the mt(1) command.
A number of ioctl(2) operations are available on raw magnetic tape. Please see <sys/mtio.h> for their definitions.
The manual pages for specific tape device drivers should list their particular capabilities and limitations.
SEE ALSO dd(1), mt(1), pax(1), tar(1), st(4), wt(4)HISTORY
The mtio manual appeared in 4.2BSD.
BUGS
The status should be returned in a device independent format.
If and when NetBSD is updated to deal with non-512 byte per sector disk media through the system buffer cache, perhaps a more sane tape
interface can be implemented.
BSD January 14, 1999 BSD