MTIO(1) MachTen Programmer’s Manual MTIO(1)

NAME
mtio - magnetic tape interface

DESCRIPTION
The special files named /dev/rmt0 through /dev/rmt15 and
/dev/nrmt0 through /dev/nrmt11 refer to SCSI Digital Audio
Tape (DAT) devices under MachTen.

MachTen supports up to four DAT drives with logical device
unit numbers assigned according to the drive’s relative
position on the SCSI bus. These devices are raw tape
devices with characteristics according to the following
table:

Operation unit lowest density highest den-
sity

Rewind 0 rmt0 rmt8
Norewind 0 rmt4/nrmt0
rmt12/nrmt8

Rewind 1 rmt1 rmt9
Norewind 1 rmt5/nrmt1
rmt13/nrmt9

Rewind 2 rmt2 rmt10
Norewind 2 rmt6/nrmt2
rmt14/nrmt10

Rewind 3 rmt3 rmt11
Norewind 3 rmt7/nrmt3
rmt15/nrmt11

By default, the rmt0, rmt4, rmt8, rmt12, nrmt0 and nrmt8
devices are configured for the first DAT drive (unit 0) on
your SCSI bus. If you have multiple DAT drives, use the
/dev/MAKEDEV script to create additional rmt*/nrmt*
devices for each additional unit added, for example:

/dev/MAKEDEV mt1

will configure the devices for the second DAT drive on
your SCSI.

The rewind devices automatically rewind when the last
requested read, write or seek has finished, or the end of
the tape has been reached. The letter "n" is prepended to
the name of the no-rewind devices.

MachTen tapes are written in multiples of 1024 byte block
records. Two end-of-file markers mark the end of a tape,
and one end-of-file marker marks the end of a tape file.
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 second end-of-file marker.

All of the magtape devices may be manipulated with the
mt(1) command.

A number of program i/o control operations are available
on raw magnetic tape. Refer to sys/mtio.h.

FILES
/dev/rmt* Raw magnetic tape interface
/dev/nrmt* Non rewinding raw magnetic tape interface