a76d855399
Add references to ATAPI support; do a quick job from UTSL on scanners, and the changer thing. Also document that SCSI bus Ethernet interface that appears to be supported. Clean up some nroff stuff in the exiting pages.
384 lines
12 KiB
Groff
384 lines
12 KiB
Groff
.\" $NetBSD: st.4,v 1.8 1998/06/10 11:15:20 fair Exp $
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.\"
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.\" Copyright (c) 1996
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.\" Julian Elischer <julian@freebsd.org>. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd August 23, 1996
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.Dt ST 4
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.Os NetBSD
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.Sh NAME
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.Nm st
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.Nd SCSI tape driver
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.Sh SYNOPSIS
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.Cd st* at scsibus? target ? lun ?
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.Cd st1 at scsibus0 target 4 lun 0
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for
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.Tn SCSI
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tape drives.
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It allows a tape drive to be run in several different
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modes depending on minor numbers and supports several different
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.Sq sub-modes .
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The device can have both a
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.Em raw
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interface and a
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.Em block
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interface; however, only the raw interface is usually used (or recommended).
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.Pp
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.Tn SCSI
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devices have a relatively high level interface and talk to the system via a
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.Tn SCSI
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adapter and a
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.Tn SCSI
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adapter driver
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(e.g.
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.Xr ahc 4 ) .
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A
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.Tn SCSI
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adapter must also be separately configured into the system before a
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.Tn SCSI
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tape can be configured.
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.Pp
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As the
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.Tn SCSI
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adapter is probed during boot, the
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.Tn SCSI
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bus is scanned for devices.
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Any devices found which answer as
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.Sq Em Sequential
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type devices will be attached to the
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.Nm
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driver.
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.Sh MOUNT SESSIONS
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The
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.Nm
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driver is based around the concept of a
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.Dq Em mount session ,
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which is defined as the period between the time that a tape is
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mounted, and the time when it is unmounted.
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Any parameters set during a mount session remain in effect for the
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remainder of the session or until replaced.
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The tape can be unmounted, bringing the session to a close in
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several ways.
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These include:
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.Bl -enum
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.It
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Closing an
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.Sq unmount device ,
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referred to as sub-mode 00 below.
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An example is
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.Pa /dev/rst0 .
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.It
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Using the
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.Dv MTOFFL
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.Xr ioctl 2
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command, reachable through the
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.Sq Cm offline
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command of
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.Xr mt 1 .
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.It
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Opening a different mode will implicitly unmount the tape, thereby
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closing off the mode that was previously mounted.
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All parameters will be loaded freshly from the new mode
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(See below for more on modes).
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.El
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.Sh MODES AND SUB-MODES
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There are several different
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.Sq operation
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modes.
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These are controlled by bits 2 and 3 of the minor number
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and are designed to allow users to easily read and write different
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formats of tape on devices that allow multiple formats.
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The parameters for each mode can be set individually by hand with the
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.Xr mt 1
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command.
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When a device corresponding to a particular mode is first
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mounted, The operating parameters for that mount session are copied
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from that mode.
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Further changes to the parameters during the session will change
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those in effect for the session but not those set in the operation mode.
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To change the parameters for an operation mode, one must compile
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them into the
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.Dq Em quirk
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table in the driver's source code.
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.Pp
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In addition to the operating modes mentioned above, bits 0 and 1
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of the minor number are interpreted as
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.Sq sub-modes .
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The sub-modes differ in the action taken when the device is closed:
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.Bl -tag -width XXXX
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.It 00
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A close will rewind the device; if the tape has been written, then
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a file mark will be written before the rewind is requested.
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The device is unmounted.
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.It 01
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A close will leave the tape mounted.
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If the tape was written to, a file mark will be written.
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No other head positioning takes place.
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Any further reads or writes will occur directly after the last
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read, or the written file mark.
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.It 10
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A close will rewind the device.
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If the tape has been written, then a file mark will be written
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before the rewind is requested.
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On completion of the rewind an unload command will be issued.
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The device is unmounted.
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.It 11
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Reserved.
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Currently unused.
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.El
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.Sh BLOCKING MODES
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.Tn SCSI
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tapes may run in either
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.Sq Em variable
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or
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.Sq Em fixed
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block-size modes.
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Most
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.Tn QIC Ns -type
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devices run in fixed block-size mode, where most nine-track tapes
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and many new cartridge formats allow variable block-size.
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The difference between the two is as follows:
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.Bl -inset
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.It Variable block-size:
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Each write made to the device results in a single logical record
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written to the tape.
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One can never read or write
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.Em part
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of a record from tape (though you may request a larger block and
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read a smaller record); nor can one read multiple blocks.
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Data from a single write is therefore read by a single read.
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The block size used may be any value supported by the device, the
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.Tn SCSI
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adapter and the system (usually between 1 byte and 64 Kbytes,
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sometimes more).
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.Pp
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When reading a variable record/block from the tape, the head is
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logically considered to be immediately after the last item read,
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and before the next item after that.
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If the next item is a file mark, but it was never read, then the
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next process to read will immediately hit the file mark and receive
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an end-of-file notification.
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.It Fixed block-size
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Data written by the user is passed to the tape as a succession of
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fixed size blocks.
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It may be contiguous in memory, but it is considered to be a series
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of independent blocks.
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One may never write an amount of data that is not an exact multiple
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of the blocksize.
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One may read and write the same data as a different set of records,
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In other words, blocks that were written together may be read
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separately, and vice-versa.
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.Pp
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If one requests more blocks than remain in the file, the drive will
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encounter the file mark.
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Because there is some data to return (unless there were no records
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before the file mark), the read will succeed, returning that data.
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The next read will return immediately with an EOF (as above, if
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the file mark is never read, it remains for the next process to
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read if in no-rewind mode).
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.El
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.Sh FILE MARK HANDLING
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The handling of file marks on write is automatic.
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If the user has written to the tape, and has not done a read since
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the last write, then a file mark will be written to the tape when
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the device is closed.
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If a rewind is requested after a write, then the driver assumes
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that the last file on the tape has been written, and ensures that
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there are two file marks written to the tape.
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The exception to this is that there seems to be a standard (which
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we follow, but don't understand why) that certain types of tape do
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not actually write two file marks to tape, but when read, report a
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.Sq phantom
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file mark when the last file is read.
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These devices include the QIC family of devices
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(it might be that this set of devices is
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the same set as that of fixed block devices.
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This has not been determined yet, and they are treated as separate
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behaviors by the driver at this time).
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.Sh KERNEL CONFIGURATION
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Because different tape drives behave differently, there is a
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mechanism within the source to
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.Nm
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to quickly and conveniently recognize and deal with brands and
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models of drive that have special requirements.
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.Pp
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There is a table (called the
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.Dq Em quirk table )
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in which the identification strings of known errant drives can be stored.
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Alongside each is a set of flags that allows the setting
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of densities and blocksizes for each of the modes, along with a
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set of `QUIRK' flags that can be used to enable or disable sections
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of code within the driver if a particular drive is recognized.
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.Sh IOCTLS
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The following
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.Xr ioctl 2
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calls apply to
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.Tn SCSI
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tapes.
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Some also apply to other tapes.
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They are defined in the header file
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.Aq Pa sys/mtio.h .
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.\"
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.\" Almost all of this discussion belongs in a separate mt(4)
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.\" manual page, since it is common to all magnetic tapes.
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.\"
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.Pp
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.Bl -tag -width MTIOCEEOT
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.It Dv MTIOCGET
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.Pq Li "struct mtget"
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Retrieve the status and parameters of the tape.
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.It Dv MTIOCTOP
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.Pq Li "struct mtop"
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Perform a multiplexed operation.
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The argument structure is as follows:
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.Bd -literal -offset indent
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struct mtop {
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short mt_op;
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daddr_t mt_count;
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};
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.Ed
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.Pp
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The following operation values are defined for
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.Va mt_op :
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.Bl -tag -width MTSELDNSTY
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.It Dv MTWEOF
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Write
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.Va mt_count
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end of file marks at the present head position.
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.It Dv MTFSF
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Skip over
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.Va mt_count
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file marks.
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Leave the head on the EOM side of the last skipped file mark.
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.It Dv MTBSF
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Skip
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.Em backwards
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over
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.Va mt_count
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file marks.
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Leave the head on the BOM (beginning of media)
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side of the last skipped file mark.
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.It Dv MTFSR
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Skip forwards over
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.Va mt_count
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records.
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.It Dv MTBSR
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Skip backwards over
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.Va mt_count
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records.
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.It Dv MTREW
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Rewind the device to the beginning of the media.
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.It Dv MTOFFL
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Rewind the media (and, if possible, eject).
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Even if the device cannot eject the media it will often no longer
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respond to normal requests.
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.It Dv MTNOP
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No-op; set status only.
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.It Dv MTERASE
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Erase the media from current position. If the field
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.Va mt_count
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is nonzero, a full erase is done (from current position to end of
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media). If
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.Va mt_count
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is zero, only an erase gap is written. It is hard to say which
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drives support only one but not the other option
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.It Dv MTCACHE
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Enable controller buffering.
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.It Dv MTNOCACHE
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Disable controller buffering.
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.It Dv MTSETBSIZ
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Set the blocksize to use for the device/mode.
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If the device is capable of variable blocksize operation, and the
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blocksize is set to 0, then the drive will be driven in variable mode.
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This parameter is in effect for the present mount session only.
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.It Dv MTSETDNSTY
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Set the density value (see
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.Xr mt 1 )
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to use when running in the mode opened (minor bits 2 and 3).
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This parameter is in effect for the present
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mount session only.
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.It Dv MTCMPRESS
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Enable or disable tape drive data compression.
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Typically tape drives will quite contentedly ignore settings on
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reads, and will probably keep you from changing density for writing
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anywhere but BOT.
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.El
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.It Dv MTIOCIEOT
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Set end-of-tape processing (not presently supported for
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.Nm
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devices).
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.It Dv MTIOCEEOT
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Set end-of-tape processing (not presently supported for
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.Nm
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devices).
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.It Dv MTIOCRDSPOS
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.Pq Li "u_int32_t"
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Read device logical block position.
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Not all drives support this option.
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.It Dv MTIOCRDHPOS
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.Pq Li "u_int32_t"
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Read device hardware block position.
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Not all drives support this option.
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.It Dv MTIOCSLOCATE
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.Pq Li "u_int32_t"
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Position the tape to the specified device logical block position.
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.It Dv MTIOCHLOCATE
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.Pq Li "u_int32_t"
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Position the tape to the specified hardware block position.
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Not all drives support this option.
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.El
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.Sh FILES
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.Bl -tag -width /dev/[n][e]rst[0-9] -compact
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.It Pa /dev/[n][e]rst[0-9]
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general form:
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.It Pa /dev/rst0
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Mode 0, rewind on close
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.It Pa /dev/nrst0
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Mode 2, No rewind on close
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.It Pa /dev/erst0
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Mode 3, Eject on close (if capable)
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.El
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.Sh DIAGNOSTICS
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None.
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.Sh SEE ALSO
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.Xr mt 1 ,
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.Xr intro 4 ,
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.Xr mtio 4 ,
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.Xr scsi 4
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.Sh HISTORY
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This
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.Nm
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driver was originally written for
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.Tn Mach
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2.5 by Julian Elischer, and was ported to
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.Nx
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by Charles Hannum.
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This man page was edited for
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.Nx
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by Jon Buller.
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