1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
277 lines
6.2 KiB
Groff
277 lines
6.2 KiB
Groff
.\" 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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.\" $FreeBSD$
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.\"
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.Dd January 18, 1996
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.Dt SD 4
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.Os FreeBSD
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.Sh NAME
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.Nm sd
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.Nd SCSI disk driver
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.Sh SYNOPSIS
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.Cd disk sd
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.Cd disk sd1 at scbus0 target 4 lun 0
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.Sh DESCRIPTION
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The
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.Nm sd
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driver provides support for a
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.Tn SCSI
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disk. It allows the disk
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to be divided up into a set of pseudo devices called
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.Em partitions .
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In general the interfaces are similar to those described by
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.Xr wd 4 .
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.Pp
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Where the
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.Xr wd 4
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device has a fairly low level interface to the system,
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.Tn SCSI
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devices have a much higher level interface and talk to the system via
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a
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.Tn SCSI
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host adapter
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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
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before a
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.Tn SCSI
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disk can be configured.
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.Pp
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When 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. Any devices found which answer as
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.Sq Em Direct
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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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In
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.Tn FreeBSD
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releases prior to 2.1, the first found was attached as
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.Li sd0 ,
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the second
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.Li sd1 ,
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and so on.
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Beginning in
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.Fx 2.1
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it became possible to lock down the assignment of
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devices on the
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.Tn SCSI
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bus to particular units of the
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.Nm
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device; refer to
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.Xr scsi 4
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for details on kernel configuration.
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.Sh PARTITIONING
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The
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.Nm
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driver allows the disk to have two levels of partitioning.
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One layer, called the
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.Dq slice layer ,
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is used to separate the
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.Tn FreeBSD
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areas of the disk from areas used by other operating systems.
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The second layer is the native
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.Bx 4.4
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partitioning scheme,
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.Xr disklabel 5 ,
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which is used to subdivide the
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.Tn FreeBSD
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slices into areas for individual filesystems and swap spaces.
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For more information, see
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.Xr fdisk 8
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and
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.Xr disklabel 8 ,
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respectively.)
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.Pp
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If an uninitialized disk is opened, the slice table will be
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initialized with a fictitious
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.Tn FreeBSD
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slice spanning the entire disk. Similarly, if an uninitialized
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(or
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.No non- Ns Tn FreeBSD )
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slice is opened, its disklabel will be initialized with parameters returned
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by the drive and a single
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.Sq Li c
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partition encompassing the entire slice.
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.Sh KERNEL CONFIGURATION
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It is only necessary to explicitly configure one
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.Nm
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device; data structures are dynamically allocated as disks are found
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on the
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.Tn SCSI
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bus.
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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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disks as well as to other disks. They are defined in the header file
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.Aq Pa disklabel.h .
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.Pp
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.Bl -tag -width DIOCSDINFO
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.It Dv DIOCSBAD
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Usually used to set up a bad-block mapping system on the disk.
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.Tn SCSI
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drive incorporate their own bad-block mapping so this command is not
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implemented.
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.It Dv DIOCGDINFO
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Read, from the kernel, the in-core copy of the disklabel for the
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drive. This may be a fictitious disklabel if the drive has never
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been initialized, in which case it will contain information read
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from the
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.Tn SCSI
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inquiry commands.
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.It Dv DIOCSDINFO
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Give the driver a new disklabel to use. The driver
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.Em will not
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write the new
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disklabel to the disk.
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.It Dv DIOCWLABEL
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Enable or disable the driver's software
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write protect of the disklabel on the disk.
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.It Dv DIOCWDINFO
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Give the driver a new disklabel to use. The driver
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.Em will
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write the new disklabel to the disk.
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.El
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.Pp
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In addition, the
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.Xr scsi 4
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general
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.Fn ioctl
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commands may be used with the
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.Nm
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driver, but only against the
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.Sq Li c
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(whole disk) partition.
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.Sh NOTES
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If a removable device is attached to the
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.Nm
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driver, then the act of changing the media will invalidate the
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disklabel and information held within the kernel. To avoid
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corruption, all accesses to the device will be discarded until there
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are no more open file descriptors referencing the device. During this
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period, all new open attempts will be rejected. When no more open
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file descriptors reference the device, the first next open will load a
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new set of parameters (including disklabel) for the drive.
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.Sh FILES
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.Bl -tag -width /dev/rsdXXXXX -compact
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.It Pa /dev/rsd Ns Ar u
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raw mode
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.Tn SCSI
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disk unit
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.Ar u ,
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accessed as an unpartitioned device
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.Sm off
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.It Pa /dev/sd Ar u Pa s Ar n
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.Sm on
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block mode
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.Tn SCSI
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disk unit
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.Ar u ,
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slice
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.Ar n ,
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accessed as an unpartitioned device
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.Sm off
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.It Pa /dev/rsd Ar u Pa s Ar n
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.Sm on
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raw mode
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.Tn SCSI
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disk unit
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.Ar u ,
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slice
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.ar n ,
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accessed as an unpartitioned device
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.It Pa /dev/sd Ns Ar u Ns Ar p
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block mode
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.Tn SCSI
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disk unit
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.Ar u ,
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first
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.Tn FreeBSD
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slice, partition
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.Ar p
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.It Pa /dev/rsd Ns Ar u Ns Ar p
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raw mode
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.Tn SCSI
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disk unit
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.Ar u ,
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first
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.Tn FreeBSD
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slice, partition
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.Ar p
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.Sm off
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.It Xo
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.Pa /dev/sd
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.Ar u
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.Pa s
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.Ar n
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.Ar p
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.Xc
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.Sm on
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block mode
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.Tn SCSI
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disk unit
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.Ar u ,
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.No Ar n Ns th
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slice, partition
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.Ar p
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.Sm off
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.It Xo
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.Pa /dev/rsd
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.Ar u
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.Pa s
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.Ar n
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.Ar p
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.Xc
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raw mode
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.Tn SCSI
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disk unit
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.Ar u ,
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.No Ar n Ns th
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slice, partition
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.Ar p
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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 wd 4 ,
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.Xr disklabel 5 ,
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.Xr disklabel 8 ,
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.Xr fdisk 8
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.Sh HISTORY
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The
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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, and was ported to
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.Tn FreeBSD
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by Julian Elischer. Support for slices was written by Bruce Evans.
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