125 lines
3.5 KiB
Groff
125 lines
3.5 KiB
Groff
.\" $NetBSD: xbdback.4,v 1.5 2014/03/18 18:20:39 riastradh Exp $
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.\"
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.\" Copyright (c) 2011 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jean-Yves Migeon <jym@NetBSD.org>.
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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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.\" 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd June 7, 2011
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.Dt XBDBACK 4 xen
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.Os
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.Sh NAME
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.Nm xbdback
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.Nd Xen backend paravirtualized block device interface
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.Sh SYNOPSIS
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.Cd "pseudo-device xbdback"
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.Sh DESCRIPTION
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The
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.Nm
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interface forms the backend part of the paravirtualized drivers
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used by
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.Tn Xen
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domains to offer a block device interface, similar to a hard disk.
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.Nm
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interfaces are backed either by a physical device directly,
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or an image file mounted through
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.Xr vnd 4 .
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.Pp
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All
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.Nm
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interfaces follow the
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.Dq xbdbackXiY
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naming convention, where
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.Sq X
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represents the guest domain identifier, and
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.Sq Y
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an arbitrary identifier.
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This identifier is usually associated to the device node as seen
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by the guest using
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.Xr major 3
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and
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.Xr minor 3
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numbers.
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For example, identifier
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.Do 769 Dc Po 0x301 Pc
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means major
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.Em 3
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and minor
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.Em 1 ,
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identified as
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.Dq hda1
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under Linux convention.
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For
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.Nx ,
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the guest device name specified in the guest configuration file
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does not matter, and can be chosen arbitrarily.
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.Pp
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A
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.Nm
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interface will appear as a
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.Xr xbd 4
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block device inside a
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.Nx
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guest domain.
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In the XenStore,
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.Nm xbd
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and
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.Nm xbdback
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are identified by
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.Dq vbd
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(virtual block device)
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entries.
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.Sh DIAGNOSTICS
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.Bl -diag
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.It "xbd backend: attach device %s (size %d) for domain %d"
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Gives the device used as
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.Nm
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interface for the given guest domain, and its size, in bytes.
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.It "xbd backend 0x%x for domain %d using event channel %d, protocol %s"
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Gives the backend identifier, guest domain ID, event channel ID, and
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protocol used for block level communication.
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.It "xbdback %s: can't VOP_OPEN device 0x%x: %d"
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When this message appears in the system message buffer with error 16
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.Po Er EBUSY Pc ,
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the device is likely to be already mounted.
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It must be unmounted first, as the system will refuse to open
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it a second time.
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.El
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.Sh SEE ALSO
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.Xr vnd 4 ,
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.Xr xbd 4 ,
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.Xr xenbus 4
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.Sh HISTORY
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The
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.Nm
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driver first appeared in
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.Nx 4.0 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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driver was written by
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.An Manuel Bouyer Aq Mt bouyer@NetBSD.org .
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