1.\" $NetBSD: xbdback.4,v 1.5 2014/03/18 18:20:39 riastradh Exp $ 2.\" 3.\" Copyright (c) 2011 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Jean-Yves Migeon <jym@NetBSD.org>. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd June 7, 2011 31.Dt XBDBACK 4 xen 32.Os 33.Sh NAME 34.Nm xbdback 35.Nd Xen backend paravirtualized block device interface 36.Sh SYNOPSIS 37.Cd "pseudo-device xbdback" 38.Sh DESCRIPTION 39The 40.Nm 41interface forms the backend part of the paravirtualized drivers 42used by 43.Tn Xen 44domains to offer a block device interface, similar to a hard disk. 45.Nm 46interfaces are backed either by a physical device directly, 47or an image file mounted through 48.Xr vnd 4 . 49.Pp 50All 51.Nm 52interfaces follow the 53.Dq xbdbackXiY 54naming convention, where 55.Sq X 56represents the guest domain identifier, and 57.Sq Y 58an arbitrary identifier. 59This identifier is usually associated to the device node as seen 60by the guest using 61.Xr major 3 62and 63.Xr minor 3 64numbers. 65For example, identifier 66.Do 769 Dc Po 0x301 Pc 67means major 68.Em 3 69and minor 70.Em 1 , 71identified as 72.Dq hda1 73under Linux convention. 74For 75.Nx , 76the guest device name specified in the guest configuration file 77does not matter, and can be chosen arbitrarily. 78.Pp 79A 80.Nm 81interface will appear as a 82.Xr xbd 4 83block device inside a 84.Nx 85guest domain. 86In the XenStore, 87.Nm xbd 88and 89.Nm xbdback 90are identified by 91.Dq vbd 92(virtual block device) 93entries. 94.Sh DIAGNOSTICS 95.Bl -diag 96.It "xbd backend: attach device %s (size %d) for domain %d" 97Gives the device used as 98.Nm 99interface for the given guest domain, and its size, in bytes. 100.It "xbd backend 0x%x for domain %d using event channel %d, protocol %s" 101Gives the backend identifier, guest domain ID, event channel ID, and 102protocol used for block level communication. 103.It "xbdback %s: can't VOP_OPEN device 0x%x: %d" 104When this message appears in the system message buffer with error 16 105.Po Er EBUSY Pc , 106the device is likely to be already mounted. 107It must be unmounted first, as the system will refuse to open 108it a second time. 109.El 110.Sh SEE ALSO 111.Xr vnd 4 , 112.Xr xbd 4 , 113.Xr xenbus 4 114.Sh HISTORY 115The 116.Nm 117driver first appeared in 118.Nx 4.0 . 119.Sh AUTHORS 120.An -nosplit 121The 122.Nm 123driver was written by 124.An Manuel Bouyer Aq Mt bouyer@NetBSD.org . 125