.\"	$NetBSD: xbd.4,v 1.4 2014/03/18 18:20:39 riastradh Exp $
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.\" by Jean-Yves Migeon <jym@NetBSD.org>.
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.Dd January 8, 2011
.Dt XBD 4 xen
.Os
.Sh NAME
.Nm xbd
.Nd Xen frontend paravirtualized block device interface
.Sh SYNOPSIS
.Cd "xbd* at xenbus?"
.Sh DESCRIPTION
The
.Nm
interface forms the frontend part of the paravirtualized drivers
used by
.Tn Xen
guest domains to have a block device interface.
.Pp
From a guest point of view,
.Nm
is similar to a hard disk, and can be treated in the very same way
regarding partitioning, file systems creation and usage, and mounting.
By default, a
.Nx
guest domain will assume that
.Dq xbd0a
serves as the root file system.
.Pp
When the host is
.Nx ,
the
.Nm
interface is backed by a
.Xr xbdback 4
interface.
In the XenStore,
.Nm xbd
and
.Nm xbdback
are identified by
.Dq vbd
(virtual block device)
entries.
.Sh DIAGNOSTICS
.Bl -diag
.It "xbd%d: using event channel %d"
Specifies the event channel used by this
.Nm
interface.
.It "xbd%d: %s MB, %d bytes/sect x %u sectors"
Gives the total size of the
.Nm
block device, its sector size and total number of sectors.
.It "xbd%d: WARNING: cache flush not supported by backend"
The backend driver associated with this
.Nm
device does not support cache flushing operation.
This can be problematic for file system operations that require
cache sync to avoid data loss or corruption.
.El
.Sh SEE ALSO
.Xr xbdback 4 ,
.Xr xenbus 4 ,
.Xr dkctl 8
.Sh HISTORY
The
.Nm
driver first appeared in
.Nx 3.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Manuel Bouyer Aq Mt bouyer@NetBSD.org .