NAME
xbdback —
Xen backend paravirtualized
block device interface
SYNOPSIS
pseudo-device xbdback
DESCRIPTION
The
xbdback interface forms the backend part of the
paravirtualized drivers used by Xen domains to offer a block device interface,
similar to a hard disk.
xbdback interfaces are backed either
by a physical device directly, or an image file mounted through
vnd(4).
All
xbdback interfaces follow the “xbdbackXiY”
naming convention, where ‘X’ represents the guest domain
identifier, and ‘Y’ an arbitrary identifier. This identifier is
usually associated to the device node as seen by the guest using
major(3) and
minor(3) numbers. For example,
identifier “769” (0x301) means major
3 and minor
1, identified as “hda1” under Linux convention.
For
NetBSD, the guest device name specified in the
guest configuration file does not matter, and can be chosen arbitrarily.
A
xbdback interface will appear as a
xbd(4) block device inside a
NetBSD guest domain. In the XenStore,
xbd and
xbdback are identified by
“vbd” (virtual block device) entries.
DIAGNOSTICS
- xbd backend: attach device %s (size %d)
for domain %d
- Gives the device used as xbdback
interface for the given guest domain, and its size, in bytes.
- xbd backend 0x%x for domain %d using
event channel %d, protocol %s
- Gives the backend identifier, guest domain ID, event
channel ID, and protocol used for block level communication.
- xbdback %s: can't VOP_OPEN device 0x%x:
%d
- When this message appears in the system message buffer
with error 16 (
EBUSY
), the device is likely to be
already mounted. It must be unmounted first, as the system will refuse to
open it a second time.
SEE ALSO
vnd(4),
xbd(4),
xenbus(4)
HISTORY
The
xbdback driver first appeared in
NetBSD
4.0.
AUTHORS
The
xbdback driver was written by
Manuel
Bouyer
<
bouyer@NetBSD.org>.