NetBSD/share/man/man4/vnd.4

.\"	$NetBSD: vnd.4,v 1.13 2005/07/29 19:11:16 xtraeme Exp $
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.Dd July 29, 2005
.Dt VND 4
.Os
.Sh NAME
.Nm vnd
.Nd vnode disk driver
.Sh SYNOPSIS
.Cd "pseudo-device vnd" Op Ar count
.Cd "options VND_COMPRESSION
.Sh DESCRIPTION
The
.Nm
driver provides a disk-like interface to a file.
This is useful for a variety of applications, including swap files
and building miniroot or floppy disk images.
.Pp
This document assumes that you're familiar with how to generate kernels,
how to properly configure disks and pseudo-devices in a kernel
configuration file.
.Pp
In order to compile in support for the vnd, you must add a line similar
to the following to your kernel configuration file:
.Bd -unfilled -offset indent
pseudo-device	vnd	4	# vnode disk driver
.Ed
.Pp
The
.Ar count
argument is how many
.Nm vnd Ns s
memory is allocated for at boot time.
In this example, no more than 4
.Nm vnd Ns s
may be configured.
To also compile in support for reading compressed disk images,
add the following option to your kernel config file:
.Bd -unfilled -offset indent
options        VND_COMPRESSION    # compressed vnd(4)
.Ed
.Pp
Compressed disk images are expected in the cloop2 format,
they can be created from "normal" disk images by the
.Xr vndcompress 1
program.
.Pp
There is a run-time utility that is used for configuring
both compressed and uncompressed
.Nm vnd Ns s .
See
.Xr vnconfig 8
for more information.
.Sh FILES
.Bl -tag -width /dev/XXrXvndX -compact
.It Pa /dev/{,r}vnd*
vnd device special files.
.El
.Sh SEE ALSO
.Xr config 1 ,
.Xr vndcompress 1 ,
.Xr MAKEDEV 8 ,
.Xr fsck 8 ,
.Xr mount 8 ,
.Xr newfs 8 ,
.Xr vnconfig 8
.Sh HISTORY
The vnode disk driver was originally written at the University of
Utah.
The compression handling is based on code by
.An Cliff Wright
.Aq cliff@snipe444.org .
.Sh BUGS
The
.Nm
driver does not work if the file does not reside in a local filesystem.