VND(4) BSD Programmer's Manual VND(4)
vnd - Vnode Disk Driver
pseudo-device vnd [count]
The vnd 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. There are two variants, the traditional vnd that
bypasses the buffercache and thus is suitable for swap on files, but not
for building disk-images, and the svnd ("safe" vnd) variant that goes
through the buffercache, thereby maintaining cache-coherency after the
block-device is closed which makes it suitable for creating disk images.
The latter is not good for swapping on, though.
This document assumes that you're familiar with how to generate kernels,
how to properly configure disks and pseudo-devices in a kernel configura-
tion file.
In order to compile in support for the vnd, you must add a line similar
to the following to your kernel configuration file:
pseudo-device vnd 4 # vnode disk driver
The count argument is how many vnds memory is allocated for at boot time.
In this example, no more than 4 vnds may be configured.
There is a run-time utility that is used for configuring vnds. See
vnconfig(8) for more information.
/dev/{,r}{,s}vnd* - vnd device special files.
disklabel(5), MAKEDEV(8), config(8), disklabel(8), fdisk(8), fsck(8),
mount(8), newfs(8), vnconfig(8)
The vnd disk driver was originally written at the University of Utah. The
svnd variant was first seen in OpenBSD 2.1.
The vnd driver does not work if the file does not reside in a local
filesystem. However the svnd variant does.
MirBSD #10-current December 30, 1995 1