freebsd-skq/share/man/man4/vn.4

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.\" Copyright (c) 1995 Jason R. Thorpe.
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.Dd December 30, 1995
.Dt VN 4
.Os
.Sh NAME
.Nm vn
.Nd vnode disk driver
.Sh SYNOPSIS
.Cd "pseudo-device vn"
.Sh DESCRIPTION
The
.Nm
driver uses swap or a file as backing store to abstract-out a character and
block device which may then be used like a disk.  The
.Nm
driver supports both labeled and unlabeled pseudo-disks and is useful for
a variety of applications, including swap files and building mini-root,
floppy, or CDRom disk images.
.Nm
may also be used to create temporary swap-backed filesystems, such as /tmp,
in a somewhat less memory-hungry manner then MFS.
.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
.Nm vn ,
you must add a line similar
to the following to your kernel configuration file:
.Bd -unfilled -offset indent
pseudo-device	vn		#Vnode driver
.Ed
.Pp
.Nm
may also exist as a kernel module to be automatically loaded into the 
system when you run the vnconfig command for the first time.
.Pp
There is a run-time utility that is used for configuring
.Nm vn Ns 's .
See
.Xr vnconfig 8
for more information.
.Sh BUGS
The
.Nm
driver does not work if the file does not reside in a local filesystem.
.Sh FILES
/dev/{,r}vn* - vn device special files.
.Pp
.Sh HISTORY
The vnode disk driver was originally written at the University of
Utah and was substantially modified by FreeBSD developers to add 
swap-backed support.
.Sh SEE ALSO
.Xr config 8 ,
.Xr fsck 8 ,
.Xr MAKEDEV 8 ,
.Xr mount 8 ,
.Xr newfs 8 ,
.Xr vnconfig 8 .