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.\" Copyright (c) 2014, Luiz Otavio O Souza <loos@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd January 9, 2014
.Dt GEOM_UNCOMPRESS 4
.Os
.Sh NAME
.Nm geom_uncompress
.Nd "GEOM based compressed disk images"
.Sh SYNOPSIS
To compile this driver into the kernel, place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "options GEOM_UNCOMPRESS"
.Ed
.Pp
Alternatively, to load the driver as a module at boot time, place the
following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
geom_uncompress_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
framework provides support for compressed read only disk images.
This allows significant storage savings at the expense of a little CPU
time on each read.
Data written in the GEOM label area allows
.Nm
to detect compressed images which have been created with
.Xr mkulzma 8
or
.Xr mkuzip 8
and presented to the kernel as a logical disk device via
.Xr md 4 .
.Nm
creates a unique
.Pa md#.uncompress
device for each image.
.Pp
The
.Nm
device is subsequently used by the
.Fx
kernel to access the disk images.
The
.Nm
driver does not allow write operations to the underlying disk image.
To check which
.Xr md 4
devices match a given
.Nm
device:
.Bd -literal -offset indent
# geom uncompress list
Geom name: md0.uncompress
Providers:
1. Name: md0.uncompress
Mediasize: 52428800 (50M)
Sectorsize: 512
Mode: r1w0e0
Consumers:
1. Name: md0
Mediasize: 20864000 (20M)
Sectorsize: 512
Mode: r1w0e0
.Ed
.Sh SEE ALSO
.Xr GEOM 4 ,
.Xr md 4 ,
.Xr geom 8 ,
.Xr mkulzma 8 ,
.Xr mkuzip 8
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An "Maxim Sobolev" Aq sobomax@FreeBSD.org
and
.An "Aleksandr Rybalko" Aq ray@FreeBSD.org .
This manual page was written by
.An "Luiz Otavio O Souza" Aq loos@FreeBSD.org .
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