freebsd-skq/share/man/man4/geom_uncompress.4
Baptiste Daroussin 6c89995002 use .Mt to mark up email addresses consistently (final part)
PR:		191174
Submitted by:	Franco Fichtner <franco at lastsummer.de>
2014-06-26 21:46:14 +00:00

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.\" Copyright (c) 2014, Luiz Otavio O Souza <loos@FreeBSD.org>
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.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 Mt sobomax@FreeBSD.org
and
.An Aleksandr Rybalko Aq Mt ray@FreeBSD.org .
This manual page was written by
.An Luiz Otavio O Souza Aq Mt loos@FreeBSD.org .