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