geom_uncompress (4)

Leading comments

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
  ...

(The comments found at the beginning of the groff file "man4/geom_uncompress.4freebsd".)

NAME

geom_uncompress - GEOM based compressed disk images

SYNOPSIS

To compile this driver into the kernel, place the following line in your kernel configuration file:

options GEOM_UNCOMPRESS

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf5:

geom_uncompress_load="YES"

DESCRIPTION

The ifconfig 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 ifconfig to detect compressed images which have been created with mkulzma(8) or mkuzip(8) and presented to the kernel as a logical disk device via md(4). ifconfig creates a unique md#.uncompress device for each image.

The ifconfig device is subsequently used by the Fx kernel to access the disk images. The ifconfig driver does not allow write operations to the underlying disk image. To check which md(4) devices match a given ifconfig device:

# 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

SEE ALSO

GEOM(4), md(4), geom(8), mkulzma(8), mkuzip(8)

AUTHORS

An -nosplit The ifconfig 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 .