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GEOM_UNCOMPRESS(4) Device Drivers Manual GEOM_UNCOMPRESS(4)

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.conf(5): 
geom_uncompress_load="YES"

DESCRIPTION

The geom_uncompress 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 geom_uncompress 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). geom_uncompress creates a unique md#.uncompress device for each image.
The geom_uncompress device is subsequently used by the FreeBSD kernel to access the disk images. The geom_uncompress driver does not allow write operations to the underlying disk image. To check which md(4) devices match a given geom_uncompress 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

The geom_uncompress driver was written by Maxim Sobolev ⟨sobomax@FreeBSD.org⟩ and Aleksandr Rybalko ⟨ray@FreeBSD.org⟩. This manual page was written by Luiz Otavio O Souza ⟨loos@FreeBSD.org⟩.
January 9, 2014 Debian