freebsd man page for geom_uncompress

GEOM_UNCOMPRESS(4)					   BSD Kernel Interfaces 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>.

BSD
								  January 9, 2014							       BSD