GEOM_UNCOMPRESS(4FREEBSD) - man page online | special files

GEOM based compressed disk images.

January 9, 2014
GEOM_UNCOMPRESS(4)                 BSD Kernel Interfaces Manual                GEOM_UNCOMPRESS(4)


geom_uncompress — GEOM based compressed disk images


To compile this driver into the kernel, place the following line in your kernel configura‐ tion 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"


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


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


The geom_uncompress driver was written by Maxim Sobolev <> and Aleksandr Rybalko <>. This manual page was written by Luiz Otavio O Souza <>.
BSD January 9, 2014 BSD
This manual Reference Other manuals
geom_uncompress(4freebsd) referred by
refer to md(4)