geom_uncompress(4) GEOM based compressed disk images


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

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



The 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 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). creates a unique md#.uncompress device for each image.

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

# geom uncompress list
Geom name: md0.uncompress
1. Name: md0.uncompress
   Mediasize: 52428800 (50M)
   Sectorsize: 512
   Mode: r1w0e0
1. Name: md0
   Mediasize: 20864000 (20M)
   Sectorsize: 512
   Mode: r1w0e0


An -nosplit The driver was written by An Maxim Sobolev Aq [email protected] and An Aleksandr Rybalko Aq [email protected] . This manual page was written by An Luiz Otavio O Souza Aq [email protected] .