xenial (4) geom_uncompress.4freebsd.gz

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>.