freebsd-skq/share/man/man4/geom_uzip.4

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.Dd October 9, 2006
.Dt GEOM_UZIP 4
.Os
.Sh NAME
.Nm geom_uzip
.Nd "GEOM based compressed disk images"
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "options GEOM_UZIP"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
geom_uzip_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
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
.Nm
to detect compressed images which have been created with
.Xr mkuzip 8
and presented to the kernel as a logical disk device via
.Xr md 4 .
.Nm
creates a unique
.Pa md#.uzip
device for each image.
.Pp
The
.Nm
device is subsequently used by the
.Fx
kernel to access the disk images.
The
.Nm
driver does not allow write operations to the underlying disk image.
To check which
.Xr md 4
devices match a given
.Nm
device:
.Bd -literal -offset indent
# geom uzip list
Geom name: md1.uzip
Providers:
1. Name: md1.uzip
   Mediasize: 22003712 (21M)
   Sectorsize: 512
   Mode: r1w0e1
Consumers:
1. Name: md1
   Mediasize: 9563648 (9.1M)
   Sectorsize: 512
   Mode: r1w0e1
.Ed
.Sh SEE ALSO
.Xr GEOM 4 ,
.Xr md 4 ,
.Xr geom 8 ,
.Xr mkuzip 8
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Max Khon Aq Mt fjoe@FreeBSD.org .
This manual page was written by
.An Ceri Davies Aq Mt ceri@FreeBSD.org .