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.\" ----------------------------------------------------------------------------
.\" "THE BEER-WARE LICENSE" (Revision 42):
.\" <sobomax@FreeBSD.ORG> wrote this file. As long as you retain this notice you
.\" can do whatever you want with this stuff. If we meet some day, and you think
.\" this stuff is worth it, you can buy me a beer in return. Maxim Sobolev
.\" ----------------------------------------------------------------------------
.\"
.\" $FreeBSD$
.\"
.Dd July 29, 2001
.Dt MDGZIP 8
.Os
.Sh NAME
.Nm mkuzip
.Nd compress a
.Xr geom_uzip 4
image
.Sh SYNOPSIS
.Nm
.Op Fl v
.Op Fl o Ar outfile
.Op Fl s Ar cluster_size
.Ar infile
.Sh DESCRIPTION
The
.Nm
utility compresses a disk image file in such a way that the
.Xr geom_uzip 4
class will be able to decompress resulting image in run-time
when it loaded into memory. This allows for significant reduction
of memory footprint of memory-based filesystem at the expense of
some CPU time required to decompress the data each time it is
read. Internally, operation is done in two phases as follows:
.Bl -enum
.It
An
.Ar infile
image is split into clusters and each cluster compressed using
.Xr zlib 3 .
.It
Resulting set of clusters along with headers allowing to
independently locate each individual cluster is written into
output file.
.El
.Pp
The options are:
.Bl -tag -width Fl
.It Fl o Ar outfile
Name the output file
.Ar outfile .
The default is to use the input name with the suffix
.Sq .uzip .
.It Fl s Ar cluster_size
Use
.Ar cluster_size
as the size of chunks the file being split up into. Default value
is 16K. The
.Ar cluster_size
should be multiple of block size of the
.Xr geom_uzip 4
device (usually 512 bytes).
.It Fl v
Display verbose messages.
.El
.Sh NOTES
Compression ratio largely depends on the cluster size used. For
large cluster sizes of (16K and higher) typical compression ratios
are only 1-2% less than those achieved with the
.Xr gzip 1
utlity. However, it should be kept in mind that larger cluster
sizes lead to higher overhead in the
.Xr geom_uzip 4
class, as the class has to decompress the whole cluster even if
literally only several bytes from that cluster have to be read.
.Sh SEE ALSO
.Xr gzip 1 ,
.Xr zlib 3 ,
.Xr geom_uzip 4 ,
.Xr boot 8 ,
.Xr loader 8
.Sh DIAGNOSTICS
Exit status is 0 on success and >0 on error.
.Sh AUTHORS
.An Maxim Sobolev Aq sobomax@FreeBSD.org .
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