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