104 lines
2.6 KiB
Groff
104 lines
2.6 KiB
Groff
.\" ----------------------------------------------------------------------------
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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 September 10, 2004
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.Dt MKUZIP 8
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.Os
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.Sh NAME
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.Nm mkuzip
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.Nd compress disk image for use with
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.Xr geom_uzip 4
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class
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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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This allows for significant reduction of size of disk image at
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the expense of some CPU time required to decompress the data each
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time it is read.
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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 compressed 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 indent
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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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.Pa .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.
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Default value is 16384 bytes.
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The
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.Ar cluster_size
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should be a multiple of 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.
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For large cluster sizes (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.
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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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only several bytes from that cluster have to be read.
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.Pp
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The
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.Nm
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inserts tiny shell script at the beginning of the generated image,
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which makes it possible to
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.Dq run
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the image just like any other shell script.
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This script tries
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to load
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.Xr geom_uzip 4
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class if it is not loaded, configure image as an
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.Xr md 4
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disk device using
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.Xr mdconfig 8
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utility, and automatically mount it using
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.Xr mount_cd9660 8
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utility to the mount point provided as a first argument.
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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 4 ,
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.Xr geom_uzip 4 ,
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.Xr md 4 ,
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.Xr mdconfig 8 ,
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.Xr mount_cd9660 8
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.Sh DIAGNOSTICS
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.Ex -std
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.Sh AUTHORS
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.An Maxim Sobolev Aq sobomax@FreeBSD.org
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