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Clarify/extend in several places and make sure that everything matches reality.

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sobomax 2004-09-10 22:26:31 +00:00
parent 2736322b28
commit b9945320c2
1 changed files with 32 additions and 16 deletions
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48
usr.bin/mkuzip/mkuzip.8
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@ -12,9 +12,9 @@
.Os
.Sh NAME
.Nm mkuzip
.Nd compress a
.Nd compress disk image for use with
.Xr geom_uzip 4
image
class
.Sh SYNOPSIS
.Nm
.Op Fl v
@ -26,11 +26,11 @@ 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:
class will be able to decompress resulting image in run-time.
This allows for significant reduction of size of disk image 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
@ -38,7 +38,7 @@ An
image is split into clusters and each cluster compressed using
.Xr zlib 3 .
.It
Resulting set of clusters along with headers allowing to
Resulting set of compressed clusters along with headers allowing to
independently locate each individual cluster is written into
output file.
.El
@ -54,30 +54,46 @@ The default is to use the input name with the suffix
Use
.Ar cluster_size
as the size of chunks the file being split up into. Default value
is 16K. The
is 16384 bytes. The
.Ar cluster_size
should be multiple of block size of the
.Xr geom_uzip 4
device (usually 512 bytes).
should be multiple of 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
large cluster sizes (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.
only several bytes from that cluster have to be read.
.Pp
The
.Nm
inserts tiny shell script at the beginning of the generated image,
which makes it possible to
.Qq run
the image just like any other shell script. This script tries
to load
.Xr geom_uzip 4
class if it is not loaded, configure image as a
.Xr md 4
disk device using
.Xr mdconfig 8
utility and automatically mount it using
.Xr mount_cd9660 8
utility to the mount point provided as a first argument.
.Sh SEE ALSO
.Xr gzip 1 ,
.Xr zlib 3 ,
.Xr geom_uzip 4 ,
.Xr boot 8 ,
.Xr loader 8
.Xr geom 4 ,
.Xr md 4 ,
.Xr mdconfig 8 ,
.Xr mount_cd9660 8 .
.Sh DIAGNOSTICS
Exit status is 0 on success and >0 on error.
.Sh AUTHORS