1 .\" ----------------------------------------------------------------------------
2 .\" "THE BEER-WARE LICENSE" (Revision 42):
3 .\" <sobomax@FreeBSD.ORG> wrote this file. As long as you retain this notice you
4 .\" can do whatever you want with this stuff. If we meet some day, and you think
5 .\" this stuff is worth it, you can buy me a beer in return. Maxim Sobolev
6 .\" ----------------------------------------------------------------------------
10 .Dd September 10, 2004
15 .Nd compress disk image for use with
22 .Op Fl s Ar cluster_size
27 utility compresses a disk image file in such a way that the
29 class will be able to decompress resulting image in run-time.
30 This allows for significant reduction of size of disk image at
31 the expense of some CPU time required to decompress the data each
33 Internally, operation is done in two phases as follows:
38 image is split into clusters and each cluster compressed using
41 Resulting set of compressed clusters along with headers allowing to
42 independently locate each individual cluster is written into
47 .Bl -tag -width indent
51 The default is to use the input name with the suffix
53 .It Fl s Ar cluster_size
56 as the size of chunks the file being split up into.
57 Default value is 16384 bytes.
60 should be a multiple of 512 bytes.
62 Display verbose messages.
65 Compression ratio largely depends on the cluster size used.
66 For large cluster sizes (16K and higher), typical compression ratios
67 are only 1-2% less than those achieved with the
70 However, it should be kept in mind that larger cluster
71 sizes lead to higher overhead in the
73 class, as the class has to decompress the whole cluster even if
74 only several bytes from that cluster have to be read.
78 inserts tiny shell script at the beginning of the generated image,
79 which makes it possible to
81 the image just like any other shell script.
85 class if it is not loaded, configure image as an
89 utility, and automatically mount it using
91 utility to the mount point provided as a first argument.
103 .An Maxim Sobolev Aq sobomax@FreeBSD.org