README

		    H. Peter Anvin <hpa@zytor.com>
			   October 18, 2002


User tools for zisofs:

The user tools for zisofs come in two parts: a utility "mkzftree" and
a modification to mkisofs, which is part of the cdrtools package.  The
mkisofs change has been integrated in the cdrtools distribution as of
cdrtools-1.11a20; a patch for cdrtools-1.11a09 which is also tested
and working on cdrtools-1.10 is included with this package if you
insist on running an older version.


First create a directory tree containing compressed files:

	mkzftree input_dir compressed_dir

mkzftree will not overwrite an existing directory; you may want to "rm
-rf" the directory tree if you are doing this from a script:

Second, invoke the patched mkisofs with the -z option:

	mkisofs -z -R [other options] -o compressed.iso compressed_dir

IMPORTANT: you *must* enable RockRidge (-R or -r) since this is an
extensions to the RockRidge specification.  Without RockRidge, -z will
have no effect.

Note that if there are files you do not want compressed (for example,
files involved in booting, or README files you want to be readable
under all circumstances) you can simply put them in a separate tree
and not run mkzftree on that tree.

mkzftree will not compress files that end up larger when compressed;
if you want it to compress the files anyway, you can give the -f
option to mkzftree.

mkzftree also accepts a -u option (uncompress), which can be used to
convert a compressed tree back to normal form.  This can be used to
read a zisofs CD-ROM on a machine without zisofs kernel support.

This version of mkzftree supports a -p option (parallelize.)
Specifying -p and a parallelism (e.g. -p4) allows files (up to the
number specified) to compress in parallel.  Depending on your setup
and your data set size, this might speed things up if you are not
completely I/O bound.  Use -p0 to completely disable parallel
execution; this is the default.