directories:

boot ....... contains files to boot Live CD

base ....... contains base (essential) modules for filesystem. All .mo files from this directory will be used.
modules .... contains additional modules for filesystem. All .mo files from this directory will be used.
optional ... contains optional modules, which are loaded only with "load=modulename.mo" boot option.
rootcopy ... contains files which are directly copied to root directory / while booting, overwriting originals.


files:

make_iso.sh .... script to build new iso in Linux
