While booting from the CD the kernel is started, if the kernel starts up it loads an initial file system from a file, this is the initrd (here called rescue). This file is compressed and will be extracted to the memory and mounted as root file system. All needed files like basic commands (ls,cp) and the install script are contained in this root file system.
In the /mdk/bootCD/root are all files needed for the initrd. If you want to make changes to the start up process of the boot CD you should edit the /mdk/bootCD/root directory. The mkRescue.sh script makes an empty initrd file, formats it with ext2 file system, copies needed files to initrd and compresses it to rescue.gz. For further information have a look at the mkRescue.sh script.
root
2015-09-06