Hi! Wrote this small howto for making compressed CD's in Linux. New users will certainly appreciate the fact Linux provides much more features than just security,stability and speed as compared to other popular OS'es.

Making Compressed CDROM in Linux

Nikhil Joshi

Introduction

I had often wondered whether there is a way to zip your files, burn them on a CD and then decompress them on-the-fly to save space. Well the good news is there is a method to do the same! Linux provides a Transparent decompression extension to achieve the same. It is useful when you have a lot of text/HTML/ doc files to burn on the CD and you want to save the precious space. It is especially useful to view the e-books which are mostly in HTML format.

Prepare the Kernel

CAVEAT: Please note that the CD that we are going to make will only be readable in Linux environment as Windows does not have the Transparent decompression extension. First we have to enable the Transparent decompression extension in the kernel. Compiling the kernel is a tricky business and requires patience and will to learn something new. This link will certainly help you:

http://www.digitalhermit.com/linux/Kernel-Build-HOWTO.html

I'll outline the steps below:

1. Download and unpack the latest 2.6 series stable kernel from http:// www.kernel.org/ 2. Type make menuconfig 3. Goto File Systems -> CDROM/DVD Filesystems and enable Transparent decompression extension 4. make; make modules; make modules_install 5. Copy the bzImage to /boot and update the bootloader configuration appropriately

The commands

Now that we have the kernel ready let's see the commands. Put everything you want to compress in a directory. First we make a compressed directory hierarchy of the directory we want to compress.

$ mkzftree intree outree

creates a compressed directory (outree) out of a normal directory (intree). Now we will make an iso image out of the directory hierarchy.

$ mkisofs -o mycd.iso -R -allow-lowercase -allow-multidot -l -L - z outree

That's it!! We have created an iso file which we can burn using any CD Burning Software. I use k3b (http://www.k3b.org/) on Linux.

Conclusion

I created a normal iso image out of a directory tree and another iso image out of the compressed directory tree. The space savings were obvious: 591MB for normal iso and 448MB using compression. A gain of 143 MB. This directory tree had lots of PDF files which do not compress well as compared to ASCII text files. Overall the space saving was considerable and I am already a fan of Transparent decompression.