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Remastering a Custom Knoppix Distribution, Part 2

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Continuing from Matt Lesko's last article, he now takes your Knoppix customization to a new level. Now that you know how to add user-land software to your disc, he'll show you how to add new kernels, customize the boot process, and add new drivers.
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In the last article, I covered the basics of organizing your own Knoppix distribution. I focused primarily on software installation and removal, but you should know that there are other options that present difficulties with Knoppix. Specifically, with Knoppix, upgrading the kernel isn't done in the normal fashion, and some of the configuration possibilities that are available with a bootable CD are not widely known. We will use some techniques from my first article, "Insert title here" and continue working from the Knoppix 3.8 distribution.

Changing the Bootscreen

When Knoppix boots normally, a splash screen with a logo is presented, along with a command line for typing in various Knoppix "cheat-codes" If you are already customizing your distribution, it makes sense to change these options to suit your needs as well. The bootable CD works through software called ISOLINUX and the configuration files are found on the CD in the boot/isolinux directory. You can find more information about ISOLINUX at http://syslinux.zytor.com/iso.php.

Once you're ready, move to the copy of this directory on your local system (if you are working from the last article, this would be /knoppix-cd/KNOPPIX/KNOPPIX.build/boot/isolinux). Open the file boot.img and you will see that is it a normal text file, albeit with some special ASCII characters. The first line contains the location of the image graphic, in a special format that I'll discuss promptly. After that is the text displayed by the bootloader—replace this with the text of your choosing. The text files f1, f2, and f3, located in the same directory, display the text shown when a user presses the F1, F2, or F3 button, respectively. You can use these files to provide additional information to a user at boot time.

Those files generally use advanced ASCII formatting that can become a hassle to change if you still want them to align correctly. If you have a win32 box available, you case use the isolinux-mate software from http://members.chello.at/bobby100/ILM.htm to assist in making the splash screen visually satisfying. For those without, a primer on the ASCII codes and how they work is available at http://members.chello.at/bobby100/ILpart2.htm.

In order to replace the boot logo, you must first create your own and then save it as a RAW ppm file, with less than 16 colors. The facilities for displaying graphics before the OS boots are not terrific, so try not to get too carried away. Convert the ppm file into a LSS16 file, (through the ppmtolss16 program, which is part of the syslinux package). Install it through apt-get, or download it from the ISOLINUX website listed previously. The ppmtolss16 program takes a ppm graphics file from standard input and outputs the special graphics file.

root@tty1[isolinux]# ppmtolss16 < logo.ppm > logo.16
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