Custom OpenBSD 4.2 bootable CD
With the release of OpenBSD 4.2, you will find that cdrom42.fs was not provided in OpenBSD official ftp sites. However, it is relatively easy to custom build your own OpenBSD 4.2 bootable installer CD. I will show you the steps in making your own puffer fish El Torito. 
CREATE CD STRUCTURE
Create the OpenBSD bootable CD structure with this command,
%mkdir -p ~/OpenBSD/4.2/i386
DOWNLOAD OPENBSD FILES
Use ncftp or wget to download the necessary files off OpenBSD ftp site.
%cd ~/OpenBSD/4.2/i386 && ncftp ftp://ftp.jp.openbsd.org/pub/OpenBSD/4.2/i386 ncftp /OpenBSD/4.2/i386 > get *
Note : install42.iso is a bootable OpenBSD installer by itself. You should exclude that file.
CREATE CDROM42.FS
As this file is absent, creation of cdrom42.fs is required in order to make bootable OpenBSD iso. Bootable “El Torito” CDROMs usually use a boot loader. The loader will boot disk image located inside the iso9660 filesystem. This cdrom42.fs is the file that contains both boot loader and disk image. Not too worry. It is trivial.
Thanks to Rainer Krienke for creating a nice El Torito boot image extractor in PERL, called “geteltorito“. Grab a copy/make executable and extract El Torito boot image from the file cdemu42.iso with this simple command.
%geteltorito cdemu42.iso > cdrom42.fs Booting catalog starts at sector: 29 Manufacturer of CD: Copyright (c) 2007 Theo Image architecture: x86 Boot media type is: 2.88meg floppy El Torito image starts at sector 30 and has 5760 sector(s) of 512 Bytes Image has been written to stdout ....
CUSTOMIZATION
You can add whatever files you want them to be included. Just copy them to ~/OpenBSD/ . I normally will put stuff like ports.tar.gz, src.tar.gz, sys.tar.gz and etc.
CREATE OPENBSD BOOTABLE INSTALLER CD
mkisofs comes handy in creating our bootable CD. Just issue this command and wait for it to be generated.
%cd ~/OpenBSD && mkisofs -vrTJV "OpenBSD 4.2" -b 4.2/i386/cdrom42.fs -c boot.catalog -o OpenBSD42.iso ~/OpenBSD/
Now you will have OpenBSD42.iso. Burn it to a blank CD-R and Volia! Do support the OpenBSD project. Buy CD/T-shirt. They look really cool!!
Tuesday, November 6th, 2007
