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+
+What is El Torito?
+------------------
+Simply put, El Torito is a specification that says how a cdrom should
+be formatted such that you can directly boot from it.
+
+The "El Torito" spec says that ANY cdrom drive should work (scsi/eide)
+as long as the BIOS supports El Torito. So far this has only been
+tested with EIDE drives because none of the scsi controllers that has
+been tested so far appears to support El Torito. The motherboard
+definately has to support El Torito. The ones that do let you choose
+booting from HD, Floppy, Network or CDROM.
+
+How To Make Bootable CDs
+------------------------
+
+For the x86 platform, many BIOS's have begun to support bootable CDs.
+The standard my patches for genisoimage is based on is called "El Torito".
+
+The "El Torito" standard works by making the CD drive appear, through BIOS
+calls, to be a normal floppy drive. This way you simply put an floppy
+size image (exactly 1440k for a 1.44 meg floppy) somewhere in the
+iso fs. In the headers of the iso fs you place a pointer to this image.
+The BIOS will then grab this image from the CD and for all purposes it
+acts as if it were booting from the floppy drive. This allows a working
+LILO boot disk, for example, to simply be used as is.
+
+It is simple then to make a bootable CD. First create a file, say "boot.img"
+which is an exact image of the boot floppu currently in use. There is
+at least one HOWTO on making bootable floppies. If you have a bootable
+floppy handy, you can make a boot image with the command
+
+dd if=/dev/fd0 of=boot.img bs=10k count=144
+
+assuming the floppy is in the A: drive.
+
+Place this image somewhere in the hierarchy which will be the source
+for the iso9660 filesystem. It is a good idea to put all boot related
+files in their own directory ("boot/" under the root of the iso9660 fs,
+for example), but this is not necessary.
+
+One caveat - Your boot floppy MUST load any initial ramdisk via LILO,
+not the kernel ramdisk driver! This is because once the linux kernel
+starts up, the BIOS emulation of the CD as a floppy disk is circumvented
+and will fail miserably. LILO will load the initial ramdisk using BIOS
+disk calls, so the emulation works as designed.
+
+The "El Torito" specification requires a "boot catalog" to be created as 
+ll.
+This is a 2048 byte file which is of no interest except it is required.
+My patches to genisoimage will cause it to automatically create the
+boot catalog. You must specify where the boot catalog will go in the
+iso9660 filesystem. Usually it is a good idea to put it the same place
+as the boot image, and a name like "boot.catalog" seems appropriate.
+
+
+So we have our boot image in the file "boot.image", and we are going to
+put it in the directory "boot/" under the root of the iso9660 filesystem.
+We will have the boot catalog go in the same directory with the name
+"boot.catalog". The command to create the iso9660 fs in the file
+bootcd.iso is then
+
+genisoimage -b boot/boot.img -c boot/boot.catalog -o bootcd.iso .
+
+The -b option specifies the boot image to be used (note the path is
+relative to the root of the iso9660 disc), and the -c option is
+for the boot catalog file.
+
+Now burn the CD and its ready to boot!
+
+CAVEATS
+-------
+
+I don't think this will work with multisession CDs.
+
+If your bootable floppy image needs to access the boot floppy, it has
+to do so through BIOS calls. This is because if your O/S tries to talk to
+the floppy directly it will bypass the "floppy emulation" the El Torito spec
+creates through BIOS. For example, under Linux it is possible to
+have an initial RAM disk loaded when the kernel starts up. If you let the
+kernel try to read in the initial RAM disk from floppy, it will fail
+miserably because Linux is not using BIOS calls to access the floppy drive.
+Instead of seeing the floppy image on the CD, Linux will be looking at
+the actually floppy drive.
+
+The solution is to have the initial boot loader, called LILO, load your
+initial RAM disk for you.  LILO uses BIOS calls entirely for these
+operations, so it can grab it from the emulated floppy image.
+
+I don't think making a CD bootable renders it unreadable by non-El Torito
+machines. The El Torito spec uses parts of the iso9660 filesystem which
+were reserved for future use, so no existing code should care what it does.
+
+Genisoimage currently stores identification records in the iso9660 filesystem
+saying that the system is a x86 system. The El Torito spec also allows
+one to write PowerPC or Mac id's instead. If you look at the code in write.c
+you could figure out how to change what is written.
+
+/* @(#)README.eltorito	1.2 00/03/18 eric */
+/* Edited for name change by Eduard Bloch, mkisofs -> genisoimage */
+