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Re: CDROM booting issues for Linux on Sparc

On Thu, May 23, 2002 at 05:15:15PM -0500, Phil Howard wrote:
> What is the issue that makes booting Linux from a CDROM on Sparc
> so complicated?  I'm told by Jörg Schilling that mkisofs from
> cdrtools can make a CD that boots Solaris just fine.  He points
> out that SILO "misbehaves", but as yet I don't know what that
> mishaviour actually is.
> What will it take to make a CDROM that can boot Linux on Sparc
> without modifying mkisofs?  Or can someone show that this is
> not the case?
> I want to get this long problem resolved once and for all, but
> with so many people holding back on information, it has been so
> far hard to do.  Does anyone here have information that they are
> willing to share on the matter?

There is no holding back on information. You just need to read the SILO
docs that explains it all. Basically, SILO uses cd.b as the "boot
sector" in mkisofs, munging the solaris way of having a different slice
for each arch (sun4c/sun4d/sun4e/sun4u/sun4d/etc) to all point to this
one boot block.

After that, it loads up the second.b, which in turn reads silo.conf, and
continues the bootup.

Now, for cd.b to read in and execute second.b from the cdrom, it needs
to know which physical sector second.b starts on.

Now, the way SILO has always done this is with some special options in
mkhybrid/mkisofs so that cd.b gets "patched" up with the sector for
second.b. That's all there is to it. We could use the "..." method, if
only there was a way to patch up cd.b afterwards.

This is exactly how things work on a regular disk for SILO (the sector

This could all be made into a seperate tool from mkisofs, which would
work like:

### Setup the iso image
# mkdir sparc-iso/boot sparc-iso/etc
# cp /boot/vmlinux /boot/second.b sparc-iso/boot
# cp silo-initrd.conf sparc-iso/etc/silo.conf
# cp initrd-image sparc-iso/boot

### Create the ISO using normal sparc boot options
# mkisofs -G /boot/cd.b -B ... -o sparc-bootable.iso sparc-iso/

### Make the image bootable
# silo-mkcdboot --second /boot/second.b --config /etc/silo.conf sparc-bootable.iso

The second tool has yet to be developed. I have in fact already begun
checking out how to do this and including it with SILO. It would
alleviate all the needed things in mkisofs. You are more than welcome to
complete it if you want.

Debian     - http://www.debian.org/
Linux 1394 - http://linux1394.sourceforge.net/
Subversion - http://subversion.tigris.org/
Deqo       - http://www.deqo.com/

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