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Re: How to prepare an ISO 9660 CD for booting via GRUB ?

From: Thomas Schmitt
Subject: Re: How to prepare an ISO 9660 CD for booting via GRUB ?
Date: Sat, 17 Apr 2010 19:52:20 +0200


Vladimir Serbinenko:
> efi booting [...] it's basically standard no-emul
> eltorito except:
> platform_id[0] = 0xef;

I assume you mean the Platform ID as of El Torito
specs about the Boot Catalog and its Validation
Entry. (Chapter 2, figure 2)

That should be easy to test.
In libisofs/eltorito.c, there is a line
    ve->platform_id[0] = 0; /* 0: 80x86, 1: PowerPC, 2: Mac */

A bit more work will be to make this controllable
by the libisofs API.

> No isolinux patching (could this one be disabled by default?)

You mean mkisofs -boot-info-table ?
(Code in libisofs/eltorito.c :
  int patch_boot_image(uint8_t *buf, Ecma119Image *t, size_t imgsize)

Just yesterday i moved that setting from option
-b to option -boot-info-table, which was a noop.
So if you omit -boot-info-table then patching
should be disabled.

Before i release xorriso-0.5.4 i will make a
(dummy) test.

> load_sectors should be set to the size of whole
> image instead of just 4 sectors 

You mean mkisofs -boot-load-size ?
This is implemented in -as mkisofs emulation.
For a test you may set it manually.
Unit is 512 bytes. Default is 4.

> Can we have a --efi-boot <image> option which will do this?

This shall then determine the -boot-load-size
from the size of the <image> file ?
Should be possible.

But it seems more natural to state

  -b <image> --efi-boot

in comparison to traditional

  -b <image> -boot-info-table

Whatever, except the small hardcoded change in
the currently uploaded xorriso-0.5.3 with time
stamp 2010.04.17.171232 should already be able
to produce such an ISO image.
If a missing option -boot-info-table causes
problems, then i will solve them soon.

Please make a test. I can only check by od,
but have no idea how to prepare something that
would really boot.


> On another note: can it be ensured that boot images and files boot/grub
> directory? I've come across a bug which seems to be triggered by images
> being after 2GiB mark on DVD.

There seem words missing around "directory".

Do i get it right that you want the LBA of the
boot catalog and the boot image to be as low
as possible ?

I will have to explore how i can achieve that.


Today i released libisofs-0.6.30. It will be the
fundament of libisoburn-0.5.4, which i plan to
release in the next few days, together with GNU
Then we can urge distribution maintainers to
update their packages.

The API change for adjustable Platform ID would
become part of libisofs-0.6.32 and xorriso-0.5.6.


Have a nice day :)


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