[syslinux] Sysinux 6 will not boot ISOs on BIOS (i.e. pre-UEFI) systems

[Mattias Schlenker]

Am 25.11.2013 08:18, schrieb Thomas Schmitt:
>
>>   < 2013.11.23 = BAD
>>   > 2013.11.24 = OK
>>   <       Load LBA: 136026 (0x0002135a)
>>   ---
>>   >       Load LBA: 22792 (0x00005908)
>>   Maybe too high?
> A high boot image address once was the reason for a boot
> failure of Debian ia64. (Itanium, not x86_64. EFI, not BIOS.)
>
> You may influence the address of the boot image by
>     --sort-weight 2 /isolinux/isolinux.bin
> or
>     --sort-weight -1 /isolinux/isolinux.bin
>
> The former pushes it to a low address, the latter to a high one.

I can confirm problems on some older BIOSes where boot images located 
beyond LBA 65535 are not loaded. Thomas and I still have to figure out 
whether the whole image has to be within this boundary or just the first 
LBA. For this reason I usually use the following weighting:

    5 /boot/isolinux/isolinux.bin
    4 /boot/isolinux
    3 /boot/kernel
    2 /boot/ (containing /boot/grub, /boot/efi.img and stuff - you might
    further differentiate here)
    1 /casper or /lesslinux - directories with SquashFS containers or
    whatever is used by your live CD or installer
    0 everything else (autorun.inf, stuff for Windows, additional debs etc.)

With this sort order, you make first sure that everything Isolinux 
related (com32 modules, configuration) is found within LBA 65535. Second 
the head of the drive has to be repositioned in smaller increments since 
the physical positions of the files in the ISO represents the load 
order. Working with directories (/boot/isolinux, /boot/kernel, 
/boot/grub) makes sure that many large kernels and ramdisks (often 
located in the isolinux directory) do not accidentially push Isolinux 
related files to higher addresses - of course you could weight every 
single file, but this is really a PITA).

Regards,
Mattias


-- 
Mattias Schlenker - Redaktion + EDV-Beratung + Linux-CD/DVD-Konzepte
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