[syslinux] Stumped by extlinux After OS Upgrade

Ferenc Wagner wferi at niif.hu
Wed Nov 3 16:58:25 PDT 2010


John.Florian at dart.biz writes:

>> From: Ferenc Wagner <wferi at niif.hu>
>
>>> extlinux doesn't understand file systems like, say grub, does it?
>> 
>> Extlinux and Grub both have various "stages".  The difference is that
>> the second stage of Extlinux, which understands the filesystem, itself
>> resides in the boot filesystem, while it resides in the slack area for
>> Grub.  This is why you can break Extlinux with filesystem operations, by
>> messing with its second stage.  However, starting with the config file
>> everything is read by the filesystem code, so they are safe to play with
>> (doing so does not require bootloader interaction, like LILO does).
>
> Thanks for that excellent detail.  Just to make sure I fully understand 
> this, you're saying that the 2nd stage is responsible for finding, reading 
> and interpreting the config file, right?

Yes, and naturally for everything else the config file loads (until
possibly chaining into another bootloader).

> Further, the first stage expects to find the second stage in the boot
> file system, but the first stage doesn't understand ext file systems.
> Only the 2nd stage understands ext file systems.
>
> How does the first stage actually find the 2nd stage?

The installer patches in actual sector numbers.  In other words, by
absolute position on the partition.
-- 
Regards,
Feri.




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