Ubuntu 12.04 Boot Capability (related to BIOS)

[GatoLoko]

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El 20/11/12 03:35, tsukishiro yamazaki escribió:
> Hello all,
> 
> I just wanted to ask if it's possible at the level of Ubuntu 12.04
> to boot from a specific address in storage or memory. We are doing
> a small experiment wherein an option is added in BIOS that will
> load Ubuntu from a specified location. Is this possible? If there
> are supporting documents for this one, can someone point me where
> to find them? I tried reading the official guides but haven't found
> what I was looking for.

You can do anything you can code, and in this case your best chance to
find what you are looking for is in the code or documentation of any
boot manager like GRUB, LILO or whichever you prefer.

This article describes the current boot process from the BIOS to
executing the kernel, and has links to other related documents that
may be interesting:
http://www.ibm.com/developerworks/linux/library/l-linuxboot/

While possible, I think this is a very bad idea. During the lifetime
of any Ubuntu release, there will be updates to the kernel. With each
single kernel update, you would need to tell that BIOS where the new
kernel is. This by itself makes it a bad idea, because you would need
a tool to edit the BIOS config from the running system when there is
an update, or to enter the BIOS and manually reconfigure it.

Not only that, but the BIOS would need to understand many file
systems, since Ubuntu will store the kernel in different ways
depending on which file system it's using to store the files. More so,
the file system may suffer fragmentation, storing the kernel image
file in multiple pieces, or, may be compressed, encrypted .... so the
BIOS would need a deep understanding of many things.

Then, supposing you are able to load the kernel, you still need to
find/load the initrd, provide the kernel with boot time parameters, a
way to tell the BIOS those parameters and edit them when necessary, ...

Basically you would need to add all the complexities of a complete
boot manager inside your BIOS.

Simplifying it, you only need to load a kernel image into ram and
executing it. Understanding it, you need a lot of work just to boot
the system, and including that process inside the BIOS adds a lot of
problems to resolve.

- -- 
Raúl Soriano


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