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Re: macbook EFI experiences

From: Isaac Dupree
Subject: Re: macbook EFI experiences
Date: Sat, 31 May 2008 14:57:21 -0400
User-agent: Thunderbird (X11/20080505)

Robert Millan wrote:
On Fri, May 30, 2008 at 05:01:51PM -0400, Isaac Dupree wrote:
You don't need to use the header of one of your partitions.  You can use
the MBR or even have a dedicated partition for core.img. Then you can install
the rest of GRUB in a filesystem that's not case unsensitive! ;-P
I know, but I don't entirely understand how it works and I'd rather not... and it gives me limited options: theoretical maximum of 5 I think, 1 in MBR and 1 in each of first four partitions (each with their own hacks).

You're confusing BIOS-based boot with msdos partition labels.  You can use
GPT just fine when booting from BIOS (although Intel tries to hide that
fact by embedding the GPT spec inside the EFI spec).

I have the hack which combines the two partition labels so I have both GPT and msdos labels. Which means that my first four partitions (only) are listed in msdos, and GPT is the really accurate one that MacOS and Linux use. However, I can't find a way to get into bootloader-land via BIOS without going through the msdos partitioning mechanism.

I much prefer being able to put as many .efi files as fit all on one partition, for refit to find. As it is, when I upgrade GRUB, there always has to be the fear that I did something wrong that I can't easily fix because it's not just in the location of my files (it's hidden in mbr/partition headers), and because I can't boot into Linux anymore because I broke the bootloader :-) It's been very lucky that I can so far always boot into OS X without going through GRUB, and edit my grub.cfg from there... That, and keeping 10.4 updated, are the two main reasons I ever boot into MacOS :-)

I think what we need here is to support MacOS boot from GRUB.  Then you
can use GRUB as your bootloader and don't need to use it as a piece of
glue between Refit and Linux..

Want to help us on that? :-)

that'd be nice... although I kind of like it how it is for me now, choosing Mac vs. GRUB in rEFIt, so I'm not *particularly* inspired to help :-)

Btw what's a CSM?
"Compatibility Support Modules", it's a name for the BIOS substitute that Apple added to EFI to support their "Boot Camp"/Windows.

Notice that, like "EFI", "BIOS" doesn't imply any underliing implementation;
it just defines an interface (Intel uses this confusion to pretend their
firmware is free, when in fact only its shell -EFI- is).  Unless I missed
something, Apple's BIOS is as much a BIOS as is any other one.

I think you're right about that. (Except that I don't think that even the EFI part of the firmware is free on Apple computers, as far as I know they've done proprietary modifications to the free example-implementation and not been interested in releasing firmware sources.)


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