How can we make F17 be able to boot on Macs (with or without reFit)

Chris Murphy lists at
Sat Dec 24 23:55:57 UTC 2011

Volume 2

CSM-BIOS boot notes:

Apple hardware tested: 
mbp41 = MacBookPro 4,1 (2008), Nvidia Geforce8600M GT.
mbp82 = MacBookPro 8,2 (2011), Intel HD Graphics 3000 and AMD Radeon HD 6750M.

All notes based on booting with the Apple-EFI option-key startup menu to choose how to boot, not rEFIt.

1. After default install using any installation type, and reboot, neither model loads GRUB2 (and thus does not boot) by default. Pre or post-install work is needed.

2. Both models CAN boot and startup Fedora to a GUI login with pre- or post-install work.

	a.  'nogpt' kernel parameter for Fedora only installs produces a bootable system without post-install work.

	b.  In dual-boot (Mac OS + Fedora) anaconda isn't creating a hybrid MBR post-install, therefore Apple's EFI startup disk menu doesn't see the F16 installation. Further, creating the hybrid MBR in advance is useless as parted wipes out the hybrid MBR in favor of a protective MBR just prior to installation. (See 3 below for additional fallout of this behavior.)

	c. Triple boot (Mac OS, Fedora, Windows) is possible, but there are more ways this won't work, than will work. And more ways that will work, but aren't good partition schemes (invitations for data loss) since there really isn't such a thing as a safe hybrid MBR + GPT. I have found one or two that I think are about as "safe" as they can get, and it means that the user needs to install Mac OS, Windows, Fedora, in that order, but located on the disk in order: Mac OS, Fedora, Windows.

3. Anaconda +  parted consistently remove pre-existing hybrid MBRs, replacing them with protective MBRs. The hybrid MBR will exist in a case where Windows has already been installed (using Apple's Bootcamp application). If removed in favor of a protective MBR, Windows is no longer bootable. So not only is Fedora not bootable, a previously bootable Windows is no longer bootable. This happens with either EFI or BIOS mode installs of Fedora.

So either anaconda needs to proceed no further upon discovery of a hybrid MBR, or it needs to become pretty good at sorting out hybrid MBR and GPT schemes that are "safe".

4. gptsycnc:  I don't think gptsync has such a sophisticated heuristic for creating such hybrid MBRs - I regularly see it produce very linear MBRs while suggesting huge percentages of the disk are empty. Any MBR only aware tool would see these areas as fair game - what I call an invitation for data loss and probably not a good idea.

5. If all requirements are met, Apple's startup disk menu (option-key at startup chime) will present a single "Windows" disk icon which if selected will load GRUB2 and its menu. That "Windows" label is apparently hard coded in Apple's EFI for any foreign OS requiring legacy CSM-BIOS booting.

Additional EFI boot notes:

1. By default EFI//EFI/redhat/grub.efi isn't found by Apple's EFI and install a choosable option. If it and the .conf are moved to EFI//EFI/BOOT/BOOTX64.efi and .conf, both models have an "EFI Boot" labeled disk icon in the option-key startup menu. I'm guessing like the "Windows" equivalent, that "EFI Boot" is hardwired.

This is being addressed by this:

2. GRUB-EFI (legacy) regularly just hangs are loading the kernel and initramfs, on mbp41. I don't have this problem with GRUB2-EFI but I still have other problems mentioned in the previous email.

Chris Murphy
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