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SDB Talk:Installation on a Mac
The first rEFInd paragraph is very wrong, but I don't want to simply delete it without writing more in its place. I just don't know what to replace it with. Forum thread Installation-on-a-Mac details my iMac experience last summer and last month. I used rEFInd with Snow Leopard, but never got rEFInd to work again after upgrading to El Capitan. UEFI Grub is loading MacOS.
Highlights of my configuration include renaming /etc/grub.d/40_custom to 06_custom, but not changing its content; and booting from /boot/grub2/custom.cfg that I created entirely from scratch, little different than how I multiboot on generic UEFI PCs. This produces an identical Grub menu head regardless whether 15.0 or 15.1 has last wrested ostensible boot control from the other.
My directories in /boot/efi/EFI/ are named APPLE, opensuse150 and opensuse151, the latter two via customization of /etc/default/grubs' GRUB_DISTRIBUTOR= lines. They are the names shown by efibootmgr. My /etc/default/grub files also contain GRUB_DISABLE_OS_PROBER=true, since the most used Grub menu entries at runtime are those at the top, leaving whatever follows to be ignored unless a prior kernel or rescue boot are wanted or needed.
This was most important to me: Booting From Install CD / DVD
To make your Mac boot from a Linux or Windows CD or DVD, you need to hold down the 'Alt' key as the Mac starts up (EFI-Boot), keep holding it down until it is obvious the CD is booting (pre 2012).
On a MacBook Air (booting from a pen drive) the alt/option key needs to be pressed. Boot to the installation via the EFI method (you should see a selection after pressing the alt/option key).
=> There is an alternative way to boot from DVD which does not work.