[SOLVED] Trouble with EFI booting on 64-bit Mac using rEFInd

[propjow]

Hi All,
I'm looking to install AMD64 Gentoo alongside OS X on a 64-bit Mac, setting it up to boot directly from rEFInd (without grub) and I'm running into some trouble. Specifically, when I boot the Linux kernel from the rEFInd menu I'm given the error message:

[ulenrich]

Some ideas:
1. Perhaps it is a special case using the name bootx64.efi:
name it for example: (EFIPART)/EFI/Gentoo/kernel.efi
2. Also you can from refind chain load a normal grub (installed in a partition by using --force) .
3. rootfstype in cmdline:

[propjow]

Thanks for the suggestions ulenrich,
Re 1 and 3: I recompiled the kernel with "rootfstype=ext4" added to the built-in command line and copied it to a new EFI file on the EFI partition. rEFInd detects the new kernel but alas I get the same "Error: Unsupported" when I try to boot it.

I was hoping to avoid grub entirely to streamline the boot process, but I'm nearing the point where I might install it just to get Linux up and running. I should in theory be able to boot without grub however, no?

Thanks again.

[ulenrich]

I get a disadvantage booting in efi mode:
I cannot see any text mode console any more. This is because I use proprietary nvidia drivers. There should be a way to unload efi-framebuffer and loading an ordinary vga instead, but I don't know how to do it yet.

If you get it booted (with grub):
- turn on everything you want (external usb,dvb etc)
- make localyesconfig
This can get you a working kernel to boot without any initramfs. Be aware there are modules not available using this technique: microcode loader for example you have to activate manually by make menuconfig.

[srs5694]

What architecture type are you using? A 64-bit EFI can boot only a 64-bit (x86-64/AMD64/x64) Linux kernel, and a 32-bit EFI can boot only a 32-bit (x86/ia32) kernel. If you try to boot a 32-bit kernel from a 64-bit EFI or vice-versa, you'll get the "unsupported" message you report. Given that you've got CONFIG_EFI_STUB=y set in your kernel configuration, a mismatched architecture type is the most likely explanation. If this is the cause, then you have two choices:

• Re-install Gentoo using the correct architecture type.
  
• Use GRUB or some other boot loader that can handle the cross-architecture kernel loading.
  

One other thought occurs to me, and that is that the kernel file you've created is damaged or is the wrong file type. In a stock kernel compilation, you should be using the file /usr/src/linux/arch/x86/boot/bzImage. If you use some other file (say /usr/src/linux/arch/x86/boot/compressed/vmlinux), it probably won't work.

One more comment, although it's not the source of your problem: With the ESP mounted at /boot as you've done, copying your kernel to /boot/bzImage* or /boot/vmlinuz* should work with rEFInd; you shouldn't need to copy the kernel elsewhere or give it a filename extension of .efi. Using this name will also cause rEFInd to search for a refind_linux.conf file in which you can place kernel options, and to search for a matching initrd file. If you're installing manually, aren't using an initrd file, and have compiled your options into the kernel, you may not care about all this, but I thought I'd point it out because these features (particularly refind_linux.conf) can help you to experiment with your kernel options when you're setting things up.

[propjow]

Thanks, ulenrich and srs594.

Indeed you are likely correct that kernel was being compiled for the wrong architecture. I'd since come upon a post suggesting that Core 2 Duo Mac Minis before 2008 (such as my own, which is a 2007) have a 32 bit EFI.

I installed a 32-bit Gentoo and compiled, then installed a 32-bit kernel with the same EFI-related options as before. It's /usr/src/linux/arch/x86/boot/bzImage that is being copied over, by the way. On booting this new kernel I get:

[srs5694]

It looks like you're on the right track, propjow. Given the output you report, it seems that rEFInd is either not detecting the file as a Linux kernel (which it should be, given the name), or you don't have a refind_linux.conf file to pass it the kernel options. This file's format is pretty simple: It contains a series of lines, each with a name followed by kernel options. Both the name and the kernel options are enclosed in quotes, thus:

[propjow]

Thank you, srs5694.

So, I placed a refind_linux.conf file with what I believe are appropriate kernel options ('root=/dev/sda6 rootfstype=ext4') on the ESP and rEFInd did pick those options up on reboot, but still no luck -- it hangs after "Using load options 'root=/dev/sda6 rootfstype=ext4'". Hmm.

[srs5694]

Do you have an initrd file? If so, it should be auto-detected, but if it's not being auto-detected, you can add it as an option.

Also, there have been some bugs introduced in the EFI stub loader starting with the 3.7 kernel series. These bugs are causing boot failures on some computers, including some Apples. If you're using a newer kernel, therefore, you could try dropping back to a pre-3.7 kernel. Alternatively, you can swap out the EFI stub loader for an older version. (IIRC, it's just one file, but I don't remember which one offhand. I can find out if you want to try this, though.)

[propjow]

No initrd file here, but that was a good thought.

I dropped to a kernel in the 3.4 series but the issue seems to persist - the kernel halts on initial load, this time after scrambling the screen a bit.

Incidentally, I stumbled on yet another thread that suggests this particular Mini prefers a 32-bit EFI with a 64-bit kernel. So per your recommendation there I think I'll try getting a 32-bit Grub (EFI) installed to load a 64-bit kernel.

[srs5694]

Unfortunately, no EFI boot loader seems to be 100% effective. It could just be that the EFI stub loader won't work on your computer, in which case switching to another boot loader may work. For my thoughts on the various options, see my Web page on the subject. OTOH, it's also possible that you need a particular kernel option to get your system to work. Tracking that down can be difficult. The observation that you got some screen weirdness suggests you might need to set some sort of video option, though....

[ulenrich]

[propjow]