Re: grub-mkrescue does not boot on older Macs as USB stick

[Andrei Borzenkov <arvidjaar@gmail.com>]

22.12.2015 23:02, Andrei Borzenkov пишет:
> I tested stock grub-mkrescue on MacBook 3,1 (late 2007, Core 2 Duo) and
> iMac 9.1 (2009, same CPU) as USB stick. Neither boots; moreover,
> inserting USB stick when boot manager is shown hangs system (it stops
> reacting to mouse/keyboard); if stick is inserted during boot it never
> gets as far as even showing boot manager.
> 
> Alexander reported something similar for 2007 Macs.
> 
> Stick is not detected even when inserted under OS X. MacBook runs 10.7
> and reports that USB stick is not readable and suggests to iniitialize
> it; iMac runs 10.9 and simply ignores it (may be I do not know where to
> look).
> 
> I tried two different USB and one of them boots fine here on Dell
> Latitude E5450 as EFI so I do not think both of them are defect. Of
> course, they are not of finest quality ...
> 
> Same image as CD boots (I tried only MacBook but do not have reasons to
> think that iMac will not boot). It presents three choices - two EFI and
> one Windows. Windows ends up in presenting 1, 2 menu (without any
> additional explanation) and not accepting any input. This is known
> problem with legacy El Torito boot. First EFI boots; checking $cmdpath
> it boots from HFS+ partition. Second EFI does not boot and falls through
> to default boot order. When I try to chainload bootx64.efi manually (I
> have dual OS X/openSUSE on it) it actually boots fine. I /think/ it
> tries to load \EFI\Boot\boot.efi which is 32 bit only. I need to test
> with removed boot.efi and with fat image.
> 

It is red herring. Mac correctly loads bootx64.efi and does not need or
use startup.nsh (I do not think it even has EFI Shell which interprets
this file).

> I do not know if mkrescue image ever booted as USB on Mac. Alexander
> says it does on modern Mac; anyone ever tried it on earlier models?
> 

OK, it turned out to be not related to xorriso, but for the record ...

Mac does not like FAT created by mformat. I can reproduce it easily by
creating single MSDOS partition on USB stick of type 0xef size 2880K,
formatting it with same options as grub-mkrescue:

sudo mformat -C -f 2880 -L 16 -i /dev/sdb1 ::

and copying bootx64.efi into \EFI\BOOT on it.

The same partition formatted with mkfs -t fat works like a charm.

Both Porteus and openSUSE CD (which correctly boot) have ESP created by
mkfs.fat.

TBH I think that precreating FAT once and shipping image with GRUB is
the most simple solution. It can be empty, we can dd files later.

Ideas?