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Re: phantom drives in GRUB on Apple Macbook Pro

From: Chris Murphy
Subject: Re: phantom drives in GRUB on Apple Macbook Pro
Date: Sat, 30 Nov 2019 13:41:22 -0700

On Sat, Nov 30, 2019 at 11:47 AM Toomas Soome via Grub-devel
<address@hidden> wrote:

> APFS is not just stand alone partition, APFS is container for subvolumes 
> (vendor media paths) - like having partition table inside the partition. It 
> sounds like grub is sorting them out wrong.

Perhaps. But I'd expect the firmware pre-boot environment can become
aware of the container nature of APFS only if an APFS driver is
loaded. Based on the "EFI jumpstart" description in the Apple File
System Reference, I'm not sure if it is:

"A partition formatted using the Apple File System contains an
embedded EFI driver thatʼs used to boot a machine from
that partition."

That section describes the minimal steps needed to locate and load
Apple's APFS EFI driver from within an APFS formatted partition. It's
plausible that this jumpstart is skipped if the first boot entry in
NVRAM is not APFS, and the referenced EFI file is found and loadable -
which is the case in this situation. NVRAM first boot entry points to
grubx64.efi. And even if an APFS EFI driver is loaded, I'm not sure if
GRUB's ls command is expected to be able to read APFS volumes and

When I do 'ls (hdX)/' I consistently get an error from
efidisk.c:602:failure reading sector 0x80 for each of hd0, hd1, hd2,
hd3. For hd4 I get a different error which is fs.c:120:unknown file

Chris Murphy

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