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> Date: Mon, 8 Jun 2015 11:24:20 +0200
> From: george@nsup.org
>
> More precisely: a conforming UEFI firmware MUST be able to read FAT32
> partitions. It CAN be able to read other types: apple's implementation can
> read apple's proprietary filesystem.
>
> If you KNOW that YOUR firmware supports ext2, you can use ext2. More likely,
> your firmware only supports FAT32, possibly NTFS.
>
Ah, I did not know that the EFI spec didn't mandate FAT32 for the ESP.
>> Its partition type in gdisk should be EF00,
>> and it should be mounted on /boot/efi.
>
> Not much. It should be mounted there if you want to use grub-install with
> the default options, and probably a few other similar tools, but that is
> all.
Well, default options are default options. Debian tools expect the ESP
to be mounted at /boot/efi. That's enough of a "should" for me. Debian
has always provided ways to deviate from the default setup, but that
doesn't alter the premise.
>
>> [ESP] is required to be present when using EFI boot.
>
> This is not true at all.
>
> When using UEFI boot, you need a bootloader on a supported filesystem in a
> supported partition, pointed by the UEFI variables for the menu. The GPT
> type of the partition is irrelevant.
Yet, the EFI spec only requires the firmware to support FAT32...
> You need an UEFI system partition with the precise characteristics if you
> want your firmware to GUESS the bootloader to use on the device, without a
> boot variable pointing to it.
...and the EFI firmware only looks for bootloaders in a partition of
type 0xEF or C12A7328-F81F-11D2-BA4B-00A0C93EC93B.
That you can find ways to configure your UEFI system to boot without
a partition of that specific type doesn't invalidate my statement
though. The spec mandates a discoverable partition, and it wouldn't
surprise me if half of the firmwares out there would flatly refuse to read
files from a partition with the wrong type.
>> (which we already knew, as Windows does not support booting in EFI mode
>> from an MBR-style disk)
>
> I am no windows specialist, but I doubt this is true: I have observed a
> barely-conforming laptop without BIOS emulation booting a windows 8 recovery
> USB stick formated in MBR format.
>From https://msdn.microsoft.com/en-us/library/windows/hardware/dn336946.aspx:
[..] you receive the error message: "Windows cannot be installed to
this disk. The selected disk is not of the GPT partition style", it's
because your PC is booted in UEFI mode, but your hard drive is not
configured for UEFI mode. You’ve got a few options:
- Reboot the PC in legacy BIOS-compatibility mode. This option lets
you keep the existing partition style. [..]
- Reformat the drive for UEFI by using the GPT partition style. This
option lets you use the PC’s UEFI firmware features.
Regards,
Arno
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