efifs VS BootDuet

See also UEFI drivers that can read a bunch of other file systems (btrfs, ext2/3/4, HFS, ISO, NTFS, UFS/FFS, XFS, ZFS, etc):

* https://efi.akeo.ie

* https://github.com/pbatard/efifs

The UEFI spec specifies (§13.3) that firmware is only required to read FAT32/16/12, which is generally why your /boot/efi is VFAT/FAT32.

In theory you would still need a FAT32 efi 'stub' partition with the exFAT filesystem drivers which you have to load before loading the WinPE loader (bootmgfw.efi).

I am pretty sure that that I am doing something incorrectly with the configuration files for the rEFInd bootloader, but everything else should be correct. However, as I write this, I barely realized did I not use the following commands recommended from the "Usage" section from the aforementioned website where I downloaded the zfs_x64.efi driver file for rEFInd:

I found the drivers here https://efi.akeo.ie/ . Which means, that any EFI bootloader able to load them will be able to use them. They are not for bootloader, but it is the firmware which will use them. As i said, i am little bit afraid that it will not work on any board as some manufacturers have pretty buggy firmware when talking about infrequently used features. Also i am bit unsure they will work with secure boot as they are gpl3 thus will be never signed by Microsoft and i don't know what UEFI requirements for drivers are in this regard.

Even for those using systemd-boot with custom efi drivers to provide functionality, it's worth noting that those drivers are being developed downstream of GRUB.

I think you can also add btrfs filesystem support for sd-boot by including the EFI drivers for it on the EFI partition instead, from https://github.com/pbatard/efifs/releases I think. Haven't tried it myself though.

EFI doesn't actually mandate FAT for the system partition. The system partition can be any filesystem that the firmware supports.

Of course, pretty much all EFI implementations only support FAT, so it's a bit of a moot point; the only one I'm aware of that supports anything else is the one on Intel Macs, which also understands HFS+.

You can find a huge selection of EFI filesystem drivers at https://efi.akeo.ie/ but they're derived from GRUB and hence GPL, so don't expect the likes of American Megatrends to be bundling these any time soon.

UEFI emulation is a thing.

For people with legacy-only firmware systems, you too can run UEFI on lazy cloud providers and legacy hardware. I do this on my 14 year old dell laptop just so that all my x86_64 systems have the same boot efistub linux kernel images. All you need is to use one of the EDK DUET bootloader builds such as BootDuet¹, or for an easier user experience CloverBootloader². Only complaint is secureboot emulation can be a pain. But I imagine with Windows 11 around the corner requiring TPMs, emulators with this feature will probably get more popular.

¹ https://github.com/migle/BootDuet