On Tue, Jun 30, 2026 at 3:06 AM Oron Peled <[email protected]> wrote:
> On Thursday, 25 June 2026 10:19:49 IDT Vitaly Zaitsev via devel wrote: > > On 25/06/2026 08:59, Gerd Hoffmann wrote: > > > There are reasons why this is model is not used any more and > > > why UEFI firmware is able to read FAT filesystems. > > > > UEFI firmware can read any file system for which it has drivers. Fedora > > simply needs to sign the efifs package with the Fedora Secure Boot key. > > > > systemd-boot supports efifs by default. Users just need to copy the > > required driver to the EFI/systemd/drivers/ directory. > > Reading this thread shows interesting dilemma between different approaches: > * Restrict everything to FAT and get more limited but simpler boot chain > * Allow kernel+initrd in "real" filesystem, but use some "bridge" (GRUB > file systems, EFI drivers, ...) with maintenance issues. > It's unfortunate that this is the main issue that seems to have come out of this... and that anyone believes that the first approach is actually a viable choice. While I'm not going to argue about where UKIs have to be stored, we need to remember that there are other architectures than just UEFI, that there are other filesystems than FAT and there are other boot scenarios than just booting your laptop from a local (EFI) disk. > I don't see a clear "winner" strategy, so I'll bite and try to add another > kind of "bridge" for file system access. > (you are welcome to hit me hard if I'm proposing some total BS) > > What if the boot sequence would be: EFI -> "bootstrap" UKI on FAT -> load > and "kexec" real kernel from "/boot" (not necessarily FAT) > So the "bootstrap" kernel is used as an intermediate boot loader: > * It should have all needed FS drivers built in (but no > quality/maintenance issues like GRUB) > * I'm not sure it really work (e.g: can the initramfs under /boot be > loaded/executed?) > * Even if it does, I'm not sure about the gain -- would the "bootstrap" > kernel be minimal and constant enough so we can consider it as > "filesystem-access shim" ? This is not at all a bad idea, but it's also not new. ;) petitboot (on PowerPC) is a lot like this: simple loading of a minimal kernel which kexecs the "real" kernel. We actually have a PoC called nmbl [1] which is a similar idea but for UEFI (at present). nmbl is just a UKI with a GRUB menu which allows the user to either choose the running kernel or to kexec a different kernel. Unfortunately, there are problems and limitations to kexec that make it far from ideal, especially on bare metal, which is a main issue at the moment. [1] https://mlewando.fedorapeople.org/
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