[arch-general] The differences among bootx64.efi, loader.efi and grubx64.efi.

[Maxwell Anselm]

On Fri, Nov 15, 2019 at 8:31 AM Hongyi Zhao via arch-general <
arch-general at archlinux.org> wrote:

> Hongyi Zhao <hongyi.zhao at gmail.com> 于2019年11月15日周五 下午9:13写道：
> >
> > Ralph Corderoy <ralph at inputplus.co.uk> 于2019年11月15日周五 下午8:57写道：
> >
> > >
> > > Hi Hongyi,
> > >
> > > > I noticed that for many distro's install iso, there are some efi
> files
> > > > in the EFI/efi folder as follows:
> > > >     bootx64.efi, loader.efi and grubx64.efi
> > > >
> > > > Say, for arch:
> > > >     bootx64.efi, loader.efi
> > > >
> > > > for debian:
> > > >     bootx64.efi  grubx64.efi
> > >
> > > bootx64.efi is the default, others may exist as you can see.
> > > NVRAM defines a list to iterate over of *.efi to attempt.
> > > https://wiki.mageia.org/en/About_EFI_UEFI#The_ESP has some detail.
> > > The start of https://jdebp.eu/FGA/efi-boot-process.html may also be
> useful.
> >
> > But, I've tried use the grub2's chainloader method to invoke these efi
> > loaders, and I found that for most of the time, if both of the
> > bootx64.efi and grubx64.efi exists, the latter will have the most
> > chance to succeed, but the former often failed to boot.
> >
> > Regards
>
> The most strange thing I noticed that is the efibootmgr's arg format as
> follows:
>
> -l | --loader name     (defaults to "\EFI\/boot/EFI\grub.efi")
>
> Why it must be used like this strange form.
>
> And in the website you given here, it also gives the example like the
> flowing:
>
> sudo efibootmgr -c -d /dev/sdc -p 1 -w -L 'grub-mkstandalone-x86_64
> usb' -l \\EFI\\grub-mkstandalone\\grub-mkstandalone-x86_64.efi
>
> And this is the one I tried on my Debian/Manjaro/Ubuntu box, and it
> seems does the trick.  But I still cannot figure out why they design
> the path format like this.
>
> Regards
>
> >
> > >
> > > --
> > > Cheers, Ralph.
>

With UEFI the ESP is just a normal FAT32 partition containing executables
(with .efi extension). Those executables might be kernels, other boot
loaders, utilities, whatever. A boot entry created with efibootmgr simply
specifies how to run one of those executables on boot.

AFAIK, the only "standard" path is bootx64.efi. That is what the UEFI
standard specifies should be run if no boot entries exist. It is generally
unnecessary unless your motherboard's UEFI implementation sucks or you're
making something like a UEFI-bootable flash drive, for example.

The UEFI boot paths look weird because FAT32 uses Windows-style backslash
path separators.

Max