Re: Valid grub.conf locations

[Ulrich Sibiller]

Hi,

Well, first let me say that the CentOS version has it also hardcoded and
loads the grub.conf anyway (from fw_path, I suppose). Second grub-mkimage
requires the prefix to be set, that's where it is 'hardcoded'. You cannot
run it without specifying -p. So how can I _not_ set it?

Uli



Andrei Borzenkov <arvidjaar@gmail.com> schrieb am Mo., 19. Juni 2023, 20:36:

> On 19.06.2023 19:44, Ulrich Sibiller wrote:
> > Hello,
> >
> > what exactly does "built to include networking support" mean here?
> > This non-working bootx64.efi includes many network modules, which can
> > be included using grub-mkimage (see also
> >
> https://github.com/PartialVolume/shredos.x86_64/issues/147#issuecomment-1593733621
> ):
> > ...
> > grub-mkimage: info: writing 704 bytes of a fixup block starting at
> 0x10000.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/terminal.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/gettext.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/bufio.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/boot.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/datetime.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/priority_queue.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/net.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/crypto.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/extcmd.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/normal.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/mmap.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/video.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/relocator.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/linux.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/video_fb.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/video_bochs.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/video_cirrus.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/efi_gop.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/efi_uga.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/all_video.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/archelp.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/newc.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/efinet.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/tftp.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/gcry_crc.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/gzio.mod.
> > grub-mkimage: info: reading /usr/lib/grub/x86_64-efi/part_gpt.mod.
> > grub-mkimage: info: kernel_img=0x7fd6d998b010, kernel_size=0x1c000.
> > grub-mkimage: info: the core size is 0xa03d0.
> > grub-mkimage: info: writing 0xa3000 bytes.
> >
> > But even with them included the grub.conf is only loaded from the
> > provided prefix (-p option of grub-mkimage) /EFI/BOOT. So what's
> > missing?
> >
>
> If you hardcode prefix path into core.efi, why are you surprised that
> core.efi is using this prefix? Any autodetection relies on the fact that
> prefix is *not* hardcoded.
>
> > If you run "make menuconfig in buildroot there's not much to select for
> grub2:
> >                                                      [*] grub2
> >                                                              Platform
> > (i386-pc)  --->
> >                                                        (hd0,msdos1)
> > boot partition
> >                                                       (boot linux ext2
> > fat squash4 part_msdos part_gpt normal biosdisk progress) builtin
> > modules
> >                                                       ()    builtin
> config
> >                                                        [*]   install
> tools
> >
> >
> >
> > Uli
> >
> > On Mon, Jun 19, 2023 at 4:06 PM Andrei Borzenkov <arvidjaar@gmail.com>
> wrote:
> >>
> >> On 19.06.2023 12:46, Ulrich Sibiller wrote:
> >>> Hello,
> >>>
> >>> I am wondering where grub is supposed to look for grub.cfg when booted
> >>> via PXE as grubx64.efi (or bootx64.efi)?
> >>>
> >>> Background: I have been playing around with running shredos
> >>> (https://github.com/PartialVolume/shredos.x86_64) over the network via
> >>> PXE. I failed with the bootx64.efi (which is grub2) coming with
> >>> shredos because it does not find grub.conf when booted via PXE/tftp.
> >>> It just checks /EFI/BOOT/grub.conf in this case. The grub in shredos
> >>> is built via GNU's buildroot using the official grub sources.
> >>>
> >>> So I tried with grubx64.efi as delivered by Centos7 and succeeded.
> >>> This grubx64.efi loads grub.conf - amongst other locations - from the
> >>> same path where the .efi file has been found:
> >>>
> >>> Jun 15 14:10:33 server in.tftpd[31076]: RRQ from 192.168.11.15
> >>> filename cluster/shredos/bootx64.efi
> >>> Jun 15 14:10:33 server in.tftpd[31076]: Client 192.168.11.15 finished
> >>> cluster/shredos/bootx64.efi
> >>> ...
> >>> Jun 15 14:10:40 server in.tftpd[31097]: RRQ from 192.168.11.15
> >>> filename cluster/shredos/grub.cfg
> >>> Jun 15 14:10:40 server in.tftpd[31097]: Client 192.168.11.15 finished
> >>> cluster/shredos/grub.cfg
> >>>
> >>> I think that the centos7 build works because it is patched to check
> >>> the fw_path variable. The official sources seem to not contain fw_path
> >>> at all.
> >>>
> >>> (if you want to know more details all this is described in some length
> >>> at https://github.com/PartialVolume/shredos.x86_64/issues/147)
> >>>
> >>> So is there a way to make the official grub look for grub.conf at the
> >>> same dir as the efi file when booting via PXE?
> >>>
> >>
> >> That is exactly what the official grub does when booted via PXE - as
> >> long as it was built to include networking support in the first place.
> >> And if $prefix is not hardcoded in core.efi. Without knowing how your
> >> grub binary is built it is hard to guess what could be wrong.
> >>
>
>