Valid grub.conf locations

[Ulrich Sibiller]

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?

Thanks,

Uli