Grub2 (Efi) boot via PXE - load config file automatically

I´ve got a problem booting my OS via Grub2 bootloader.

Environment:

I´ve got a PXE-Boot Infrastructure and want to test PXE-Booting Grub2.efi via Network (TFTP).

Downloading the efi-file to the client works and grub gets loaded on the machine - I can see the grub prompt grub> - I´m using Grub Version 2.00.

I´ve created a config file (grub.cfg) and placed it in the same TFTP-Directory as the grub.efi file.

I can see from the TFTP-logs that GRUB gets downloaded - and obviously loaded on the client - and afterwards the grub.cfg get downloaded by grub.

My grub.cfg looks as follows:

set root=(hd0,gpt1)
chainloader (${root})/EFI/Microsoft/Boot/bootmgfw.efi
boot

Minimalistically I just want to boot Windows with GRUB. Please don´t ask why; that would take too long to describe…

I would expect GRUB to find the downloaded grub.cfg file and load Windows.

What happens: I just get thrown to the grub> prompt.

When I load the grub.cfg from the grub prompt via

configfile /grub.cfg

the OS gets loaded perfectly, so that seems to be OK so far.

So my problem is, how can I get GRUB to automatically load the config file and boot Windows?

2 Answers

Grub looks for a config file /grub/grub.cfg or /grub/x86_64-efi/grub.cfg (or similar).

NB: It is a path from the TFTP server root. That means even if you run your Grub binary from a path like $tftproot/path/to/grubnetx64.efi, don't try to put the direcotry grub/ to the same directory, but really to your TFTP root: $tftproot/grub/

How to find out

In the Grub console:

grub> cat (memdisk)/grub.cfg
if [ -e $prefix/x86_64-efi/grub.cfg ]; then source Sprefix/x86_64-efi/grub.cfg
else source Sprefix/grub.cfg
fi

And the important part, what the $prefix is:

grub> echo $prefix
(tftp,x.x.x.x)/grub

Make it in a menuentry and set default="0".

Reference: wiki.ubuntu.com - UEFI/PXE-netboot-install