I have a booting USB stick with some iso-image, based on Arch Linux. It loads through efi and then comes to Grub 1.99, where I can choose the iso images. I can load them without any problems, but before I see the menu of the Grub some error messages appear:

error: "prefix" is not set

error: efidisk read error

USB stick is formatted in FAT32 and has a partition table msdos.

Here is my /boot/grub/grub.cfg

insmod video
insmod font
insmod jpeg

insmod gfxterm

set prefix=/boot/grub/grub.cfg

loadfont /boot/grub/unicode.pf2

set gfxmode=auto
terminal_output gfxterm

background_image /boot/grub/background.jpg
set default=0

set timeout=10

set menu_color_normal=white/black set menu_color_highlight=black/light-gray

menuentry "image.iso" {
set isofile="/images/image.iso" loopback loop $isofile set root=(loop) linux /isolinux/vmlinuz isofile=$isofile splash quiet initrd /isolinux/initrd }

These settings works without any problems. At least, I can see my background image and the styles has been changed.

I also checked from the Grub shell the parameters

root=hd2,msdos1 //means that I have a correct path, otherwise actually it doesn't boot.

I tried different versions of this prefix // /boot/grub/ // /boot/grub/grub.cfg // /efi/boot/

I would be glad to hear what can be the problem:)

p.s. Was reading also that can be sth with GPT partition table, but in this case it doesn't boot with my computer.

Thanks for helping.

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