Hi all, As discussed in #grub irc, I think going the --boot-directory way as phcoder suggested will lead to unnecessary complexity. I would prefer directly mentioning the path to grub_prefix dir, as in case of uefi installs the prefix dir could be anything (/efi/grub, /efi/grub2, /efi/grub_custom, /efi/redhat, /efi/ubuntu etc.). Using --boot-directory in such a case also requires --bootloader-id etc. to be provided.
Proper GRUB_PREFIX is required for video.lst and locale_dir setting in grub.cfg. The patch with --prefix option is at http://pastie.org/2763921 . Please give your views.