0776112c53
On Mac rescue image is booted from HFS+ partition, so bootpath looks like /ACPI(a0341d0,0)/PCI(1,1f)/ATAPI(0,0,0)/HD(3,5d1,ca3,0000000000000000,20,0)/EndEntire grub fails to find device for this path because it cannot scan partition table. The simplest fix is to add part_apple by default.
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. Please look at the GRUB Wiki <http://grub.enbug.org> for testing procedures. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'