Hi, i plan to ask at gru-devel about mformat, its MBR, and the partition entry, as soon as the last experiment is made (LBA 1 rather than LBA 0 as start of the inner partition).
For that discussion i could also need the exact model name of the Macbook. If its EFI has a name, then this too. Florian Pelz wrote: > +--- grub-2.02/util/grub-mkrescue.c 2019-04-21 08:17:18.880000000 +0200 > ++++ grub-2.02/util/grub-mkrescue.c 2019-04-21 08:17:52.588000000 +0200 > [...] > +- { "mformat", "-C", "-f", "2880", "-L", "16", > ++ { "mformat", "-k", "-C", "-f", "2880", "-L", "16", The difference between the contents of the first image block with and without option -k is significant, at least if we ask program "file". If a special version of gub-mkrescue is acceptable, then i would rather propose to apply the dd treatment to efiimgfat after mformat created it without option -k. We could ask at grub-devel for advise how to write 16 bytes to that file without needing another shell command. (It's C language, after all.) The binary differences between both blocks 0, except partition entry, are: /efi.img from Guix 0.16.0 ######################### Image from mformat -k 00000000 : eb 3c 90 4d 54 4f 4f 34 30 32 31 00 02 01 01 00 ### ### ### ### ### ### ### ### ### ### ### 00000000 : 00 00 00 00 00 00 00 00 00 00 00 00 02 01 01 00 00000020 : 00 00 00 00 00 00 29 a7 48 66 33 4e 4f 20 4e 41 ### ### ### ### 00000020 : 00 00 00 00 00 00 29 42 87 4b 7d 4e 4f 20 4e 41 00000030 : 4d 45 20 20 20 20 46 41 54 31 32 20 20 20 fa 31 ### ### 00000030 : 4d 45 20 20 20 20 46 41 54 31 32 20 20 20 00 00 00000040 : c0 8e d8 8e c0 fc b9 00 01 be 00 7c bf 00 80 f3 ### ### ### ### ### ### ### ### ### ### ### ### ### 00000040 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000050 : a5 ea 56 00 00 08 b8 01 02 bb 00 7c ba 80 00 b9 ### ### ### ### ### ### ### ### ### ### ### ### 00000050 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00000060 : 01 00 cd 13 72 05 ea 00 7c 00 00 cd 19 00 00 00 ### ### ### ### ### ### ### ### ### 00000060 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ... 000001f0 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa ### ### 000001f0 : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Have a nice day :) Thomas