Hi,
> AFAICS we would need to build grub > twice, for pc-i386 and efi-x86-64. Well, yes. But then it boots everywhere. Debian normally uses i386-pc and the *-efi which matches the "architecture" of the ISO: "i386", "amd64". A grub-mkrescue ISO for i386-pc, x86_64-efi, and i386-efi with no operating system payload looks like this: $ du 1334 ./boot/grub/fonts 1927 ./boot/grub/i386-efi 2031 ./boot/grub/i386-pc 3114 ./boot/grub/locale 2 ./boot/grub/roms 2606 ./boot/grub/x86_64-efi 11015 ./boot/grub 11017 ./boot 230 ./System/Library/CoreServices 232 ./System/Library 234 ./System 14134 . $ ls -l dr-xr-xr-x 1 root root 2048 Feb 6 2016 System dr-xr-xr-x 1 root root 2048 Feb 6 2016 boot -r--r--r-- 1 root root 2048 Feb 6 2016 boot.catalog -r--r--r-- 1 root root 2949120 Feb 6 2016 efi.img -r--r--r-- 1 root root 0 Dec 24 2015 empty-file.txt -r--r--r-- 1 root root 0 Feb 6 2016 mach_kernel The EFI System Partition content: # mount /mnt/iso/efi.img /mnt/fat $ cd /mnt/fat $ ls -lR .: total 3 -rwxr-xr-x 1 root root 1759 Dec 10 2017 NvVars drwxr-xr-x 3 root root 1024 Feb 6 2016 efi ./efi: total 1 drwxr-xr-x 2 root root 1024 Feb 6 2016 boot ./efi/boot: total 318 -rwxr-xr-x 1 root root 95744 Feb 6 2016 boot.efi -rwxr-xr-x 1 root root 95744 Feb 6 2016 bootia32.efi -rwxr-xr-x 1 root root 132608 Feb 6 2016 bootx64.efi This is about the maximum of useful boot equipment. The two EFI startup programs can share one partition. So the options or commands proposed by me stay valid, if EFI is involved at all. The FAT image looks vastely oversized, mimicking a 2.8 MB floppy: $ df /mnt/fat Filesystem 1K-blocks Used Available Use% Mounted on /dev/loop1 2863 322 2541 12% /mnt/fat There is no reference to floppies in EFI specs. 500 KB of FAT filesystem should fully suffice here. (Guix ISOs had problems with this kind of cargo cult, because mformat on behalf of grub-mkrescue inserts a partition table into the image. Some antique EFI began to loop on it infinitely, because partition 1 starts at block 0.) If you do not want PC-BIOS support in the ISO, then simply leave out the xorrisofs option -b (or its xorriso native equivalent) and the El Torito separator option -eltorito-alt-boot before you use option -e. > I was considering pc-i386 for 32bit x86 builds There is an increasing number of reports about EFI-only notebook PCs. I am not sure whether there are 32-bit systems among them. Surely there are 32-bit EFI firmwares out there. > and efi-x86-64 for x86-64 builds I have a PC-BIOS-only 64-bit AMD test machine from 2010: Desktop, 4 x 2.4 GHz, 4 GB RAM, 500 GB disk. Hosts Debian 6, FreeBSD 8, Solaris for legacy regression testing. (And served me already two times as fallback for a few days, when my workstation hardware curled its toes.) Even with younger 64-bit machines it might be convenient for testers if they do not have to change the EFI legacy settings before booting the ISO. Have a nice day :) Thomas ----------------------------------------------------------- If you wish to unsubscribe from this mailing, send mail to [email protected] with a subject of: unsubscribe t2
