Okay, so this whole issue got me thinking... I couldn't find a way to boot from FAT because it doesn't support blessing a file. I also couldn't find a default boot file, e.g. some bootinfo.txt or similar (boot.b, boot.bootinfo, boot.xcoff, ??) that Open Firmware would default to and use in case of FAT (with no chance to bless a file). Such filename would have to be hard-coded in OF.
It seems, the only real convenient way to go remains HFS or HFS+. Which got me thinking... We could make a /binary image/ of a pre-configured HFS partition with a version of GRUB installed and configured to search for the real configfile to use for booting on any supported filesystem (not only ext2/3/4; only limited by available GRUB file system support modules). This image could be dd'ed to a target "NewWorld Bootblock" partition, and OF would find and load the blessed GRUB on it (as pre-configured in the HFS image). This GRUB would then search for a pre-defined UUID filesystem with the real grub.cfg on it. The only thing that would have to be done during installation is to make /boot the right pre-configured UUID, so grub from the HFS binary image will load grub.cfg from it. OF3+ --> HFS NewWorld Bootblock: blessed bootinfo-style GRUB, hardcoded UUID --> finds grub.cfg on [ext2/3/4, xfs, btfs, etc. /boot] and loads it --> boot selected OS Installation steps: 1. create NewWorld Bootblock anywhere on fresh or existing HDD 2. copy binary image of pre-configured image HFS+GRUB 3. create /boot of supported fs, with UUID used in image from step 2 4. Linux only ever needs to manage grub.cfg on /boot This would transfer the need to non-free HFS utilities to be used by the package maintainer only, who has to create the NewWorld Bootblock HFS image and bless the bootinfo/GRUB2 bootloader file. The target system installing the prepared image then doesn't need to use any HFS tools... If GRUB would support something else instead of a filesystem UUID, we could also use a partition type or something similar in the pre-configured binary image for the NewWorld Bootblock HFS image... BTW, apparently this guide uses such a way also, not blessing anything on ext2, as previously (wrongly) suggested in this discussion: https://wiki.gentoo.org/wiki/GRUB_on_Open_Firmware_(PowerPC) IMHO for the OS Picker to work intuitively, an icon via a blessed bootinfo file is key... (to be included in the NewWorld Bootblock HFS image by the maintainer...) Any thoughts? Greetings, Linux User #330250 Some useful links: https://flylib.com/books/en/2.316.1.51/1/ -- The Hardware Boot Process https://flylib.com/books/en/3.126.1.47/1/ -- BootX https://lowendmac.com/2018/installing-linux-on-powerpc-macs/