A new enough GRUB with osprober enabled should be able to find RPiOS, same like it does find Windows if on PC's, although I am not 100% sure.
I used Opensuse Tumbleweed a lot on RPi3 and RPI4 (64-bit, extra partitions on same SD-card) and they have created an intermediate loader in efi format that is started by the Pi firmware (bootcode.bin, start*.elf,config.txt). That binary provides then a sort of stripped UEFI and that loads then a standard ARM64 kernel. So like for UEFI Linux PC's.
If RPIOS64 is not automatically found, you can add some include file, look in /etc/grub.d or so and docs how to do that. I once did that on PC to find/boot FreeBSD.
Be aware that it matters a lot which firmware, DTBs, overlays are used. DTBs need match with kernel, which means if grub-booted as I indicate, you will mostly miss certain RPi HW features. It might be OK/better nowadays, I don't know. You also don't need RPi kernel then, just the vanilla Debian arm64 kernel.
You need to make sure your Pi uses 1 only 1 FAT filesystem to bootload. So boot preference in EEPROM or make sure there is only 1 FAT FS with file bootcode.bin on SD or USB when Pi3
A well (compiletime) configured GRUB can read from various Linux filesystems even RAID, so you only need to set the desired rootfs UUID.
I used Opensuse Tumbleweed a lot on RPi3 and RPI4 (64-bit, extra partitions on same SD-card) and they have created an intermediate loader in efi format that is started by the Pi firmware (bootcode.bin, start*.elf,config.txt). That binary provides then a sort of stripped UEFI and that loads then a standard ARM64 kernel. So like for UEFI Linux PC's.
If RPIOS64 is not automatically found, you can add some include file, look in /etc/grub.d or so and docs how to do that. I once did that on PC to find/boot FreeBSD.
Be aware that it matters a lot which firmware, DTBs, overlays are used. DTBs need match with kernel, which means if grub-booted as I indicate, you will mostly miss certain RPi HW features. It might be OK/better nowadays, I don't know. You also don't need RPi kernel then, just the vanilla Debian arm64 kernel.
You need to make sure your Pi uses 1 only 1 FAT filesystem to bootload. So boot preference in EEPROM or make sure there is only 1 FAT FS with file bootcode.bin on SD or USB when Pi3
A well (compiletime) configured GRUB can read from various Linux filesystems even RAID, so you only need to set the desired rootfs UUID.
Statistics: Posted by redvli — Sun Sep 01, 2024 1:39 pm