HATs and other add-ons • Re: Is A Grub-like Utility Possible With Raspberry Pi Hardware ?

As far as I know, the initial boot device source is selected by the built-in firmware and the only way to change that is to modify the boot_order.
After the boot device is chosen, the partition from which the OS is loaded from can be changed to select a different OS from that boot device. This means all OSes (or at least their boot partition) must be stored on the boot device.
The main tools to facilitate Multibooting on the Pi are PINN, MultiBoot, Berryboot, or you could handcraft a solution yourself by creating an autoboot.txt file, or selection via GPIO pins. There are also some U-boot and UEFI implementations but I am not that familiar with those.

• PINN is a fork of the original NOOBS program that is a small OS with a single program to allow installation, backup, restore, replacement & recovery of OSes. It requires MBR formatted disks, so it is restricted to disks <=2TB. OSes need to be converted to typically a tar.xz format first, but many are available. It has a graphical frontend and allows selection of the boot OS. It can also be operated remotely.
• Multiboot is a set of scripts to allow selection of multiple OSes from the same device, but I believe it is limited to Raspios-like OSes. It works by swapping the boot files. It deals with standard image files and can work with MBR and GPT disks, so it is not restricted to the 2TB limit. RonR has many scripts to allow backup and restore of images and conversion between MBR and GPT disk partitioning etc.
• Berryboot is more like PINN but uses squashfs formatted images and overlay files to avoid having multiple partitions.

To allow booting from a selectable boot device without modifying the eeprom-config would require a program to duplicate the functionality of the firmware's bootloader. I'm not aware of any that allow this.

Statistics: Posted by procount — Thu Feb 22, 2024 11:59 am

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