For the last few days I've been working on what I call ChainBoot and wanted to share it a bit. Essencially it's just LinuxBoot (remember that?) but instead of being part of the firmware it gets loaded by your UEFI or BIOS.
I've run into the situation where I want to boot from a storage device/filesystem that wasn't supported by my BIOS (think aftermarket RAID cards or NVMe on old systems).
Of course the easy solution would've been to just install the bootloader and kernel onto a seperate drive (USB Stick or something) and boot from that while keeping the main partition on the drive.
But I thought I could do better. I remembered LinuxBoot exists and I could probably get a lot of kernel drivers to run. Then I could just use a bootloader to run LinuxBoot. In essence that's what ChainBoot is. It's a Linux kernel (with a small initrd compiled in) that can boot your system by reading the GRUB config. Even if the OS is on a storage device your BIOS wants nothing to do with.
The whole thing really was a lot simpler than I thought. Just compile Linux with a custom .config, u-root (LinuxBoot initrd) and create an iso using Limine (for non EFI environments)
I've tested it and can confirm it works. The biggest limitations are that it can't work with complex GRUB configs (e.g. some LiveCDs) and LVM (e.g. Proxmox needs to use BTRFS) but except that everything I've thrown at it booted successfully. Maybe some very minimal distros wouldn't boot since it requires a kexec compatible kernel.
Let me know what you think of it please.
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