In addition to everything else mentioned here, you might find some useful material in the Grub documentation: https://www.gnu.org/software/grub/manual/grub/gru

In addition to everything else mentioned here, you might find some useful material in the Grub documentation: https://www.gnu.org/software/grub/manual/grub/grub.html https://www.gnu.org/software/grub/manual/grub/grub.html and/or in the Linux From Scratch book: https://www.linuxfromscratch.org/lfs/read.html https://www.linuxfromscratch.org/lfs/read.html