GRUB compile from source on Linux - Linux Tutorial

GRUB is the acronym for GNU GRand Unified Bootloader: it is the bootloader used in practically all Linux distributions out there. Early in the boot stage, the bootloader is loaded by the machine firmware, either BIOS or UEFI (GRUB supports both of them), and it loads one of the available kernels. Being an essential software, grub is installed by default and available in the official repositories of distribution we are using; sometimes, however, we may want compile GRUB from source, either to obtain a specific version of it or to circumvent the modification the distributions could have made to the vanilla code. In this tutorial we see how to perform such operation.

This is a companion discussion topic for the original entry at

IT would be nice to explain what impact configure options have. If platform is EFI, can Grub boot legacy system as well? If it is i386, will it boot EFI? If not, how it comes that distribution GRUB is quite universal? When will Grub mount come handy?