How the GRUB on the SmileyOS USB stick is put together
======================================================

1. GRUB comes from the Ubuntu 24.04 packages grub-pc-bin and grub2-common,
   version 2.12-1ubuntu7.3, built by Ubuntu from the source in this folder:
   grub2_2.12.orig.tar.xz (GRUB 2.12) and grub2_2.12-1ubuntu7.3.debian.tar.xz
   (Ubuntu's changes and build scripts), described with their checksums in
   grub2_2.12-1ubuntu7.3.dsc. Unpack and build them with:

       dpkg-source -x grub2_2.12-1ubuntu7.3.dsc
       cd grub2-2.12 && dpkg-buildpackage -b -uc -us

2. The boot image is made with Ubuntu's own, unchanged GRUB tools:

       grub-mkimage -O i386-pc -o core.img -c early.cfg -m memdisk.tar \
           -p /boot/grub biosdisk part_msdos fat multiboot normal boot \
           configfile vbe video_bochs video_cirrus loadenv test echo serial \
           terminal gzio memdisk tar time keystatus sleep smbios

   boot.img is /usr/lib/grub/i386-pc/boot.img from grub-pc-bin, unchanged.

3. early.cfg is:

       set bootdisk=$root
       set prefix=(memdisk)/boot/grub

   memdisk.tar holds boot/grub/grub.cfg: the SmileyOS start menu, a GRUB
   configuration that picks which copy of SmileyOS on the stick to start.

GRUB's code is not changed. GRUB is free software under the GNU General
Public License, version 3 or later (GPL-3.0.txt). SmileyOS is a separate
program that GRUB starts; the GPL covers GRUB, not SmileyOS.

https://smileytech.mk/smileyos/open-source