toolchain and comments for building a custom Ubuntu distro image

zdani-build.sh

#!/bin/env bash

function init_rootfs() {
  mkdir -p rootfs scratch image/live
  sudo debootstrap focal rootfs/
}
# For how to initialize rootfs packages, see:
# https://bigdaddylinux.com/ubuntu-arch-style/

# I encountered this network-manager bug:
# https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1638842
function fix_network_manager() {
  rm rootfs/usr/lib/NetworkManager/conf.d/10-globally-managed-devices.conf
}

# First stage -- make squashfs
function make_squashfs() {
  sudo mksquashfs rootfs/ image/live/filesystem.squashfs -noappend -comp xz -Xdict-size 8k -e boot
}

# Second stage -- copy boot files to their intended locations
function copy_boot_files() {
  sudo rsync -v rootfs/boot/vmlinuz-* image/vmlinuz
  sudo rsync -v rootfs/boot/initrd.img-* image/initrd
}

# Third stage -- make both GRUB & EFI boot images
function make_bootloader() {
  sudo grub-mkstandalone --format=i386-pc --output=scratch/core.img \
    --install-modules="linux normal iso9660 biosdisk memdisk search tar ls" \
    --modules="linux normal iso9660 biosdisk search" \
    --locales="" \
    --fonts="" "boot/grub/grub.cfg=scratch/grub.cfg"
  sudo cat /usr/lib/grub/i386-pc/cdboot.img scratch/core.img >scratch/bios.img
  sudo grub-mkstandalone \
    --format=x86_64-efi \
    --output=scratch/bootx64.efi \
    --locales="" \
    --fonts="" "boot/grub/grub.cfg=scratch/grub.cfg"
  (cd scratch && dd if=/dev/zero of=efiboot.img bs=1M count=10 && mkfs.vfat efiboot.img &&
    mmd -i efiboot.img efi efi/boot && mcopy -i efiboot.img ./bootx64.efi ::efi/boot/)
}

# Fourth stage --  assemble ISO
function make_iso() {
  sudo xorriso -as mkisofs -iso-level 3 -full-iso9660-filenames -volid "Zdani" \
    -eltorito-boot boot/grub/bios.img -no-emul-boot -boot-load-size 4 -boot-info-table \
    --eltorito-catalog boot/grub/boot.cat --grub2-boot-info --grub2-mbr \
    /usr/lib/grub/i386-pc/boot_hybrid.img -eltorito-alt-boot -e EFI/efiboot.img \
    -no-emul-boot -append_partition 2 0xef scratch/efiboot.img -output "Zdani.iso" \
    -graft-points image /boot/grub/bios.img=scratch/bios.img /EFI/efiboot.img=scratch/efiboot.img
}

# Then there's nothing left to do but test
function qemu_test() {
  qemu-system-x86_64 -cdrom Zdani.iso -m 2048 -machine accel=kvm
}

function clean_rootfs() {
  echo cleaning...
  for path in rootfs/{home/zdani,root}/{.bash_history,.local,.cache}; do
    echo "Recursively delete: $path"
    sudo rm -rf "$path"
  done
  for path in rootfs/var/log/alternatives.log rootfs/var/log/apt/*.log; do
    echo "Zero over: $path"
    echo -n | sudo tee "$path"
  done
  #for home in /home/
}

# Everything after this point is just convenience & UI

function build_all() {
  clean_rootfs &&
    make_squashfs &&
    copy_boot_files &&
    make_bootloader &&
    make_iso
}

function build_boot() {
  copy_boot_files &&
    make_bootloader &&
    make_iso
}

function arch_style_chroot() {
  sudo arch-chroot rootfs
}

function usage_msg() {
  echo "Look at my source code for usage."
}

if [ "$1" == "" ]; then
  usage_msg
fi

while [ "$1" != "" ]; do
  case $1 in
  all)
    build_all
    ;;
  boot)
    build_boot
    ;;
  test)
    qemu_test
    ;;
  chroot)
    arch_style_chroot
    ;;
  *)
    usage_msg
    ;;
  esac
  shift
done