#!/bin/sh
# The way back to the boot image dracut made (ADR 0039, D20), as
# /etc/grub.d/41_dracut_fallback (root, 0755) on the instance's host at home, which
# update-grub runs. Ubuntu 26.04 builds its boot images with dracut, and
# dropbear-initramfs needs initramfs-tools, which replaces it: should an image of
# initramfs-tools not open the root disk, this entry boots a kernel with the image
# dracut had made for it, kept beside it as initrd.img-<version>.dracut. Chosen at the
# iMac in GRUB's menu (grub-halkyon.cfg). Once initramfs-tools' images have booted,
# the copy and this file may go.
set -e
boot=$(findmnt -no UUID /boot)
for image in /boot/initrd.img-*.dracut; do
  [ -e "$image" ] || continue
  version=${image#/boot/initrd.img-}
  version=${version%.dracut}
  [ -e "/boot/vmlinuz-$version" ] || continue
  echo "Found the way back: $version with dracut's image" >&2
  cat <<EOF
menuentry 'Ubuntu, $version with dracut (the way back)' {
	insmod part_gpt
	insmod ext2
	search --no-floppy --fs-uuid --set=root $boot
	linux /vmlinuz-$version root=/dev/mapper/ubuntu--vg-ubuntu--lv ro
	initrd /initrd.img-$version.dracut
}
EOF
done