1 files changed, 89 insertions, 0 deletions
diff --git a/installer/configure-target-grub.sh b/installer/configure-target-grub.sh
new file mode 100755
index 0000000..2f16692
--- /dev/null
+++ b/installer/configure-target-grub.sh
@@ -0,0 +1,89 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+target_root=${1:?usage: configure-target-grub.sh TARGET_ROOT}
+
+if [[ ! -d "${target_root}/etc" || ! -d "${target_root}/usr" ]]; then
+  echo "Invalid target root: ${target_root}" >&2
+  exit 1
+fi
+
+grub_defaults="${target_root}/etc/default/grub"
+mkdir -p "$(dirname "${grub_defaults}")"
+
+if [[ -f "${grub_defaults}" ]] && grep -q '^GRUB_TIMEOUT=' "${grub_defaults}"; then
+  sed -i 's/^GRUB_TIMEOUT=.*/GRUB_TIMEOUT=0/' "${grub_defaults}"
+else
+  printf 'GRUB_TIMEOUT=0\n' >> "${grub_defaults}"
+fi
+
+grub_editenv=""
+for candidate in \
+  "${target_root}/usr/bin/grub2-editenv" \
+  "${target_root}/usr/sbin/grub2-editenv"; do
+  if [[ -x "${candidate}" ]]; then
+    grub_editenv="${candidate#"${target_root}"}"
+    break
+  fi
+done
+
+grub_mkconfig=""
+for candidate in \
+  "${target_root}/usr/bin/grub2-mkconfig" \
+  "${target_root}/usr/sbin/grub2-mkconfig"; do
+  if [[ -x "${candidate}" ]]; then
+    grub_mkconfig="${candidate#"${target_root}"}"
+    break
+  fi
+done
+
+if [[ -z "${grub_editenv}" || -z "${grub_mkconfig}" ]]; then
+  echo "The target image does not contain the required GRUB tools" >&2
+  exit 1
+fi
+
+mounted_paths=()
+cleanup() {
+  local path
+  for path in "${mounted_paths[@]}"; do
+    umount -R "${path}" 2>/dev/null || true
+  done
+}
+trap cleanup EXIT
+
+bind_runtime_tree() {
+  local source=$1
+  local destination="${target_root}/${source#/}"
+
+  mkdir -p "${destination}"
+  if mountpoint -q "${destination}"; then
+    return 0
+  fi
+
+  mount --rbind "${source}" "${destination}"
+  mount --make-rslave "${destination}"
+  mounted_paths+=("${destination}")
+}
+
+# grub2-mkconfig invokes grub-probe and needs the installer's device and EFI
+# views while it runs inside the installed image.
+bind_runtime_tree /dev
+bind_runtime_tree /proc
+bind_runtime_tree /sys
+
+chroot "${target_root}" "${grub_editenv}" - set menu_auto_hide=1
+
+if [[ -e "${target_root}/etc/grub2-efi.cfg" || -L "${target_root}/etc/grub2-efi.cfg" ]]; then
+  grub_config=/etc/grub2-efi.cfg
+elif [[ -e "${target_root}/etc/grub2.cfg" || -L "${target_root}/etc/grub2.cfg" ]]; then
+  grub_config=/etc/grub2.cfg
+elif [[ -d /sys/firmware/efi ]]; then
+  grub_config=/etc/grub2-efi.cfg
+else
+  grub_config=/etc/grub2.cfg
+fi
+
+chroot "${target_root}" "${grub_mkconfig}" -o "${grub_config}"
+
+echo "Configured target GRUB: GRUB_TIMEOUT=0, menu_auto_hide=1, ${grub_config}"