issue 1841/S15: put the booted kernel first when GRUB's menu is generated again, so the fallback kernel, sorted first by version, never becomes the default entry (ADR 0508 §9)

2026-10-22 17:49:21 +02:00
parent f40269caec
commit 76a0a726f0
3 changed files with 54 additions and 5 deletions
@@ -104,8 +104,30 @@ grub)
 	if [ "$menu" = "$have" ]; then
 		echo "grub: the menu lists the kernels in /boot, left as it is"
 	else
-		grub-mkconfig -o "$cfg"
-		echo "grub: the kernels in /boot changed ($(echo $have | tr '\n' ' ')); the menu is generated again; the default entry is as it was"
+		# GRUB lists kernels in reverse version order, so the fallback kernel would come first and become the
+		# default entry: the kernel the machine booted is put first (GRUB_TOP_LEVEL; /etc/default/grub still
+		# overrides it when it sets one), the fallback kernel never.
+		top=$(tr ' ' '\n' <"$root/proc/cmdline" | sed -n 's|^BOOT_IMAGE=\(.*\)$|\1|p' | head -n 1)
+		top=$(printf '%s' "$top" | sed 's|.*/||')
+		case "$top" in
+		vmlinuz-linux-lts | "") top= ;;
+		esac
+		[ -n "$top" ] && [ -e "$boot/$top" ] || top=
+		if [ -z "$top" ]; then
+			if [ -e "$boot/vmlinuz-linux" ]; then
+				top=vmlinuz-linux
+			else
+				top=$(printf '%s\n' $have | grep -v '^vmlinuz-linux-lts$' | head -n 1 || true)
+			fi
+		fi
+		if [ -n "$top" ]; then
+			GRUB_TOP_LEVEL=/boot/$top grub-mkconfig -o "$cfg"
+		else
+			grub-mkconfig -o "$cfg"
+		fi
+		first=$top
+		[ -n "$first" ] || first="the menu's own order"
+		echo "grub: the kernels in /boot changed ($(echo $have | tr '\n' ' ')); the menu is generated again with $first first; the default entry is as it was"
 	fi
 	;;
 esac