rootfs-builder: fix unbootable dracut-based initramfs on Fedora

This is a forward port of Kata 1.x PR's
https://github.com/kata-containers/osbuilder/pull/480 and
https://github.com/kata-containers/osbuilder/pull/494 .

Fixes #646

Signed-off-by: Pavel Mores <pmores@redhat.com>

tools/osbuilder/image-builder/image_builder.sh

@@ -186,14 +186,20 @@ check_rootfs() {
 	OK "init is installed"
 
 
-	systemd_path="/lib/systemd/systemd"
+	candidate_systemd_paths="/usr/lib/systemd/systemd /lib/systemd/systemd"
-	systemd="${rootfs}${systemd_path}"
 
 	# check agent or systemd
 	case "${AGENT_INIT}" in
 		"no")
-			if [ ! -x "${systemd}" ] && [ ! -L "${systemd}" ]; then
+			for systemd_path in $candidate_systemd_paths; do
-				error "${systemd_path} is not installed in ${rootfs}"
+				systemd="${rootfs}${systemd_path}"
+				if [ -x "${systemd}" ] || [ -L "${systemd}" ]; then
+					found="yes"
+					break
+				fi
+			done
+			if [ ! $found ]; then
+				error "None of ${candidate_systemd_paths} is installed in ${rootfs}"
 				return 1
 			fi
 			OK "init is systemd"
@@ -207,10 +213,13 @@ check_rootfs() {
 				return 1
 			fi
 			# checksum must be different to system
-			if [ -f "${systemd}" ] && cmp -s "${systemd}" "${agent}"; then
+			for systemd_path in $candidate_systemd_paths; do
-			   error "The agent is not the init process. ${agent_path} is systemd"
+				systemd="${rootfs}${systemd_path}"
-			   return 1
+				if [ -f "${systemd}" ] && cmp -s "${systemd}" "${agent}"; then
-			fi
+					error "The agent is not the init process. ${agent_path} is systemd"
+					return 1
+				fi
+			done
 
 			OK "Agent installed"
 			;;

tools/osbuilder/rootfs-builder/rootfs.sh

@@ -441,8 +441,7 @@ prepare_overlay()
 	# we were passed a pre-populated rootfs directory
 	if [ ! -e ./sbin/init ]; then
 		ln -sf  ./usr/lib/systemd/systemd ./init
-		ln -sf  ../../init ./lib/systemd/systemd
+		ln -sf  /init ./sbin/init
-		ln -sf  ../init ./sbin/init
 	fi
 
 	# Kata systemd unit file