diff --git a/rootf-kernel/Makefile b/rootf-kernel/Makefile
index 5e5425f..28cbcd3 100644
--- a/rootf-kernel/Makefile
+++ b/rootf-kernel/Makefile
@@ -7,11 +7,10 @@ use-arch: ../out/arch-rootfs.ext4
 use-alpine: ../out/alpine-rootf.ext4
 	ln -s $< ../out/rootfs.ext4
 
-use-ubuntu: ../out/ubuntu-22.04.ext4
+use-ubuntu: ../out/ubuntu-22.04.ext4 ../out/ubuntu-22.04.id_rsa
 	ln -s $< ../out/rootfs.ext4
 
 
-
 ../out/arch-rootfs.ext4:
 	bash ./arch-rootf.sh
 
@@ -20,3 +19,7 @@ use-ubuntu: ../out/ubuntu-22.04.ext4
 
 ../out/ubuntu-22.04.ext4:
 	wget -O $@ https://s3.amazonaws.com/spec.ccfc.min/firecracker-ci/v1.7/$$(uname -m)/ubuntu-22.04.ext4
+
+../out/ubuntu-22.04.id_rsa:
+	wget -O $@ https://s3.amazonaws.com/spec.ccfc.min/firecracker-ci/v1.7/$$(uname -m)/ubuntu-22.04.id_rsa
+	chmod 400 $@