Reboot a microVM when our agent exits

We need to upgrade Debian from stretch to buster,
since stretch's systemd doesn't support SuccessAction.

And the upgrade moves /sbin/init to /usr/sbin/init, due to
https://wiki.debian.org/UsrMerge

Signed-off-by: Kazuyoshi Kato <[email protected]>

Author: kzys

tools/image-builder/Dockerfile.debian-image

@@ -11,7 +11,7 @@
 # express or implied. See the License for the specific language governing
 # permissions and limitations under the License.
 
-FROM debian:stretch-slim
+FROM debian:buster-slim
 
 RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get -y install \

tools/image-builder/Makefile

@@ -56,7 +56,7 @@ endif
 	debootstrap \
 		--variant=minbase \
 		--include=udev,systemd,systemd-sysv,procps,libseccomp2 \
-		stretch \
+		buster \
 		"$(WORKDIR)" $(DEBMIRROR)
 	rm -rf "$(WORKDIR)/var/cache/apt/archives" \
 	       "$(WORKDIR)/usr/share/doc" \

tools/image-builder/files_debootstrap/etc/systemd/system/firecracker-agent.service

@@ -15,9 +15,9 @@ Description=Firecracker VM agent
 StartLimitIntervalSec=2
 After=local-fs.target
 Requires=local-fs.target
+SuccessAction=reboot
 
 [Service]
 Type=simple
 WorkingDirectory=/container
 ExecStart=/usr/local/bin/agent
-Restart=always

tools/image-builder/files_debootstrap/sbin/overlay-init

@@ -61,4 +61,4 @@ do_overlay
 
 # invoke the actual system init program and procede with the boot
 # process.
-exec /sbin/init $@
+exec /usr/sbin/init $@