Use Upholds= to ensure services run after daemon-reload

When a systemd-sysext image is loaded, normally a daemon-reload is done
but the targets are not evaluated, meaning that enabled services don't
start. In Flatcar we ship a workaround for that by restarting a certain
list of targets but this is not upstream behavior. Currently upstream
also doesn't do the daemon-reload but we can file an upstream PR for
that.

convert_torcx_image.sh

@@ -32,6 +32,12 @@ for FILE in "${SYSEXTNAME}"/usr/lib/systemd/system/*.service "${SYSEXTNAME}"/usr
       -e 's,After=torcx.target,,g' -e 's,Requires=torcx.target,,g' "${FILE}"
   fi
 done
+for ENTRY in "${SYSEXTNAME}/usr/lib/systemd/system/"*.wants/*; do
+  UNIT=$(basename "${ENTRY}")
+  TARGET=$(echo "${ENTRY}" | rev | cut -d / -f 2 | rev | sed 's/.wants$//')
+  mkdir -p "${SYSEXTNAME}/usr/lib/systemd/system/${TARGET}.d"
+  { echo "[Unit]"; echo "Upholds=${UNIT}"; } > "${SYSEXTNAME}/usr/lib/systemd/system/${TARGET}.d/10-${UNIT/./-}.conf"
+done
 mkdir -p "${SYSEXTNAME}/usr/lib/extension-release.d"
 { echo "ID=flatcar" ; echo "SYSEXT_LEVEL=1.0" ; } > "${SYSEXTNAME}/usr/lib/extension-release.d/extension-release.${SYSEXTNAME}"
 rm -f "${SYSEXTNAME}".raw

create_docker_sysext.sh

@@ -64,8 +64,8 @@ if [ "${ONLY_CONTAINERD}" != 1 ]; then
 	[Install]
 	WantedBy=sockets.target
 EOF
-  mkdir -p "${SYSEXTNAME}/usr/lib/systemd/system/sockets.target.wants"
-  ln -s ../docker.socket "${SYSEXTNAME}/usr/lib/systemd/system/sockets.target.wants/docker.socket"
+  mkdir -p "${SYSEXTNAME}/usr/lib/systemd/system/sockets.target.d"
+  { echo "[Unit]"; echo "Upholds=docker.socket"; } > "${SYSEXTNAME}/usr/lib/systemd/system/sockets.target.d/10-docker-socket.conf"
   cat > "${SYSEXTNAME}/usr/lib/systemd/system/docker.service" <<-'EOF'
 	[Unit]
 	Description=Docker Application Container Engine
@@ -120,8 +120,8 @@ if [ "${ONLY_DOCKER}" != 1 ]; then
 	[Install]
 	WantedBy=multi-user.target
 EOF
-  mkdir -p "${SYSEXTNAME}/usr/lib/systemd/system/multi-user.target.wants"
-  ln -s ../containerd.service "${SYSEXTNAME}/usr/lib/systemd/system/multi-user.target.wants/containerd.service"
+  mkdir -p "${SYSEXTNAME}/usr/lib/systemd/system/multi-user.target.d"
+  { echo "[Unit]"; echo "Upholds=containerd.service"; } > "${SYSEXTNAME}/usr/lib/systemd/system/multi-user.target.d/10-containerd-service.conf"
   mkdir -p "${SYSEXTNAME}/usr/share/containerd"
   cat > "${SYSEXTNAME}/usr/share/containerd/config.toml" <<-'EOF'
 	version = 2