Certbot should attempt to renew certificates daily

Makefile

-all:
+all: certbot-timer certbot-service
 	tar xf certbot-1.3.0.tar.gz
 	install -v -Dm755 certbot-1.3.0/certbot-auto /usr/bin/certbot-auto
 	install -v -m755 -d /etc/letsencrypt
 	USE_PYTHON_3=1 certbot-auto --install-only --no-bootstrap --no-self-upgrade
+
+	@echo "$$CERTBOT_TIMER" > /lib/systemd/system/certbot.timer
+	@echo "$$CERTBOT_SERVICE" > /lib/systemd/system/certbot.service
+	systemctl enable certbot.timer
+
+certbot-timer:
+define CERTBOT_TIMER
+[Unit]
+Description=Renew certificates periodically
+
+[Timer]
+OnCalendar=daily
+Persistent=true
+
+[Install]
+WantedBy=timers.target
+endef
+export CERTBOT_TIMER
+
+certbot-service:
+define CERTBOT_SERVICE
+[Unit]
+Description=Renew certificates
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/certbot-auto --no-self-upgrade renew
+endef
+export CERTBOT_SERVICE