added logging

README.md

@@ -27,6 +27,7 @@ The included unit expects the project and its virtual environment at
 sudo useradd --system --home-dir /opt/home_control --shell /usr/sbin/nologin home-control
 sudo chown -R home-control:home-control /opt/home_control
 sudo chmod 600 /opt/home_control/service.yaml
+sudo install -d -o home-control -g home-control -m 750 /log
 sudo cp /opt/home_control/home-control.service /etc/systemd/system/
 sudo systemctl daemon-reload
 sudo systemctl enable --now home-control.service
@@ -38,3 +39,7 @@ Check its state and follow its logs with:
 sudo systemctl status home-control.service
 sudo journalctl -u home-control.service -f
 ```
+
+Confirmed arrival notifications are also appended to
+`/log/detect-arrivals.txt`. The path is configurable as
+`arrival_detection.notification.event_log`.