Update README.md

Author: janvda

README.md

@@ -71,7 +71,10 @@ This application consist of 2 [Mosquitto MQTT-brokers](https://mosquitto.org/):
 2. **mqtt-test** which is listening to Host OS port 1884
 
 ## 7. Setup of the USB memory Stick for Influxdb
+The *influxdb* container is configured so that its data will be stored on a USB memory stick connected to the raspberry that has label `influxdb` and that is formatted in the `ext4` format as is specified in the influxdb Dockerfile.
+The script `my_entrypoint.sh` has the additional instructions to mount this USB memory stick inside the influxdb container.
 
+Note that the current *Balena* version doesn't yet support the definition of a such a mounted drive in the docker compose yaml file therefore this is handled through the influxdb container setup as described here above.
 
 ## 8. Internet access via Balena's public URL and Nginx.
 The nginx container has been configured so that when you enable the Balena public URL that you can access the following applications over the internet: