Add "How to change speedtest interval" to README

[gleniat]

This is how docker-compose.yml looks like:

speedtest:
    restart: always
    image: frdmn/speedtest-grafana:latest
    container_name: speedtest
    environment:
      - "SPEEDTEST_INTERVAL=${SPEEDTEST_SPEEDTEST_INTERVAL}"
      - "SPEEDTEST_HOST=${SPEEDTEST_HOST}"
    depends_on:
      - influxdb

1. Where does ${SPEEDTEST_SPEEDTEST_INTERVAL} come from? (.env file?)
2. How can I change the values while running via docker-compose up? Is it possible to change the interval without stopping and deleting everything and (with edited .env file) starting from scratch?

Great work by the way
Thanks

[maxiride]

Where does ${SPEEDTEST_SPEEDTEST_INTERVAL} come from? (.env file?)

Yes

How can I change the values while running via docker-compose up? Is it possible to change the interval without stopping and deleting everything and (with edited .env file) starting from scratch?

Edit the .env files and run docker-compose up -d, compose will recognize the changes and re-create the container without touching volumes.

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These are Docker issues\questions by the way, search better on the net as there are plenty of guides on the subjects you asked about.