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#1: Initial revision
Likely Redis server is not running. Start with `sudo systemctl start redis-server.service` or with `sudo service redis-server start` or with `redis-server`. Check with `redis-cli` and inserting "ping" in the prompt, receiving "PONG". See for example [Redis Quickstart](https://redis.io/topics/quickstart) or [How to install and configure Redis on Ubuntu 20.04](https://www.arubacloud.com/tutorial/how-to-install-and-configure-redis-on-ubuntu-20-04.aspx).