Problem scenario
You want to use the "docker push" command. But you do not know how your Docker host is configured. You want to know what repository your Docker host is configured to use. How do you determine which repository your "docker push" commands will be destined to?
Solution
Docker push involves a destination Docker registry -- not a repository. A registry is a collection of Docker repositories (things that hold versions of Docker images). A repository can only hold one Docker image and its different versions.
"If no registry URI is specified, Docker will assume you intend to use or log out from Docker Hub." The source of this quote is here: https://docs.joyent.com/public-cloud/instances/docker/how/get-private-docker-images
If you want to use a different registry explicitly mention it in your Docker pull command.
To not use the docker.io registry, run these commands:
docker logout- Run this command
docker login <nameOfRegistry>
If you want to push a Docker image to ECR, see "How do you upload a Docker image to Amazon Elastic Container registry?"