If you want to pull container-images from an insecure registry over http instead of https, you have to specify the registry as insecure. Otherwise docker will refuse, because of the unencrypted connection.

To do so open the config file /etc/docker/daemon.json. If it does not exist, simply create one.

Inside you will specify the registry like so.

/etc/docker/daemon.json

{
    "insecure-registries": ["my-registry.local:5000"]
}

For the changes to take affect, you need to restart the docker-daemon.

This will restart your containers as well and will cause downtime!

[tux@server]$ sudo systemctl restart docker

After that you can pull and push images without an error.