After docker installed, it is recommended to check it with below command:
sudo docker run hello-world
When it fails to run, it might be a missing proxy configuration. Docker has its own proxy configuration and it does not use http_proxy variable.
Define docker proxy:Edit etc/systemd/system/docker.service.d/http-proxy.conf and add proxy under [Service] section:
Environment="http_proxy=http://PROXY_MACHINE_REAL_NAME:8080" "https_proxy=http://PROXY_MACHINE_REAL_NAME:8080" "no_proxy=127.0.0.1,localhost,mydyumserver"