It turns out `network-online.target` doesn't imply that there is
access to the Internet and simply using `curl --retry 10` doesn't
work and hangs forever, even if we can already reach github.com...
The User's guide is for anyone who wants to run programs and services on an exisiting Kubernetes cluster.
The Cluster Admin's guide is for anyone setting up a Kubernetes cluster or administering it.
The Developer guide is for anyone wanting to write programs that access the kubernetes API,
write plugins or extensions, or modify the core code of kubernetes.