kubeadm: improve links and information around using the config file

- Add link from the kubeadm-config page to the paragraphs on
using "--config" with "init" and "join".
- Improve text in the the paragraphs on using "--config" with
"init" and "join".
- Reword the link about the configuration file in the
create-cluster-kubeadm page.

content/en/docs/reference/setup-tools/kubeadm/kubeadm-config.md

@@ -16,6 +16,10 @@ You can use `kubeadm config print` to print the default configuration and `kubea
 convert your old configuration files to a newer version. `kubeadm config images list` and
 `kubeadm config images pull` can be used to list and pull the images that kubeadm requires.
 
+For more information navigate to
+[Using kubeadm init with a configuration file](/docs/reference/setup-tools/kubeadm/kubeadm-init/#config-file)
+or [Using kubeadm join with a configuration file](/docs/reference/setup-tools/kubeadm/kubeadm-join/#config-file).
+
 In Kubernetes v1.13.0 and later to list/pull kube-dns images instead of the CoreDNS image
 the `--config` method described [here](/docs/reference/setup-tools/kubeadm/kubeadm-init-phase/#cmd-phase-addon)
 has to be used.

content/en/docs/reference/setup-tools/kubeadm/kubeadm-init.md

@@ -114,16 +114,18 @@ The config file is still considered beta and may change in future versions.
 
 It's possible to configure `kubeadm init` with a configuration file instead of command
 line flags, and some more advanced features may only be available as
-configuration file options. This file is passed with the `--config` option.
+configuration file options. This file is passed using the `--config` flag and it must
+contain a `ClusterConfiguration` structure and optionally more structures separated by `---\n`
+Mixing `--config` with others flags may not be allowed in some cases.
 
 The default configuration can be printed out using the
 [kubeadm config print](/docs/reference/setup-tools/kubeadm/kubeadm-config/) command.
 
-It is **recommended** that you migrate your old `v1beta1` configuration to `v1beta2` using
+If your configuration is not using the latest version it is **recommended** that you migrate using
 the [kubeadm config migrate](/docs/reference/setup-tools/kubeadm/kubeadm-config/) command.
 
-For more details on each field in the `v1beta2` configuration you can navigate to our
+For more information on the fields and usage of the configuration you can navigate to our API reference
-[API reference pages](https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2).
+page and pick a version from [the list](https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm#pkg-subdirectories).
 
 ### Adding kube-proxy parameters {#kube-proxy}
 

content/en/docs/reference/setup-tools/kubeadm/kubeadm-join.md

@@ -273,15 +273,17 @@ The config file is still considered beta and may change in future versions.
 It's possible to configure `kubeadm join` with a configuration file instead of command
 line flags, and some more advanced features may only be available as
 configuration file options. This file is passed using the `--config` flag and it must
-contain a `JoinConfiguration` structure.
+contain a `JoinConfiguration` structure. Mixing `--config` with others flags may not be
+allowed in some cases.
 
-To print the default values of `JoinConfiguration` run the following command:
+The default configuration can be printed out using the
+[kubeadm config print](/docs/reference/setup-tools/kubeadm/kubeadm-config/) command.
 
-```shell
+If your configuration is not using the latest version it is **recommended** that you migrate using
-kubeadm config print join-defaults
+the [kubeadm config migrate](/docs/reference/setup-tools/kubeadm/kubeadm-config/) command.
-```
 
-For details on individual fields in `JoinConfiguration` see [the godoc](https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm#JoinConfiguration).
+For more information on the fields and usage of the configuration you can navigate to our API reference
+page and pick a version from [the list](https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm#pkg-subdirectories).
 
 ## {{% heading "whatsnext" %}}
 

content/en/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm.md

@@ -139,7 +139,7 @@ is not supported by kubeadm.
 
 For more information about `kubeadm init` arguments, see the [kubeadm reference guide](/docs/reference/setup-tools/kubeadm/kubeadm/).
 
-For a complete list of configuration options, see the [configuration file documentation](/docs/reference/setup-tools/kubeadm/kubeadm-init/#config-file).
+To configure `kubeadm init` with a configuration file see [Using kubeadm init with a configuration file](/docs/reference/setup-tools/kubeadm/kubeadm-init/#config-file).
 
 To customize control plane components, including optional IPv6 assignment to liveness probe for control plane components and etcd server, provide extra arguments to each component as documented in [custom arguments](/docs/setup/production-environment/tools/kubeadm/control-plane-flags/).