Replace outdated instructions and add a tip in kubeadm-certs.md

content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-certs.md

@@ -136,7 +136,7 @@ command. In that case, you should explicitly set `--certificate-renewal=true`.
 
 ## Manual certificate renewal
 
-You can renew your certificates manually at any time with the `kubeadm certs renew` command.
+You can renew your certificates manually at any time with the `kubeadm certs renew` command, with the appropriate command line options.
 
 This command performs the renewal using CA (or front-proxy-CA) certificate and key stored in `/etc/kubernetes/pki`.
 
@@ -160,15 +160,20 @@ Name, Organization, SAN, etc.) instead of the `kubeadm-config` ConfigMap. It is
 to keep them both in sync.
 {{< /note >}}
 
-`kubeadm certs renew` provides the following options:
+`kubeadm certs renew` can renew any specific certificate or, with the subcommand `all`, it can renew all of them, as shown below:
 
-- The Kubernetes certificates normally reach their expiration date after one year.
+```shell
+kubeadm certs renew all
+```
 
-- `--csr-only` can be used to renew certificates with an external CA by generating certificate
-  signing requests (without actually renewing certificates in place); see next paragraph for more
-  information.
+{{< note >}}
+Clusters built with kubeadm often copy the `admin.conf` certificate into `$HOME/.kube/config`, as instructed in [Creating a cluster with kubeadm](https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/). On such a system, to update the contents of `$HOME/.kube/config` after renewing the `admin.conf` you must run the following commands:
 
-- It's also possible to renew a single certificate instead of all.
+```shell
+sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
+sudo chown $(id -u):$(id -g) $HOME/.kube/config
+```
+{{< /note >}}
 
 ## Renew certificates with the Kubernetes certificates API