<p>I've an EKS cluster in AWS.</p>
<pre><code>[cloudshell-user@ip-10-0-87-109 ~]$ kubectl version --short
Kubeconfig user entry is using deprecated API version client.authentication.k8s.io/v1alpha1. Run 'aws eks update-kubeconfig' to update.
Client Version: v1.23.7-eks-4721010
Server Version: v1.20.11-eks-f17b81
</code></pre>
<pre><code>[cloudshell-user@ip-10-0-87-109 ~]$ kubectl get nodes
Kubeconfig user entry is using deprecated API version client.authentication.k8s.io/v1alpha1. Run 'aws eks update-kubeconfig' to update.
NAME                    STATUS   ROLES    AGE     VERSION
fargate-172.101.0.134   Ready    &lt;none&gt;   13d     v1.20.15-eks-14c7a48
fargate-172.101.0.161   Ready    &lt;none&gt;   68d     v1.20.15-eks-14c7a48
</code></pre>
<p>On Nov 1st AWS is going to update the server version to 1.21 because AWS going to end the support of 1.20.</p>
<p>What problems will come up? I read</p>
<blockquote>
<p>no EKS features were removed in 1.21</p>
</blockquote>
<p>What should I do in order to be safe?</p>

Luca Rasconi
<p>You do not really need to perform any safety checks on your end, AWS will take care of the upgrade process (at least from <code>20</code> to <code>21</code>. My recommendation will be to upgrade before AWS tries to upgrade the cluster, as once it reached the end of life, the upgrade can happen anytime</p>
<p>The only thing you need to update manually</p>
<ul>
<li>Self-managed Node Group</li>
<li>Any add-on</li>
</ul>
<p>The <strong>breaking change</strong> is the <a href="https://github.com/kubernetes/enhancements/issues/542" rel="nofollow noreferrer">service account token expiry</a></p>
<ul>
<li>Any service that depends on a service token account, keep in mind that now the token will expire in one hour and the service/pod need to refresh the token</li>
</ul>
<blockquote>
<p>Service account tokens now have an expiration of one hour. In previous Kubernetes versions, they didn't have an expiration.</p>
</blockquote>
<blockquote>
<p>On the end of support date, you can no longer create new Amazon EKS clusters with the unsupported version. Existing control planes are automatically updated by Amazon EKS to the earliest supported version through a gradual deployment process after the end of support date. <strong>After the automatic control plane update, make sure to manually update cluster add-ons and Amazon EC2 nodes</strong>.</p>
</blockquote>
<p><a href="https://docs.aws.amazon.com/eks/latest/userguide/kubernetes-versions.html#kubernetes-1.21" rel="nofollow noreferrer">kubernetes-versions-1.21</a></p>
