Upgrading the Kubernetes master involves the simple step of specifying your EKS name and desired new version, as shown in the following. This takes around 30 minutes to complete, based on the condition. Meanwhile, accessing Kubernetes API server (via kubectl) might fail. Although pods and Services won't be affected, you need to leave enough time to perform this operation:

$ aws eks update-cluster-version --name chap10 --kubernetes-version 1.11
{
    "update": {
        "status": "InProgress", 
        "errors": [], 
        "params": [
            {
                "type": "Version", 
                "value": "1.11"
            }, 
            {
                "type": "PlatformVersion", 
                "value": "eks.1"
            }
        ], 
        "type": "VersionUpdate", 
        "id": "09688495-4d12-4aa5-a2e8-dfafec1cee17", 
        "createdAt": 1545007011.285
    }
}

As you can see in the preceding code, the aws eks update-cluster-version command returns update id. You can use this ID to check the upgrade status, as follows:

$ aws eks describe-update --name chap10 --update-id 09688495-4d12-4aa5-a2e8-dfafec1cee17
{
    "update": {
        "status": "InProgress", 
        "errors": [], 
...
...

Once the status changes from InProgress to Successful, you can see the newer version of the API server as follows:

$ kubectl version --short
Client Version: v1.10.7
Server Version: v1.11.5-eks-6bad6d