Enabling Kubernetes PodPresets with kops

Question

I've got a kubernetes cluster which was set up with kops with 1.5, and then upgraded to 1.6.2. I'm trying to use PodPresets. The docs state the following requirements:

1. You have enabled the api type settings.k8s.io/v1alpha1/podpreset
2. You have enabled the admission controller PodPreset
3. You have defined your pod presets

I'm seeing that for 1.6.x, the first is taken care of (how can I verify?). How can I apply the second? I can see that there are three kube-apiserver-* pods running in the cluster (I imagine it's for the 3 azs). I guess I can edit their yaml config from kubernetes dashboard and add PodPreset to the admission-control string. But is there a better way to achieve this?

Answer 1

You can list the API groups which are currently enabled in your cluster either with the api-versions kubectl command, or by sending a GET request to the /apis endpoint of your kube-apiserver:

$ curl localhost:8080/apis
{
  "paths": [
  "/api",
  "/api/v1",
  "...",
  "/apis/settings.k8s.io",
  "/apis/settings.k8s.io/v1alpha1",
  "...",
}

Note: The settings.k8s.io/v1alpha1 API is enabled by default on Kubernetes v1.6 and v1.7 but will be disabled by default in v1.8.

You can use a kops ClusterSpec to customize the configuration of your Kubernetes components during the cluster provisioning, including the API servers.

This is described on the documentation page Using A Manifest to Manage kops Clusters, and the full spec for the KubeAPIServerConfig type is available in the kops GoDoc.

Example:

apiVersion: kops/v1
kind: Cluster
metadata:
  name: k8s.example.com
spec:
  kubeAPIServer:
    AdmissionControl:
      - NamespaceLifecycle
      - LimitRanger
      - PodPreset

To update an existing cluster, perform the following steps:

1. Get the full cluster configuration with

   kops get cluster name --full
   

2. Copy the kubeAPIServer spec block from it.

3. Do not push back the full configuration. Instead, edit the cluster configuration with

   kops edit cluster name
   

4. Paste the kubeAPIServer spec block, add the missing bits, and save.

5. Update the cluster resources with

   kops update cluster nane
   

6. Perform a rolling update to apply the changes:

   kops rolling-update name