Secure With GKE Sandbox

This document describes how to configure Knative serving running on Google Kubernetes Engine (GKE) to use GKE Sandbox for improved workload isolation from the host kernel.


  • Learn how to enable GKE Sandbox on your Knative serving cluster.
  • Deploy a service specified to run on sandboxed nodes.


In this document, you use the following billable components of Google Cloud:

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Before you begin

Add GKE Sandbox node pool to an existing Knative serving Cluster

Follow the steps to add a node pool enabled to use GKE Sandbox to your existing Knative serving cluster. This is where workloads that you opt in to use GKE Sandbox run.

Deploy a workload on the GKE Sandbox node pool

Once you have a GKE cluster with a GKE Sandbox-enabled node pool, update your Knative serving configuration. Also, update each service specification to make use of the new nodes. These updates are required just one time.

Enable the runtime class feature flag

In this section, you enable the Kubernetes runtime class by using Knative feature and extension flags in the config-features ConfigMap in the knative-serving namespace. To enable the runtime class, you set the ConfigMap flag kubernetes.podspec-runtimeclassname to enabled. For more information, see Kubernetes runtime class and Configuring flags in the Knative Features and extensions documentation.

  1. Open the config-features ConfigMap for editing:

    kubectl edit configmap config-features -n knative-serving
  2. Add the kubernetes.podspec-runtimeclassname: enabled feature flag to the data field.

  3. As an alternative to the preceding steps, you can run the following command to patch this flag into your Knative features:

    kubectl patch configmap config-features \
        --type='json' \
        -p="[{'op': 'replace', 'path': '/data/kubernetes.podspec-runtimeclassname', 'value': 'enabled'}]" \
        -n knative-serving
  4. To verify your edits, run the following command to view the ConfigMap:

    kubectl get configmap config-features -n knative-serving -o yaml

    The ConfigMap should resemble the following:

    apiVersion: v1
    kind: ConfigMap
        name: config-features
        namespace: knative-serving
        kubernetes.podspec-runtimeclassname: enabled

Deploy a Service configured to run in GKE Sandbox

After you've enabled the runtime class feature flag, you can create Services that specify a runtimeClassName in the spec. Set the runtimeClassName to gvisor to indicate that a service should run on the GKE Sandbox node pool.

  1. Deploy a "Hello World" Knative application by running the following command:

    cat <<EOF | kubectl apply -f -
    kind: Service
        name: helloworld-go
                runtimeClassName: gvisor
                    -   image:
                        -   name: TARGET
                            value: "gVisor User"

    If the Kubernetes runtime class name feature is enabled, the command should finish without errors.

  2. Get the pods for your service running and their configured runtime class by running:

    kubectl get pods \
        -o=custom-columns=',RUNTIME CLASS:.spec.runtimeClassName,STATUS:.status.phase'

    The output should resemble the following:

    NAME                                              RUNTIME CLASS   STATUS
    helloworld-go-00001-deployment-55f58477f-fxm6m    gvisor          Running

What's next

After verifying that you can deploy untrusted apps on your newly created GKE Sandbox node pool, you're ready to add runtimeClassName: gvisor to the Kubernetes specs for other untrusted services you would like to execute on GKE Sandbox node pools.

Additional reading: