Setting Runtime Classes

Create a kata-runtime runtime class to run Kata Containers in a Kubernetes cluster.

CRI-O uses the Kubernetes RuntimeClass resource in the pod configuration file to specify whether to run a pod using the default runtime runc, or using kata-runtime.

The examples in this book use the name native to specify the use of runc, and the name kata-containers to specify the use of the Kata Containers runtime, but the names aren't important.

1. Create a runtime class file for Kata Containers.

   Create a file for a runtime class for Kata Containers named kata-runtime.yaml with the following contents:

   kind: RuntimeClass
   apiVersion: node.k8s.io/v1
   metadata:
       name: kata-containers
   handler: kata

2. Load the runtime class file.

   Load the runtime class to the Kubernetes deployment:

   kubectl apply -f kata-runtime.yaml

   The runtime class kata-containers can now be used in pod configuration files to specify that a container is to be run as a Kata Container, using the kata-containers runtime. For examples of creating pods using this runtime class, see Creating Kata Containers.

3. (Optional) Create a runtime class file for runc.

   Use the same approach to specify a runtime for runc. This is an optional configuration step. As runc is the default runtime, pods automatically run using runc unless you specify otherwise. This file is named runc-runtime.yaml:

   kind: RuntimeClass
   apiVersion: node.k8s.io/v1
   metadata:
       name: native
   handler: runc 

4. (Optional) Load the runtime class file.

   Load the runtime class to the Kubernetes deployment:

   kubectl apply -f runc-runtime.yaml

   The runtime class native can be used in pod configuration files to specify that a container runs as a runC container, using the runc runtime.

5. List the runtime classes.

   You can see a list of the available runtime classes for a Kubernetes cluster using the kubectl get runtimeclass command:

   kubectl get runtimeclass

   The output looks similar to:

   NAME              HANDLER   AGE
   kata-containers   kata      7m29s
   native            runc      7m7s