finding the apiversion in kubernetes

what is it?

The core of Kubernetes’ control plane is the API server. The API server exposes an HTTP API that lets end users, different parts of your cluster, and external components communicate with one another.

The Kubernetes API lets you query and manipulate the state of API objects in Kubernetes (for example: Pods, Namespaces, ConfigMaps, and Events).

Most operations can be performed through the kubectl command-line interface or other command-line tools, such as kubeadm, which in turn use the API. However, you can also access the API directly using REST calls.

Consider using one of the client libraries if you are writing an application using the Kubernetes API.

https://kubernetes.io/docs/concepts/overview/kubernetes-api/

why?

When you create a kubernetes resource you need to specify the apiVersion of the resource that you want to apply the resource against. With different versions of kubernetes and different CRD’s applied to your cluster keeping track of the version your cluster is setup to use can be a little trickey to remember.

The format of the apiVersion is apiGroup/version unless the resource is part of the core API group in which case youd don’t need to specify the api_group. So to figure out the apiVersion we’ll need to figure out both the api_group and version of a resource.

finding the group

To find get a list of installed api groups you can run the following command:

$ kubectl api-resources

You should get a output that looks similar to the following:

NAME                              SHORTNAMES   APIGROUP                       NAMESPACED   KIND
bindings                                                                      true         Binding
componentstatuses                 cs                                          false        ComponentStatus
configmaps                        cm                                          true         ConfigMap
endpoints                         ep                                          true         Endpoints
events                            ev                                          true         Event
limitranges                       limits                                      true         LimitRange
namespaces                        ns                                          false        Namespace
nodes                             no                                          false        Node
persistentvolumeclaims            pvc                                         true         PersistentVolumeClaim
persistentvolumes                 pv                                          false        PersistentVolume
pods                              po                                          true         Pod
podtemplates                                                                  true         PodTemplate
replicationcontrollers            rc                                          true         ReplicationController
resourcequotas                    quota                                       true         ResourceQuota
secrets                                                                       true         Secret
serviceaccounts                   sa                                          true         ServiceAccount
services                          svc                                         true         Service
challenges                                     acme.cert-manager.io           true         Challenge
orders                                         acme.cert-manager.io           true         Order
mutatingwebhookconfigurations                  admissionregistration.k8s.io   false        MutatingWebhookConfiguration
validatingwebhookconfigurations                admissionregistration.k8s.io   false        ValidatingWebhookConfiguration
customresourcedefinitions         crd,crds     apiextensions.k8s.io           false        CustomResourceDefinition
apiservices                                    apiregistration.k8s.io         false        APIService
controllerrevisions                            apps                           true         ControllerRevision
daemonsets                        ds           apps                           true         DaemonSet
deployments                       deploy       apps                           true         Deployment
replicasets                       rs           apps                           true         ReplicaSet
statefulsets                      sts          apps                           true         StatefulSet
...

If you look in the third column you can see a APIGROUP. For example if we needed to create a new resource for a daemonset we can see the apigroup is apps.

getting the api group version

Using the api group name we can grab the version with

$ kubectl api-versions | grep '^apps/'
apps/v1

As you can see the apps/v1 contains the version required to create a daemonset.