Exercise 14.1: Create a Custom Resource Definition

1. CP 노드에 연결된 터미널로 이동

2. 클러스터에 이미 생성된 CRD 확인

   kubectl get crd --all-namespaces

3. CRD 생성

   cat <<EOF | kubectl create -f -
   apiVersion: apiextensions.k8s.io/v1
   kind: CustomResourceDefinition
   metadata:
     # name must match the spec fields below, and be in the form: <plural>.<group>
     name: crontabs.stable.example.com
   spec:
     # group name to use for REST API: /apis/<group>/<version>
     group: stable.example.com
     # list of versions supported by this CustomResourceDefinition
     versions:
       - name: v1
         # Each version can be enabled/disabled by Served flag.
         served: true
         # One and only one version must be marked as the storage version.
         storage: true
         schema:
           openAPIV3Schema:
             type: object
             properties:
               spec:
                 type: object
                 properties:
                   cronSpec:
                     type: string
                   image:
                     type: string
                   replicas:
                     type: integer
     # either Namespaced or Cluster
     scope: Namespaced
     names:
       # plural name to be used in the URL: /apis/<group>/<version>/<plural>
       plural: crontabs
       # singular name to be used as an alias on the CLI and for display
       singular: crontab
       # kind is normally the CamelCased singular type. Your resource manifests use this.
       kind: CronTab
       # shortNames allow shorter string to match your resource on the CLI
       shortNames:
       - ct
   EOF

4. 생성된 CRD 확인

   {
       kubectl get crd crontabs.stable.example.com 
       kubectl describe crd crontabs.stable.example.com
   }

5. 위에서 생성한 CRD의 객체 생성

   cat <<EOF | kubectl create -f -
   apiVersion: "stable.example.com/v1"
       # This is from the group and version of new CRD
   kind: CronTab
       # The kind from the new CRD
   metadata:
     name: new-cron-object
   spec:
     cronSpec: "*/5 * * * *"
     image: some-cron-image
       #Does not exist
   EOF

6. 생성된 CronTab 확인

   {
       kubectl get crontab
       kubectl get ct 
       kubectl describe ct
   }

7. 생성한 CRD 삭제

   kubectl delete crd crontabs.stable.example.com