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Summary - CRD

Combine YAML and validation to write a CRD.

Summary: CRD

In this group:

  • A CRD adds a new type to the API; objects are stored in etcd and managed with kubectl and RBAC.
  • The name is plural.group; names, scope, versions (served/storage) and openAPIV3Schema.
  • Custom resource: apiVersion: group/version, kind; additionalPrinterColumns enrich the table.
  • subresources.status keeps the spec/status split; scale gives kubectl scale and HPA support.
  • Validation definitions (required, min/max, enum, pattern, default) and CEL rules reject broken data up front.
kubectl apply -f crd.yaml
kubectl apply -f yedek.yaml
kubectl get yd -A

Practice Printer columns

Write a CRD version's additionalPrinterColumns section (starting with additionalPrinterColumns:): Veritabani (type: string, jsonPath: .spec.veritabani) and Durum (type: string, jsonPath: .status.durum).

Starter code

terminal
# buraya yaz

Sample solution

terminal
additionalPrinterColumns:
  - name: Veritabani
    type: string
    jsonPath: .spec.veritabani
  - name: Durum
    type: string
    jsonPath: .status.durum

Expected output

customresourcedefinition.apiextensions.k8s.io/yedekler.ornek.com configured
$ kubectl get yd -n magaza
NAME          VERITABANI   DURUM      AGE
magaza-gece   db           Basarili   1d

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is needed for a custom resource to gain behaviour?

  • A more detailed validation definition
  • A ClusterRole
  • An additional printer column
  • A controller (operator) watching and reconciling it Correct answer

Explanation: In the next group you'll write an operator.

2 Give the field a default value.

Question 
saklamaGun: {type: integer, minimum: 1, ____: 7}
Answer 
saklamaGun: {type: integer, minimum: 1, default: 7}

Explanation: default is applied if the field isn't written.

3 Match.

Term Meaning
CRD Type
CR Object
openAPIV3 definition Validation
status Controller report

All lessons in Expert

1 Kubernetes internals

  1. What is etcd?
  2. kube-scheduler
  3. controller-manager
  4. kube-apiserver
  5. Reconcile loop
  6. Summary - Internals

2 Custom Resource Definition

  1. What is a CRD?
  2. CRD YAML
  3. Custom resource
  4. Spec and status
  5. Validation
  6. Summary - CRD

3 Operator pattern

  1. What is an Operator?
  2. Controller logic
  3. Operator SDK
  4. Custom resource management
  5. Example operator
  6. Summary - Operator

4 Service mesh - Istio

  1. What is a service mesh?
  2. What is Istio?
  3. Envoy sidecar
  4. Traffic management
  5. mTLS
  6. Summary - Service mesh

5 Multi-cluster

  1. What is multi-cluster?
  2. Cluster federation
  3. Kubeconfig
  4. Cross-cluster service
  5. Cluster registry
  6. Summary - Multi-cluster

6 OPA and Gatekeeper

  1. What is OPA?
  2. The Rego language
  3. What is Gatekeeper?
  4. ConstraintTemplate
  5. Constraint
  6. Summary - OPA

7 Disaster recovery

  1. Backup strategy
  2. etcd backup
  3. Velero
  4. Restore process
  5. RPO and RTO
  6. Summary - Disaster recovery

8 Expert final

  1. Challenge - CRD
  2. Challenge - Operator
  3. Challenge - Istio
  4. Challenge - OPA
  5. Challenge - Expert project