Export yaml definition of k8s deployment

export_yaml_definition_k8s_deyploment.md

Export yaml definition of k8s deployment

The motiviation for this gist was the deprecation of the --export flag. Having the yaml definition of a running deployment has the advantage that it can be saved and edited. For example when updating the version of an image.

Obtaining the current definition

For this example we will just use a deployment of the Kubernetes Deployment documentation. This can be deployed using the command

kubectl apply -f https://k8s.io/examples/controllers/nginx-deployment.yaml

To get the yaml definition the get command can be used:

kubectl get -o=yaml deployments.apps nginx-deployment > /tmp/export.yml

Since the aim of this example is to edit and rollout the changes the output is redirect to a file > /tmp/export.yml

Removing superfluous parts

The saved definition contains some information that is not needed:

metadata:
  annotations:
    deployment.kubernetes.io/revision: "4"
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"labels":{"app":"nginx"},"name":"nginx-deployment","namespace":"default"},"spec":{"progressDeadlineSeconds":600,"replicas":3,"revisionHistoryLimit":10,"selector":{"matchLabels":{"app":"nginx"}},"strategy":{"rollingUpdate":{"maxSurge":"25%","maxUnavailable":"25%"},"type":"RollingUpdate"},"template":{"metadata":{"creationTimestamp":null,"labels":{"app":"nginx"}},"spec":{"containers":[{"image":"nginx:1.8.1","imagePullPolicy":"IfNotPresent","name":"nginx","ports":[{"containerPort":80,"protocol":"TCP"}],"resources":{},"terminationMessagePath":"/dev/termination-log","terminationMessagePolicy":"File"}],"dnsPolicy":"ClusterFirst","restartPolicy":"Always","schedulerName":"default-scheduler","securityContext":{},"terminationGracePeriodSeconds":30}}}}
  creationTimestamp: "2019-12-23T13:16:24Z"
  generation: 4
  labels:
    app: nginx
  name: nginx-deployment
  namespace: default
  resourceVersion: "2193"
  selfLink: /apis/apps/v1/namespaces/default/deployments/nginx-deployment
  uid: 1c7f7359-4f28-4116-b5a1-a10ebe218f0c
...
status:
  availableReplicas: 3
  conditions:
  - lastTransitionTime: "2019-12-23T13:16:54Z"
    lastUpdateTime: "2019-12-23T13:16:54Z"
    message: Deployment has minimum availability.
    reason: MinimumReplicasAvailable

Actually most of the metadata can be deleted expect name, namespace, your own lables and annotations. The status part is not needed at all. After the removal of these parts the deployment can be edited and updated using Declarative deployment