Kubernetes Automation

Tools and patterns for managing Kubernetes declaratively instead of by hand.

GitOps #

Keep manifests in Git and let a controller in the cluster apply them. Drift is corrected automatically.

TOOL	DESCRIPTION
Argo CD	See Argo CD. UI plus CRDs, syncs apps from Git or Helm
Flux	See Flux CD. Controller toolkit. CLI-first, integrates with Helm and Kustomize

bash
flux bootstrap github --owner=<USER> --repository=<REPO> --path=clusters/prod --personal
flux get all
flux reconcile source git flux-system

Kustomize (built into kubectl) #

COMMAND	DESCRIPTION
`kubectl kustomize <DIR>`	Render a kustomization
`kubectl apply -k <DIR>`	Apply a kustomization
`kubectl diff -k <DIR>`	Preview changes

kustomization.yaml

yaml
resources:
  - deployment.yaml
  - service.yaml
namespace: prod
images:
  - name: nginx
    newTag: "1.27"
patches:
  - path: replicas-patch.yaml

Helm #

See Helm Cheat-Sheet. Use helm upgrade --install --atomic in pipelines.

Validating Manifests Before Applying #

COMMAND	DESCRIPTION
`kubectl apply --dry-run=client -f <FILE>`	Local validation
`kubectl apply --dry-run=server -f <FILE>`	Validation by the API server
`kubectl diff -f <FILE>`	Show what would change
`kubeconform -strict -summary <DIR>`	Validate against the Kubernetes schemas
`kube-linter lint <DIR>`	Best-practice lint
`datree test <FILE>`	Policy check, see Datree

Autoscaling #

COMMAND	DESCRIPTION
`kubectl autoscale deployment <NAME> --min=2 --max=10 --cpu-percent=70`	Create a Horizontal Pod Autoscaler
`kubectl get hpa`	List autoscalers
`kubectl top pods` / `kubectl top nodes`	Live usage (needs metrics-server)

Scheduled and Batch Work #

COMMAND	DESCRIPTION
`kubectl create cronjob <NAME> --image=<IMAGE> --schedule="0 3 * * *" -- <CMD>`	Create a CronJob
`kubectl create job <NAME> --from=cronjob/<CRON>`	Run a CronJob now
`kubectl get jobs,cronjobs`	List them

Rollouts #

COMMAND	DESCRIPTION
`kubectl rollout status deployment/<NAME>`	Wait for a rollout (good CI gate)
`kubectl rollout restart deployment/<NAME>`	Rolling restart
`kubectl rollout history deployment/<NAME>`	Revision history
`kubectl rollout undo deployment/<NAME> --to-revision=<N>`	Roll back

Dependency Updates #

Renovate can open PRs to bump image tags, Helm charts and Argo CD/Flux manifests automatically. Enable the kubernetes, helm-values, argocd and flux managers in renovate.json.