Kubernetes Deployment Strategies Guide 🚀
Recreate and Rolling Update Deployments in Kubernetes
Recreate Strategy 🔄
- Old containers are all deleted first.
- New containers get up after the previous ones are deleted.
- Will face downtime.
Rolling Update Strategy (Default) 🔄
- One by one, an old container is deleted and a new one is created at the same time.
- Ensures zero downtime.
Deployment and Rollback Commands
To deploy:
kubectl apply -f deployment.yamlTo rollback:
kubectl rollout undo deployment/<deployment-name>To view the history of deployments:
kubectl rollout history deployment/<deployment-name>CMD & Entrypoint / Command & Args
Environment Variables / Config Maps / Secrets
Config Maps 🌐
Used to store environment variables using a definition file.
- To get or describe a ConfigMap:
kubectl get configmap/cm
kubectl describe configmap/cm- To attach a ConfigMap to a pod (using its name):
envFrom:
- configMapRef:
name: <config-map-name>Secrets 🔒
Used to store sensitive information (user/password).
- In Secrets, variables can be stored in an encoded format.
To encode secrets data in base64:
echo -n 'my-secret-data' | base64- To get or describe a Secret:
kubectl get secrets
kubectl describe secrets my-secret
kubectl get secrets -o yamlTo decode base64 encoded values for a secret:
echo 'encoded-secret' | base64 --decode- To attach Secrets to a pod YAML file (using its name):
envFrom:
- secretRef:
name: <secret-name>Other Ways to Handle Secrets
- Secret Manager in AWS/Azure/GCP or any vault (encrypted).
- Helm Secrets and HashiCorp Vault for handling sensitive data.
ETCD Encryption (Data at Rest) 🔐
Multi-Container Pods 🐙
Init Containers ⏳
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When a pod is first created, the init container runs.
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The process in the init container must complete before the main container starts.
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Multiple init containers can be configured to run sequentially.
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If an init container fails, Kubernetes restarts the pod repeatedly until the init container succeeds.
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Note: Init containers don't show in the output of
kubectl get pods.
To get logs of an init container:
kubectl logs <podname> -c <initContainer-name>Liveness and Readiness Probes
- Liveness and readiness probes are not required for the CKA exam, but are crucial for production environments.