Cloud Desktop Teaching Platforms

This course session provides a hands-on, practical deep dive into Kubernetes resource management, focusing on the creation, scaling, and deletion of Deployments, StatefulSets, and DaemonSets. The instructor emphasizes YAML syntax accuracy as a primary source of troubleshooting errors, walks through real-time cluster operations using kubectl, and highlights key behavioral differences between resource types—particularly the requirement to scale StatefulSets to zero before deletion. The session concludes with a review of core concepts including namespace isolation, label-based resource querying, and cluster-wide application deployment via DaemonSets.

Topic (Timeline)

1. Introduction and YAML Syntax Emphasis [00:00:00 - 00:01:04]

Instructor begins by noting pending participants and recapping the prior lesson: namespace creation and pod manifest deployment.
Highlights that ~50% of Kubernetes troubleshooting stems from YAML syntax errors.
Stresses the importance of learning to read and debug manifests—even those created by others (e.g., Helm values.yaml)—to identify structural issues.

2. Deployment and ReplicaSet Management [00:01:04 - 00:05:00]

Guides students through creating a Deployment using a YAML manifest on a fresh Minikube cluster.
Demonstrates kubectl get deployments, kubectl get replicasets, and kubectl describe to inspect resource relationships.
Explains that Deployments automatically create ReplicaSets with unique hash suffixes, and each Pod inherits a unique hash from its ReplicaSet.
Shows scaling a Deployment from 3 to 4 replicas using kubectl scale deployment <name> --replicas=4 without modifying the YAML file.
Verifies changes via describe and observes new Pod hash generation.
Scales back to 3 replicas and confirms deletion of the most recently created Pod.
Deletes the Deployment, which automatically removes its associated ReplicaSet and Pods.

3. StatefulSet Creation and Behavior [00:05:00 - 00:15:50]

Instructs students to create a StatefulSet by modifying the prior Deployment YAML file (e.g., nginx-stapleset.yaml).
Clarifies that ReplicaSet controllers are deprecated; Deployments now manage ReplicaSets.
Highlights key differences: StatefulSets assign stable, sequential names (e.g., nginx-stapleset-0, nginx-stapleset-1) without hash suffixes.
Demonstrates applying the StatefulSet, correcting a common error (incorrect replica count: 3 → 2).
Uses kubectl get pods -l app=nginx to query resources by label.
Explains label usage: labels enable targeted resource discovery; missing labels cause resources to be excluded from queries.
Scales StatefulSet from 2 to 1 pod: confirms deletion of the highest-indexed pod (-1), leaving -0 (always deletes backward).
Scales from 1 to 10 pods: observes sequential creation (-0 to -9) and confirms no deletion events for existing pods.
Emphasizes critical behavior: StatefulSets must be scaled to zero replicas before deletion—otherwise, deletion may fail silently.
Warns that Helm charts often fail to delete StatefulSets properly because they do not auto-scale to zero, leaving running pods.

4. DaemonSet Deployment and Cluster-Wide Behavior [00:15:50 - 00:20:40]

Sets up a 3-node Minikube cluster (minikube start --nodes=3) to demonstrate cluster-wide deployment.
Confirms presence of CNI (kindnet) and kube-proxy on all nodes.
Deploys Fluentd as a DaemonSet to illustrate one-pod-per-node behavior.
Observes that DaemonSet Pods may have different creation times due to image pull delays across nodes.
Shows kubectl get daemonsets and kubectl get pods -o wide to verify pod distribution.
Deletes the DaemonSet using kubectl delete daemonset fluentd (unlike StatefulSets, no scale-to-zero required).
Notes that DaemonSets are ideal for cluster-level services (logging, monitoring, networking).

5. Review and Lesson Wrap-up [00:20:40 - 00:22:40]

Summarizes key learnings:
- Namespace isolation and resource cleanup via namespace deletion.
- Label-based resource querying (kubectl get all -l app=...).
- Deployments manage ReplicaSets; scaling and deletion are automatic.
- StatefulSets use stable, ordered names and require scale-to-zero before deletion.
- DaemonSets ensure one Pod per node for cluster-wide services.
Announces upcoming break and transition to Lesson 5.

Appendix

Key Principles

YAML Syntax: Critical to success; errors are common and often non-descriptive. Always validate structure, indentation, and field names.
Label Queries: Use -l key=value to filter resources across namespaces. Missing labels = invisible in queries.
StatefulSet Deletion: Must scale replicas to 0 before kubectl delete. Helm charts may not handle this, leading to orphaned pods.
DaemonSet Behavior: Automatically schedules one Pod per node; ideal for infrastructure services (logging, monitoring, CNI).

Tools Used

minikube start --nodes=3 — Multi-node cluster setup
kubectl get deployments,replicasets,statefulsets,daemonsets,pods
kubectl describe <resource> <name>
kubectl scale deployment/statefulset <name> --replicas=N
kubectl delete -f <file> — For declarative deletion
kubectl delete daemonset <name> — Direct deletion supported
kubectl get pods -l app=<label> — Label-based filtering

Common Pitfalls

Incorrect YAML indentation (e.g., spec: vs spec: with wrong spacing).
Forgetting to delete StatefulSet pods before deleting the StatefulSet itself.
Assuming kubectl delete -f works the same for all resource types (it does not for StatefulSets).
Misunderstanding label scope: labels are per-resource, not global; cross-namespace queries require -A.
Assuming DaemonSet Pods deploy instantly; image pulls cause staggered creation times.

Practice Suggestions

Recreate all four resource types (Deployment, ReplicaSet, StatefulSet, DaemonSet) from scratch without reference.
Intentionally break YAML syntax and interpret the error output.
Label a mix of resources and query them with kubectl get all -l <label>.
Test StatefulSet deletion without scaling to zero—observe the behavior.
Deploy a DaemonSet on a 2-node cluster and verify one Pod per node.

Kubernetes - Basic to Advanced - lane-qaca-20260107-000045

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Summary

Overview