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+---
+layout: post
+title: 'Step 1: K3d Cluster Architecture'
+date: 2025-12-28 03:00:00 -0400
+categories:
+  - blog_app
+highlight: true
+---
+
+[[2025-12-27-intro]]
+
+# 1. K3d Cluster Architecture
+
+In a standard Docker setup, containers share the host's kernel and networking space directly. In Kubernetes, we introduce an abstraction layer: a **Cluster**. For this project, we use **K3d**, which packages **K3s** (a lightweight production-grade K8s distribution) into Docker containers.
+
+```text
+Severed-Infra % tree
+.
+├── README.md
+├── apps
+│   ├── severed-blog-config.yaml
+│   ├── severed-blog-hpa.yaml
+│   ├── severed-blog-service.yaml
+│   ├── severed-blog.yaml
+│   └── severed-ingress.yaml
+├── infra
+│   ├── alloy-env.yaml
+│   ├── alloy-setup.yaml
+│   ├── dashboard
+│   │   ├── dashboard-admin.yaml
+│   │   ├── permanent-token.yaml
+│   │   └── traefik-config.yaml
+│   ├── observer
+│   │   ├── adapter-values.yaml
+│   │   ├── dashboard-json.yaml
+│   │   ├── grafana-ingress.yaml
+│   │   ├── grafana.yaml
+│   │   ├── loki.yaml
+│   │   └── prometheus.yaml
+│   └── storage
+│       └── openebs-sc.yaml
+├── namespaces.yaml
+└── scripts
+    ├── README.md
+    ├── access-hub.sh
+    ├── deploy-all.sh
+    ├── setup-grafana-creds.sh
+    └── tests
+        ├── generated-202-404-blog.sh
+        └── stress-blog.sh
+```
+
+## 1.1 Multi-Node Simulation
+
+- **Server (Control Plane):** The master node. Runs the API server, scheduler, and etcd.
+- **Agents (Workers):** The worker nodes where our application pods run.
+
+### Setting up the environment
+
+We map port `8080` to the internal Traefik LoadBalancer to access services via `*.localhost`.
+
+```bash
+k3d cluster create severed-cluster \
+  --agents 2 \
+  -p "8080:80@loadbalancer" \
+  -p "8443:443@loadbalancer"
+```
+
+## 1.2 Image Registry Lifecycle
+
+Since our `severed-blog` image is local, we side-load it directly into the cluster's internal image store rather than pushing to Docker Hub.
+
+```bash
+docker build -t severed-blog:v0.3 .
+k3d image import severed-blog:v0.3 -c severed-cluster
+```
+
+## 1.3 Namespaces & Storage
+
+We partition the cluster into logical domains. We also install **OpenEBS** to provide dynamic storage provisioning (PersistentVolumes) for our databases.
+
+**`namespaces.yaml`**
+
+```yaml
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: severed-apps
+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: monitoring
+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: kubernetes-dashboard
+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: openebs
+```
+
+**`infra/storage/openebs-sc.yaml`**
+
+```yaml
+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: severed-storage
+provisioner: openebs.io/local
+reclaimPolicy: Delete
+volumeBindingMode: WaitForFirstConsumer
+```
+
+---
+
+## 1.4. Infrastructure Concepts Cheat Sheet
+
+| Object      | Docker Equivalent              | Kubernetes Purpose                                                |
+| ----------- | ------------------------------ | ----------------------------------------------------------------- |
+| Node        | The Host Machine               | A physical or virtual server in the cluster.                      |
+| Pod         | A Container                    | The smallest deployable unit (can contain multiple containers).   |
+| Deployments | `docker-compose up`            | Manages the lifecycle and scaling of Pods.                        |
+| Services    | Network Aliases                | Provides a stable DNS name/IP for a group of Pods.                |
+| HPA         | Auto-Scaling Group             | Automatically scales replicas based on traffic/load.              |
+| Ingress     | Nginx Proxy / Traefik          | Manages external access to Services via HTTP/HTTPS.               |
+| ConfigMap   | `docker run -v config:/etc...` | Decouples configuration files from the container image.           |
+| Secret      | Environment Variables (Secure) | Stores sensitive data (passwords, tokens) encoded in Base64.      |
+| DaemonSet   | `mode: global` (Swarm)         | Ensures one copy of a Pod runs on _every_ Node (logs/monitoring). |
+| StatefulSet | N/A                            | Manages apps requiring stable identities and storage (Databases). |
+
+[[2025-12-27-part-2]]