Add detailed articles on Kubernetes components including CoreDNS, CSI…

… Driver, etcd, Kube-API Server, Kube Controller Manager, Kube-Proxy, Kube-Scheduler, kubectl, and Kubelet. Each article provides an in-depth understanding of their roles, architectures, configurations, and best practices for management and troubleshooting in a Kubernetes environment.

blog/content/training/kubernetes-deep-dive/cluster-dns-coredns.md

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+---
+title: "Understanding Cluster DNS with CoreDNS in Kubernetes"
+date: 2025-01-29T00:00:00-00:00
+draft: false
+tags: ["kubernetes", "coredns", "cluster dns", "networking"]
+categories: ["Kubernetes Deep Dive"]
+author: "Matthew Mattox"
+description: "A deep dive into CoreDNS, Kubernetes' default Cluster DNS service, its architecture, configuration, and troubleshooting."
+url: "/training/kubernetes-deep-dive/cluster-dns-coredns/"
+---
+
+## Introduction
+
+In a Kubernetes cluster, DNS plays a crucial role in **service discovery and inter-pod communication**. Kubernetes uses **CoreDNS** as the default DNS server to resolve internal and external domain names efficiently.
+
+In this deep dive, we'll cover:
+- What CoreDNS is and why it's important
+- How CoreDNS integrates with Kubernetes
+- CoreDNS configuration and customization
+- Common troubleshooting steps
+
+---
+
+## What is CoreDNS?
+
+**CoreDNS** is a flexible, extensible, and high-performance **DNS server** designed specifically for **Kubernetes environments**. It serves as the **Cluster DNS**, resolving internal Kubernetes services and external domains.
+
+### **Why CoreDNS?**
+- **Scalable & Lightweight** – Designed for high-performance DNS resolution.
+- **Pluggable Architecture** – Allows custom DNS functionalities through plugins.
+- **Secure** – Supports DNSSEC, caching, and request filtering.
+- **Cloud-Native** – Runs as a **Kubernetes-native** service.
+
+CoreDNS was introduced in Kubernetes **v1.11**, replacing **kube-dns** as the default DNS service.
+
+---
+
+## How CoreDNS Works in Kubernetes
+
+CoreDNS runs as a **Deployment** in the `kube-system` namespace and operates as a **DNS Service** (`kube-dns`). It listens on port `53` (UDP and TCP) and resolves **internal Kubernetes services**.
+
+### **CoreDNS Workflow**
+1. **A pod makes a DNS request** (e.g., `curl http://my-service.default.svc.cluster.local`).
+2. **CoreDNS checks its local cache** for an existing record.
+3. **If not cached, CoreDNS queries the Kubernetes API** to resolve the requested service.
+4. **The IP of the service is returned** to the pod.
+5. **If the request is for an external domain**, CoreDNS forwards it to an upstream resolver (e.g., Google DNS, Cloudflare).
+
+---
+
+## CoreDNS Configuration in Kubernetes
+
+The CoreDNS configuration is stored in a **ConfigMap** in the `kube-system` namespace:
+
+### **View CoreDNS ConfigMap**
+```bash
+kubectl get configmap coredns -n kube-system -o yaml
+```
+
+### **Default CoreDNS Configuration**
+```yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: coredns
+  namespace: kube-system
+data:
+  Corefile: |
+    .:53 {
+        errors
+        health
+        ready
+        kubernetes cluster.local in-addr.arpa ip6.arpa {
+            pods insecure
+            fallthrough in-addr.arpa ip6.arpa
+        }
+        forward . /etc/resolv.conf
+        cache 30
+        loop
+        reload
+        loadbalance
+    }
+```
+
+### **Key Directives in the Corefile**
+- **`kubernetes cluster.local`** – Handles internal service resolution.
+- **`forward . /etc/resolv.conf`** – Forwards external queries to upstream DNS.
+- **`cache 30`** – Caches DNS responses for 30 seconds.
+- **`health` & `ready`** – Provide health checks for CoreDNS pods.
+- **`reload`** – Enables dynamic reloading of configuration.
+
+---
+
+## Customizing CoreDNS
+
+### **1. Changing Upstream DNS Servers**
+Modify the `forward` directive to use custom resolvers (e.g., Google DNS, Cloudflare):
+```yaml
+forward . 8.8.8.8 8.8.4.4
+```
+Apply the changes:
+```bash
+kubectl apply -f coredns-config.yaml -n kube-system
+kubectl rollout restart deployment coredns -n kube-system
+```
+
+### **2. Adding Custom Domain Resolutions**
+To manually define **static DNS entries**, use the `hosts` plugin:
+```yaml
+hosts {
+    192.168.1.100 custom-app.local
+    fallthrough
+}
+```
+
+### **3. Enabling Log Output for Debugging**
+To log DNS queries:
+```yaml
+log
+errors
+```
+Apply the changes and check logs:
+```bash
+kubectl logs -n kube-system deployment/coredns
+```
+
+---
+
+## Troubleshooting CoreDNS Issues
+
+### **1. Check CoreDNS Pods**
+```bash
+kubectl get pods -n kube-system -l k8s-app=kube-dns
+```
+
+### **2. Check DNS Resolution Inside a Pod**
+```bash
+kubectl run -it --rm --restart=Never --image=busybox dns-test -- nslookup my-service.default.svc.cluster.local
+```
+
+### **3. Restart CoreDNS Deployment**
+```bash
+kubectl rollout restart deployment coredns -n kube-system
+```
+
+### **4. Verify DNS ConfigMap**
+```bash
+kubectl describe configmap coredns -n kube-system
+```
+
+### **5. Test External DNS Resolution**
+```bash
+kubectl run -it --rm --restart=Never --image=busybox dns-test -- nslookup google.com
+```
+
+---
+
+## Best Practices for CoreDNS Management
+
+1. **Monitor CoreDNS Logs & Metrics**  
+   - Use **Prometheus** & **Grafana** to track DNS performance.
+
+2. **Optimize DNS Cache TTL**  
+   - Adjust the `cache` setting based on workload requirements.
+
+3. **Load Balance DNS Queries**  
+   - Enable `loadbalance` to distribute DNS traffic evenly.
+
+4. **Use Multiple DNS Pods for High Availability**  
+   - Increase replicas for better resilience:
+   ```bash
+   kubectl scale deployment coredns --replicas=3 -n kube-system
+   ```
+
+5. **Secure External DNS Requests**  
+   - Restrict outgoing DNS queries to prevent DNS leaks.
+
+---
+
+## Conclusion
+
+CoreDNS is a **critical component** of Kubernetes networking, ensuring **service discovery and efficient DNS resolution**. By understanding how it works, configuring it properly, and troubleshooting effectively, you can maintain a **reliable and scalable** Kubernetes cluster.
+
+For more Kubernetes deep dives, visit [support.tools](https://support.tools)!

blog/content/training/kubernetes-deep-dive/csi-driver.md

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+---
+title: "Understanding CSI (Container Storage Interface) Driver in Kubernetes"
+date: 2025-01-29T00:00:00-00:00
+draft: false
+tags: ["kubernetes", "csi", "storage", "persistent volumes"]
+categories: ["Kubernetes Deep Dive"]
+author: "Matthew Mattox"
+description: "A deep dive into the Container Storage Interface (CSI) in Kubernetes, how it works, and why it's essential for modern cloud-native storage management."
+url: "/training/kubernetes-deep-dive/csi-driver/"
+---
+
+## Introduction
+
+Storage in Kubernetes has evolved significantly, and one of the most critical advancements is the **Container Storage Interface (CSI)**. CSI allows Kubernetes to integrate **third-party storage solutions** in a standardized and flexible manner.
+
+In this deep dive, we'll explore:
+- What CSI is and why it's important
+- The architecture and components of a CSI driver
+- How CSI interacts with Kubernetes
+- How to deploy and use a CSI driver
+
+## What is the Container Storage Interface (CSI)?
+
+CSI is an **open standard API** that enables Kubernetes to work with various storage backends. Instead of relying on in-tree storage plugins, CSI allows **storage providers** to develop their own drivers **independent of Kubernetes releases**.
+
+### Why CSI?
+- **Decouples Storage from Kubernetes Core** – No need to modify Kubernetes for new storage integrations.
+- **Supports Dynamic Storage Provisioning** – Automates volume creation based on demand.
+- **Works Across Platforms** – Compatible with different cloud providers and on-prem solutions.
+- **Simplifies Maintenance & Upgrades** – Storage vendors can update their CSI drivers without waiting for Kubernetes updates.
+
+---
+
+## CSI Driver Architecture
+
+A **CSI driver** consists of several components that enable Kubernetes to communicate with external storage systems.
+
+### **Key Components of a CSI Driver**
+1. **Controller Plugin**  
+   - Runs as a Deployment in Kubernetes.  
+   - Handles volume lifecycle management (create, delete, attach, detach).  
+   - Talks to the external storage API (e.g., AWS EBS, Ceph, vSphere, etc.).
+
+2. **Node Plugin**  
+   - Runs as a DaemonSet on each node.  
+   - Mounts volumes to pods when requested.  
+   - Communicates with the container runtime (`containerd` or `CRI-O`).
+
+3. **CSI Sidecars**  
+   - Kubernetes provides helper containers to facilitate CSI functionality:  
+     - **csi-provisioner**: Manages volume provisioning.  
+     - **csi-attacher**: Handles volume attachment/detachment.  
+     - **csi-resizer**: Allows volume expansion.  
+     - **csi-snapshotter**: Manages volume snapshots.  
+     - **csi-node-driver-registrar**: Registers the CSI driver with kubelet.
+
+### **How Kubernetes Interacts with CSI**
+1. **A Pod Requests a Volume**  
+   - Kubernetes checks if a Persistent Volume (PV) exists or needs to be created.
+
+2. **CSI Controller Plugin Handles Volume Creation**  
+   - If dynamic provisioning is enabled, CSI creates a new volume via the storage provider API.
+
+3. **Volume Gets Attached to the Node**  
+   - The **CSI Node Plugin** ensures the volume is mounted correctly.
+
+4. **The Pod Uses the Volume**  
+   - Kubernetes schedules the pod and provides access to the mounted storage.
+
+5. **Volume Gets Released When the Pod is Deleted**  
+   - CSI ensures the volume is detached and can be reused or deleted.
+
+---
+
+## Deploying a CSI Driver in Kubernetes
+
+### Step 1: Install the CSI Driver  
+Different cloud providers offer their own CSI drivers. Here are some popular ones:
+- **AWS EBS CSI Driver**:  
+  ```bash
+  helm repo add aws-ebs-csi-driver https://kubernetes-sigs.github.io/aws-ebs-csi-driver
+  helm install aws-ebs aws-ebs-csi-driver/aws-ebs-csi-driver --namespace kube-system
+  ```
+
+- **Google Cloud PD CSI Driver**:  
+  ```bash
+  kubectl apply -k "github.com/kubernetes-sigs/gcp-compute-persistent-disk-csi-driver/deploy/kubernetes/overlays/stable"
+  ```
+
+- **Azure Disk CSI Driver**:  
+  ```bash
+  helm repo add azuredisk-csi-driver https://raw.githubusercontent.com/kubernetes-sigs/azuredisk-csi-driver/master/charts
+  helm install azuredisk-csi-driver azuredisk-csi-driver/azuredisk-csi-driver --namespace kube-system
+  ```
+
+### Step 2: Create a StorageClass  
+```yaml
+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: csi-storage
+provisioner: ebs.csi.aws.com  # Replace with the appropriate CSI driver name
+parameters:
+  type: gp3
+```
+
+### Step 3: Create a Persistent Volume Claim (PVC)  
+```yaml
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: my-pvc
+spec:
+  accessModes:
+    - ReadWriteOnce
+  storageClassName: csi-storage
+  resources:
+    requests:
+      storage: 10Gi
+```
+
+### Step 4: Attach the PVC to a Pod  
+```yaml
+apiVersion: v1
+kind: Pod
+metadata:
+  name: csi-pod
+spec:
+  containers:
+    - name: my-container
+      image: busybox
+      volumeMounts:
+        - mountPath: "/data"
+          name: storage
+  volumes:
+    - name: storage
+      persistentVolumeClaim:
+        claimName: my-pvc
+```
+
+---
+
+## Troubleshooting CSI Issues
+
+| Issue | Cause | Solution |
+|-------|------|----------|
+| PVC stuck in `Pending` state | CSI driver not installed or misconfigured | Check `kubectl get pods -n kube-system` for errors |
+| Volume not attaching to the node | Node plugin not running or insufficient permissions | Ensure `csi-node` DaemonSet is running |
+| Storage class not recognized | Incorrect provisioner name | Verify `kubectl get storageclass` output |
+| Snapshot restore failure | CSI Snapshotter not installed | Deploy `csi-snapshotter` sidecar |
+
+---
+
+## Best Practices for Using CSI in Kubernetes
+
+1. **Use the latest CSI driver versions**  
+   - Regular updates improve performance, security, and feature support.
+
+2. **Monitor Storage Usage**  
+   - Use Prometheus and Grafana to track storage consumption.
+
+3. **Implement Volume Snapshots & Backups**  
+   - Set up CSI snapshots to protect against data loss.
+
+4. **Tune Performance Parameters**  
+   - Optimize volume performance based on workload needs.
+
+5. **Test in a Staging Environment First**  
+   - Avoid production disruptions by testing new storage configurations in a non-production cluster.
+
+---
+
+## Conclusion
+
+The **Container Storage Interface (CSI)** has **revolutionized Kubernetes storage management**, enabling seamless integration with cloud and on-prem storage solutions. By understanding CSI drivers, how they interact with Kubernetes, and best practices for deployment, you can **efficiently manage persistent storage in your cluster**.
+
+For more Kubernetes deep dive topics, visit [support.tools](https://support.tools)!