Merge branch 'main' of https://github.com/anveshmuppeda/kubernetes into feature/microservicesdemo

Author: anveshmuppeda

docs/015-best-practices/001-default-container.md

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+---
+// filepath: docs/015-best-practices/001-default-container.md
+title: "Setting a Default Container in Kubernetes"
+description: "A quick and easy fix to streamline your kubectl commands for multi-container pods."
+sidebar_label: "Default Container"
+sidebar_id: "default-container"
+sidebar_position: 1
+---  
+
+# Setting a Default Container in Kubernetes
+
+**A quick and easy fix to streamline your `kubectl` commands for multi-container pods.**
+
+![Default Container Annotation](./img/default-container.png)
+
+When working with Kubernetes, you've likely encountered pods running multiple containers. This is a common and powerful pattern, often used for sidecars that handle tasks like logging, monitoring, or service mesh proxying. However, this setup can introduce a small but persistent annoyance: `kubectl` commands like `logs` and `exec` require you to specify which container you want to target.
+
+If you forget the `-c` or `--container` flag, `kubectl` simply defaults to the first container defined in the pod's manifest. This might not be the container you're interested in, leading to repeated command corrections and a clunky workflow.
+
+Fortunately, there's a simple and elegant solution to this problem: the `kubectl.kubernetes.io/default-container` annotation.
+
+---
+
+## The Fix: A Simple Annotation
+
+By adding this annotation to your pod's metadata, you can explicitly declare which container should be the default for `kubectl` commands. This eliminates the need to constantly specify the container name, making your interactions with multi-container pods much smoother.
+
+The annotation is a key-value pair:
+
+* **Key:** `kubectl.kubernetes.io/default-container`
+* **Value:** The name of the container you want to set as the default.
+
+You can apply this annotation in a few ways:
+
+* **During Pod Creation:** Include the annotation directly in your pod's YAML manifest.
+* **To an Existing Pod:** Use the `kubectl annotate` command to add or update the annotation on a running pod.
+
+---
+
+## Hands-On Example
+
+Let's walk through a practical example to see how this works.
+
+### 1. The Problem: A Pod with Two Containers
+
+First, let's create a pod with two containers: a main application container and a sidecar container.
+
+Create a file named `multi-container-pod.yaml` with the following content:
+
+```yaml
+apiVersion: v1
+kind: Pod
+metadata:
+  name: my-app
+spec:
+  containers:
+  - name: sidecar-container
+    image: busybox
+    command: ["/bin/sh", "-c", "while true; do echo 'I am a sidecar'; sleep 10; done"]
+  - name: main-container
+    image: nginx
+    ports:
+    - containerPort: 80
+```
+
+Now, create the pod using `kubectl`:
+
+```bash
+kubectl apply -f multi-container-pod.yaml
+```
+
+If you try to get the logs from this pod without specifying a container, `kubectl` will default to the first one listed in the manifest, which is `sidecar-container`:
+
+```bash
+kubectl logs my-app
+```
+
+You'll see the output from the sidecar:
+
+```
+I am a sidecar
+```
+
+To see the logs for the `main-container` (the NGINX container), you would need to explicitly specify it:
+
+```bash
+kubectl logs my-app -c main-container
+```
+
+### 2. The Solution: Applying the Annotation
+
+Now, let's fix this by adding the `kubectl.kubernetes.io/default-container` annotation to our pod. We'll set `main-container` as the default.
+
+#### Option A: Editing the Manifest
+
+You can add the annotation directly to your `multi-container-pod.yaml` file:
+
+```yaml
+apiVersion: v1
+kind: Pod
+metadata:
+  name: my-app
+  annotations:
+    kubectl.kubernetes.io/default-container: "main-container"
+spec:
+  containers:
+  - name: sidecar-container
+    image: busybox
+    command: ["/bin/sh", "-c", "while true; do echo 'I am a sidecar'; sleep 10; done"]
+  - name: main-container
+    image: nginx
+    ports:
+    - containerPort: 80
+```
+
+Then, apply the changes:
+
+```bash
+kubectl apply -f multi-container-pod.yaml
+```
+
+#### Option B: Using `kubectl annotate`
+
+If the pod is already running, you can add the annotation using the `kubectl annotate` command:
+
+```bash
+kubectl annotate pod my-app kubectl.kubernetes.io/default-container="main-container"
+```
+
+### 3. The Result: Simplified Commands
+
+Now that the annotation is in place, try running the `kubectl logs` command again without specifying a container:
+
+```bash
+kubectl logs my-app
+```
+
+This time, you'll see the logs from the `main-container` by default, as you intended. Similarly, if you were to use `kubectl exec`, you would be dropped into the `main-container`.
+
+By taking a moment to add this simple annotation, you can save yourself and your team a lot of time and frustration in the long run. It's a small change that can significantly improve your daily Kubernetes workflow.

docs/015-best-practices/_category_.json

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+{
+  "label": "Kubernetes Best Practices",
+  "position": 15,
+  "link": {
+    "type": "generated-index",
+    "description": "Are you looking to optimize your Kubernetes deployments? This series of guides will help you navigate the complexities of Kubernetes best practices, from resource management to security. Whether you're a beginner or an experienced user, these resources will provide you with the knowledge and tools to enhance your Kubernetes operations and ensure efficient, secure, and scalable applications."
+  }
+}