my-docs/kubernetes/workloads/pod.md

Namespace Definition

apiVersion: v1
kind: Namespace
metadata:
  name: my-ns

• apiVersion: Specifies the version of the Kubernetes API.
• kind: Defines the type of Kubernetes object, here it's a Namespace.
• metadata: Contains data that helps uniquely identify the object, including a name.

This YAML file creates a namespace named my-ns which isolates a group of resources within Kubernetes.

Pod Definitions

Nginx Pod

apiVersion: v1
kind: Pod
metadata:
  namespace: my-ns
  name: nginx-pod
  labels:
    app: app1
    zone: staging
    version: v1.0.1
    app.kubernetes.io/product: nginx-pod
spec:
  containers:
    - name: naginx-container
      image: nginx:latest
      ports:
        - containerPort: 80

• metadata.namespace: Specifies the namespace the pod belongs to (my-ns).
• metadata.name: The name of the pod (nginx-pod).
• metadata.labels: Key-value pairs for organizing and selecting resources.
• spec.containers: Specifies the containers within the pod. Each container has:
  • name: Container name.
  • image: The Docker image to run (nginx:latest).
  • ports: List of ports to expose from the container (containerPort: 80).

This file defines a pod named nginx-pod running the latest Nginx container in the my-ns namespace.

Test Pod 1

apiVersion: v1
kind: Pod
metadata:
  namespace: my-ns
  name: testpod1
spec:
  containers:
    - name: c00
      image: ubuntu
      command: ["/bin/bash", "-c", "while true; do echo Hello-Coder; sleep 5 ; done"]
    - name: c01
      image: ubuntu
      command: ["/bin/bash", "-c", "while true; do echo Hello-Programmer; sleep 5 ; done"]

• spec.containers.command: Overrides the default command for the container, in this case, running a looped bash script that prints a message every 5 seconds.

This defines a pod named testpod1 with two Ubuntu containers in the my-ns namespace, each running a different command.

Pod with Resource Requests and Limits

apiVersion: v1
kind: Pod
metadata:
  namespace: my-ns
  name: testpod1
spec:
  containers:
    - name: c00
      image: ubuntu
      command:
        - /bin/bash
        - -c
        - while true; do echo Hello-Coder; sleep 5 ; done
    - name: c01
      image: ubuntu
      command:
        - /bin/bash
        - -c
        - while true; do echo Hello-Programmer; sleep 5 ; done
      resources:
        limits:
          memory: "128Mi"
          cpu: "500m"
        requests:
          memory: "64Mi"
          cpu: "250m"

• resources.limits: Specifies the maximum amount of resources a container can use.
• resources.requests: Specifies the amount of resources a container is guaranteed.

This pod configuration defines resource limits and requests for the containers to ensure they do not exceed specific memory and CPU usage.

Pod with NodeSelector

apiVersion: v1
kind: Pod
metadata:
  namespace: my-ns
  name: testpod3
spec:
  containers:
    - name: c00
      image: ubuntu
      command:
        - /bin/bash
        - -c
        - while true; do echo Hello-Coder; sleep 5 ; done
    - name: c01
      image: ubuntu
      command:
        - /bin/bash
        - -c
        - while true; do echo Hello-Programmer; sleep 5 ; done
      resources:
        limits:
          memory: "128Mi"
          cpu: "500m"
        requests:
          memory: "64Mi"
          cpu: "250m"
  nodeSelector:
    kubernetes.io/hostname: k8s2
    kubernetes.io/disk: ssd

• nodeSelector: Ensures the pod is scheduled on nodes with the specified labels (kubernetes.io/hostname: k8s2 and kubernetes.io/disk: ssd).

This configuration places the pod on specific nodes that match the given labels.

Simple Pod Templates

Basic Pod

apiVersion: v1
kind: Pod
metadata:
  name: myapp
  labels:
    name: myapp
spec:
  containers:
  - name: myapp
    image: <Image>
    resources:
      limits:
        memory: "128Mi"
        cpu: "500m"
    ports:
      - containerPort: <Port>

This is a template for a basic pod named myapp with configurable image and port settings.

Nginx Pod

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  labels:
    app: MyApp
spec:
  containers:
  - name: my-container
    image: nginx:latest
    ports:
    - containerPort: 80

This defines a pod named my-pod running an Nginx container exposing port 80.