DevOps Classroom notes 26/Dec/2025

Pods

• Pods contain containers in it
• Pods have 3 types of containers
  • containers: These contain application containers and they execute in parallel. This is mandatory
  • init containers: These containers will start first and once they finish executing the containers will start. Containers here will start in sequence.
    • We will have containers which act as pre-condition
    • optional contianer
  • ephemeral containers: for debugging purposes (optional)

Example 1: I want a httpd container inside a pod

• Refer Here for api reference
• metadata: In metadata as of now we will add two details
  • name
  • labels: labels in k8s are key value apirs, which can be used to query
• Manifest

---
apiVersion: v1
kind: Pod
metadata:
  name: example-1
  labels:
    app: httpd
    purpose: learning
    env: dev
spec:
  containers:
    - name: httpd
      image: httpd:latest
      ports:
        - name: httpd
          protocol: TCP
          containerPort: 80

• killercoda

Pods contd

• Each Pod gets a unique ip address
• Each Pod has a lifecycle
  

Example 2: Pod with container with stops

• Manifest

---
apiVersion: v1
kind: Pod
metadata:
  name: example-2
  labels:
    app: hello-world
    env: dev
    topic: "exiting-containers"
spec:
  containers:
    - name: suicidal
      image: hello-world:latest

Example 3: Pod with two containers

• Lets create a pod with two containers
  • first container will be nginx
  • second container will be tomcat

---
apiVersion: v1
kind: Pod
metadata:
  name: example-3
  labels:
    app: web
    purpose: multi-container
spec: 
  - name: nginx
    image: nginx:latest
    ports:
      - containerPort: 80
  - name: tomcat
    image: tomcat:latest
    ports:
      - containerPort: 8080

Example 4: lets use init containers with sleep 3s and 4s and nginx

• manifest

---
apiVersion: v1
kind: Pod
metadata:
  name: example-4
  labels:
    purpose: init-container-demo
    app: nginx
spec:
  initContainers:
    - name: init-0
      image: alpine
      command: 
        - sleep
        - "3s"
    - name: init-1
      image: alpine
      command:
        - sleep
        - "4s"
  containers:
    - name: nginx
      image: nginx:latest
      ports:
        - containerPort: 80

Prompts

1. Understanding manifest w.r.t apiServer/cluster

You are kubernetes api-server. I will give you k8s manifest 
tell me what you will be doing and give me in plain english what the manifest is all about.

1. Understanding manifest and knowing best practices

you are kubernetes expert, I will give you manifest files, explain what it does and also suggest me best practices around this manifest