DevOps Classroom notes 06/Oct/2026

Pod:

• pod is smallest deployment unit in k8s

ALL container in pods

• we have same network ip address
• having shared volume
• Are started and stoped as a unit.

Types of container

1. containers:

• this is used for application container
• all container will run parellel
• Mandatory atlest one container

2. init-container:

• pre-conditional run before container start
• this will be run in sequence
• Optional
• this container will run and complete state.

alpine ==> bash ==> curl download dependancy ==> create folder and add files 

3. ephemeralContainers:

• temporary container for debug
• Optional

kubectl debug -it <pod> --image=<image> --target=<container>

API Referance link

apiVersion: v1
kind: Pod
metadata:
  name: sample-pod
  labels:
    app: sample
    environment: production
spec:
  containers:
    - name: sample-container
      image: nginx:latest
      ports:
        - containerPort: 80
  initContainers:
    - name: init-sample
      image: busybox:latest
      command: ["sh", "-c", "echo Initializing... && sleep 5"]

killercoda for k8s playground

Pod lifecycle:

Offical doc for pod lifecycle

1. pending: accept the cluster to create pod, also will pull images for container and init container
2. Running: bound to node and at least one container will started running
3. succeeded: all init container or container run and exist with status code o
4. Failed: if any container is failled and terminated
5. Unknow: pod state can’t be determined.(resource issue, node problems , network issues)

Container states:

1. waiting: (not yet running container but its in pulling images and runing init container)
2. Running: Executing normally (application is runing)
3. terminated: Finshed or failed

note deploy below yaml and test the container state by describe pod

apiVersion: v1
kind: Pod
metadata:
  name: sample-pod
  labels:
    app: sample
    environment: production
spec:
  containers:
    - name: sample-container
      image: nginx:latest
      ports:
        - containerPort: 80
    - name: init-sample
      image: busybox:latest
      command: ["sh", "-c", "echo Initializing... && sleep 10"]

kubectl get pod <pod-name> -n <namespace> -o jsonpath='{range .status.containerStatuses[*]}{.name}{"\t"}{.state}{"\n"}{end}'

kubectl logs <pod_name> -c <container_name>

Restart policy

1. Always: (deafault -> k8s try to restart if pod or container failed)
2. Never: (never restart)
3. OnFailure: Restart pod when if its failled when status code is not equal to 0

Task:

1. create sample yaml for pod image tomcat:latest port: 8080
2. add init container

initContainers:
    - name: init-sample-data
      image: busybox:latest
      command: ["sh", "-c", "echo Initializing demo... && sleep 5"]

3. check logs and describe pod to validate state