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Objects in K8S

Pod

  • The smallest deployable unit in Kubernetes.
  • Represent a single instance of running processes in your cluster
  • Can contain one or more containers that share storage and network
  • Pods that run a single container
    • The "one-container-per-pod" model is the most common Kubernetes use case (Kubernetes manages the Pods rather than the containers directly).
  • Multi Container POD
    • Tightly coupled and need to share resources
    • One main container and other as sidecar or init container (or both)
    • Each Pod is meant to run a single instance of a given application
    • Should use multiple Pods to scale horizontally

Definitions file in example similar to docker compose / docker run. pod-setup.yml

apiVersion: v1
kind: Pod
metadata:
  name: webapp-pod
  labels:
    app: frontend
    project: infinity
spec:
  containers:
    - name: httpd-container
      image: httpd
      imagePullPolicy: IfNotPresent
      ports:
        - name: http-port
          containerPort: 8080 # exposed port

Then to create the pod run this command: 

kubectl create -f pod-setup.yml

Use commands below to get info

kubectl get pod
kubectl describe pod webapp-pod
kubectl get pod webapp-pod -o yaml
kubectl get pod webapp-pod -o yaml > webpod-definition.yml

Edit pod webapp-pod

kubectl edit webapp-pod

Type of Kind:

Kind API Version
Pod v1
Service v1
Deployment apps/v1
Ingress networking.k8s.io/v1

Pods docs

Service

  • Provides a stable network endpoint to access Pods.
  • Supports different types: ClusterIP (default), NodePort, LoadBalancer, and ExternalName.
  • Enables load balancing across multiple Pod replicas.

Replica Set

  • Ensures a specified number of Pod replicas are running at any given time.
  • Automatically replaces failed or terminated Pods to maintain the desired count.

Deployment

  • Provides declarative updates for Pods and ReplicaSets.
  • Manages rollouts and rollbacks of application versions.
  • Supports updating container images via image tags.

Config Map

  • Stores non-sensitive configuration data as key-value pairs.
  • Used to decouple configuration artifacts from application code.
  • Can inject data into Pods as environment variables, command-line arguments, or configuration files.

Secret

  • Stores sensitive data (e.g., passwords, tokens, SSH keys) in base64-encoded format.
  • Prevents exposing sensitive information in plain text.
  • Can be mounted as files or exposed as environment variables in Pods.

Volumes

  • Provide persistent or temporary storage for Pods.

  • Volume types include:

    • emptyDir – Temporary storage shared between containers in a Pod.
    • hostPath – Mounts a file or directory from the host node.
    • persistentVolumeClaim (PVC) – Abstraction for durable storage, often backed by cloud storage solutions.
    • configMap/secret – Mount configuration or secret data as files.
    • nfs, csi, awsElasticBlockStore, etc. – Other network and cloud-specific storage options.