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PODs

POD Definition

A pod definition file is used in Kubernetes to outline the pods and configuration involved in a deployment. Key configuration aspects to be defined within the pod definition file are:

Metadata Define pod name, labels, and annotations for identification.
Containers Specify the container's name, image, and pull policy.
Resource Allocation
  • Set requests (min resources) and limits (max resources) for CPU/memory.
Ports
  • Declare ports that the container exposes (e.g., containerPort: 80).
Environment Variables

Pass environment variables to the container.
Volume Mounts Mount persistent volumes or config files to the container.
Volumes Define storage (PersistentVolumeClaim, ConfigMap, or Secret).
Probes Health checks using liveness and readiness probes.
Command/Args Custom commands and arguments for container startup.
Affinity/Anti-Affinity Rules for scheduling the pod on specific nodes.
Node Selector Simple label-based node constraints for scheduling.
Security Context Set user/group IDs, filesystem permissions, and privilege levels.
DNS Policy
  • Set pod-specific DNS settings (e.g., ClusterFirst).
Restart Policy
  • Control when to restart the pod (e.g., Always, OnFailure).

Create pods based on pod definition:

kubectl create -f pod-definition.yaml

Apply new changes to existing pods:

kubectl apply -f pod-definition.yaml
Example pod definition file
apiVersion: #v1 API version defined
kind: Pod #kind defined as pod
metadata: #begin metadata definitions
  name: nginx-pod
  labels:
    app: webapp
spec: #Begin pod specification
  containers: #Pod containers
  - name: nginx #Container name
    image: nginx:latest #Container image
    ports: #Port configuration
    - containerPort: 80

 

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