Readwriteonce Vs Readwritemany¶

Introduction¶

This guide explains readwriteonce vs readwritemany with practical kubectl commands, realistic output, and production-focused checks. Configuration and storage problems often appear as pod startup failures, missing files, stale environment variables, or PVCs stuck in Pending.

When You Need This¶

Use this guide when an application needs configuration, credentials, mounted files, persistent data, or storage provisioning.

Example Manifest¶

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
  namespace: app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: web
        image: nginx:1.27
        ports:
        - containerPort: 80

Apply and Inspect¶

kubectl get pods -A
kubectl get events -A --sort-by=.lastTimestamp
kubectl explain pod.spec.containers
kubectl get all -n app
kubectl describe deployment web -n app

Expected output:

NAMESPACE   NAME                     READY   STATUS    RESTARTS   AGE
app         pod/web-7d9f8c-abcde     1/1     Running   0          2d

Verification¶

kubectl describe pod web-0 -n app
kubectl exec -n app web-0 -- ls -l /etc/config || true
kubectl get events -n app --sort-by=.lastTimestamp

Troubleshooting¶

Check object names, namespace, volumeMount paths, subPath behavior, secret type, PVC access mode, StorageClass, and provisioner events.

Common Mistakes¶

• Updating a ConfigMap and expecting existing environment variables to change without restarting pods.
• Mounting a Secret or ConfigMap from the wrong namespace.
• Troubleshooting PVC Pending without checking StorageClass and provisioner events.

Quick Checklist¶

• Confirm object exists in the same namespace.
• Check pod volume and volumeMount names.
• Inspect events for mount or provisioning errors.
• Restart pods when environment-based config changes.
• Protect Secrets with RBAC and least privilege.

Related Guides¶

• PVC Pending Troubleshooting
• Secret Security Best Practices
• Mount PVC To Pod
• Storage Troubleshooting Kubernetes

Summary¶

Config, secret, and storage issues are usually visible in pod events. Confirm the object, namespace, mount path, and storage binding before changing the workload.