my-docs/Containerization-Orchestration/Kubernetes/Storage/pv-pvc.md

🌐 Kubernetes: Persistent Volumes (PV) Cheat Sheet

📦 What is a Persistent Volume (PV)?

A Persistent Volume is a piece of storage in a Kubernetes cluster that has been provisioned by an administrator or dynamically provisioned using StorageClasses.

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📁 PV Storage Options

1. HostPath

   • Mounts a file or directory from the host node’s filesystem into your Pod.

2. Using PV and PVC

   • PV (Persistent Volume): The actual storage resource.
   • PVC (Persistent Volume Claim): A request for storage by a user.

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🧱 Kubernetes Storage Layers

1. Persistent Volume (PV)
2. Persistent Volume Claim (PVC)

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🔄 PV Lifecycle States

State	Description
Provisioning	Kubernetes is preparing the PV.
Binding	The PV is bound to a PVC.
Using	The bound PV is being used by a Pod.
Releasing	PVC is deleted; PV is no longer bound.
Reclaiming	PV is reclaimed using one of the following policies:
	• Delete – Remove the storage
	• Recycle – Basic scrub (deprecated)
	• Retain – Manual reclaim

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🔒 PV Access Modes

Mode	Description
RWO	ReadWriteOnce – One node can read/write
ROX	ReadOnlyMany – Many nodes read-only
RWX	ReadWriteMany – Many nodes read/write
RWOP	ReadWriteOncePod – One Pod only

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🛠️ Check PVs via CLI

kubectl get pv

kubectl get pvc

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🚀 Example: Deployment using HostPath Volume

apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-1
  namespace: dev
  labels:
    label1: test1
    app.kubernetes.io/label2: test2
spec:
  replicas: 3
  selector:
    matchLabels:
      app.kubernetes.io/label2: test2
  template:
    metadata:
      labels:
        app.kubernetes.io/label2: test2
        os: linux
    spec:
      containers:
        - name: nginx
          image: nginx
          ports:
            - containerPort: 80
          volumeMounts:
            - name: nginx-log
              mountPath: /var/log/nginx  
      volumes:
        - name: nginx-log
          hostPath:
            path: /root/nginx/logs

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📂 Example: PersistentVolume with NFS

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv1
spec:
  capacity: 
    storage: 5Gi
  volumeMode: Filesystem
  accessModes: 
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Recycle
  storageClassName: custom-name
  mountOptions:
    - hard
    - nfsvers=4.1
  nfs:
    path: /nfs/data
    server: 192.168.1.10

apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-1
  namespace: dev
  labels:
    label1: test1
    app.kubernetes.io/label2: test2
spec:
  replicas: 3
  selector:
    matchLabels:
      app.kubernetes.io/label2: test2
  template:
    metadata:
      labels:
        app.kubernetes.io/label2: test2
        os: linux
    spec:
      containers:
        - name: nginx
          image: nginx
          ports:
            - containerPort: 80
          volumeMounts:
            - name: nginx-log
              mountPath: /var/log/nginx  
          volumes:
            - name: nginx-log
              persisentVolumeClaim:
                claimName: pv1
---

apiVersion: v1
kind: persisentVolumeClaim
metadata:
    name: pvc1
    namespace: ns-test
spec:
    accessModes: 
        - ReadWriteMany
    resources:
        requests:
            storage: 1Gi
        limits:
            storage: 2Gi        
    storageClassName: custom-name