kuber doc: pv and pvc
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Here's a clean, organized, and visually appealing document version of your input on **Persistent Volumes (PV) in Kubernetes**:
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# 🌐 Kubernetes Persistent Volumes (PV) Cheat Sheet
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# 🌐 Kubernetes: Persistent Volumes (PV) Cheat Sheet
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## 📦 What is a Persistent Volume (PV)?
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## 📦 What is a Persistent Volume (PV)?
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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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A **Persistent Volume (PV)** is a piece of storage in a Kubernetes cluster that is either:
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* Pre-provisioned by an administrator, or
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* Dynamically provisioned using **StorageClasses**.
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It allows data to **persist beyond the lifecycle of individual Pods**.
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---
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@@ -15,56 +16,64 @@ A **Persistent Volume** is a piece of storage in a Kubernetes cluster that has b
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1. **HostPath**
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1. **HostPath**
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* Mounts a file or directory from the host node’s filesystem into your Pod.
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* Mounts a file or directory from the host node’s filesystem into your Pod.
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* Useful only for single-node testing or development.
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2. **Using PV and PVC**
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2. **Using PV and PVC**
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* **PV (Persistent Volume):** The actual storage resource.
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* **PV (Persistent Volume):** Represents the actual storage resource.
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* **PVC (Persistent Volume Claim):** A request for storage by a user.
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* **PVC (Persistent Volume Claim):** A user's request for storage resources and access.
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---
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---
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## 🧱 Kubernetes Storage Layers
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## 🧱 Kubernetes Storage Layers
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1. **Persistent Volume (PV)**
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1. **Persistent Volume (PV)** – The actual storage unit.
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2. **Persistent Volume Claim (PVC)**
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2. **Persistent Volume Claim (PVC)** – A request for that storage.
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---
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---
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## 🔄 PV Lifecycle States
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## 🔄 PV Lifecycle States
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| State | Description |
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| State | Description |
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| ------------ | ---------------------------------------------------- |
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| ------------ | ------------------------------------------ |
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| Provisioning | Kubernetes is preparing the PV. |
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| Provisioning | PV is being prepared. |
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| Binding | The PV is bound to a PVC. |
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| Binding | PV is bound to a PVC. |
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| Using | The bound PV is being used by a Pod. |
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| Using | PV is in use by a Pod. |
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| Releasing | PVC is deleted; PV is no longer bound. |
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| Releasing | PVC is deleted; PV becomes unbound. |
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| Reclaiming | PV is reclaimed using one of the following policies: |
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| Reclaiming | Reclaim policy is applied: |
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| | • `Delete` – Remove the storage |
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| | • `Delete` – Remove the storage. |
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| | • `Recycle` – Basic scrub (deprecated) |
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| | • `Recycle` – Basic scrub (deprecated). |
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| | • `Retain` – Manual reclaim |
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| | • `Retain` – Manual intervention required. |
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---
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---
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## 🔒 PV Access Modes
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## 🔒 PV Access Modes
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| Mode | Description |
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| Mode | Description |
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| ------ | ------------------------------------------- |
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| ------ | ---------------------------------------------- |
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| `RWO` | **ReadWriteOnce** – One node can read/write |
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| `RWO` | **ReadWriteOnce** – One node can read/write |
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| `ROX` | **ReadOnlyMany** – Many nodes read-only |
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| `ROX` | **ReadOnlyMany** – Multiple nodes read-only |
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| `RWX` | **ReadWriteMany** – Many nodes read/write |
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| `RWX` | **ReadWriteMany** – Multiple nodes read/write |
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| `RWOP` | **ReadWriteOncePod** – One Pod only |
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| `RWOP` | **ReadWriteOncePod** – Only one Pod can use it |
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---
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---
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## 🛠️ Check PVs via CLI
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## 🛠️ CLI Commands to Manage PVs
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```bash
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```bash
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# List all Persistent Volumes
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kubectl get pv
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kubectl get pv
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# List all Persistent Volume Claims
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kubectl get pvc
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# Edit a PVC
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kubectl edit pvc -n <namespace> <pvc-name>
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```
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```
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---
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---
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## 🚀 Example: Deployment using HostPath Volume
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## 🚀 Example 1: Deployment with `hostPath` Volume
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```yaml
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```yaml
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apiVersion: apps/v1
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apiVersion: apps/v1
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name: app-1
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name: app-1
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namespace: dev
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namespace: dev
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labels:
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labels:
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label1: test1
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app.kubernetes.io/name: nginx
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app.kubernetes.io/label2: test2
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spec:
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spec:
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replicas: 3
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replicas: 3
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selector:
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selector:
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matchLabels:
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matchLabels:
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app.kubernetes.io/label2: test2
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app.kubernetes.io/name: nginx
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template:
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template:
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metadata:
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metadata:
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labels:
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labels:
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app.kubernetes.io/label2: test2
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app.kubernetes.io/name: nginx
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os: linux
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spec:
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spec:
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containers:
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containers:
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- name: nginx
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- name: nginx
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- name: nginx-log
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- name: nginx-log
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hostPath:
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hostPath:
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path: /root/nginx/logs
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path: /root/nginx/logs
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type: DirectoryOrCreate
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```
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```
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---
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---
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## 📂 Example: PersistentVolume with NFS
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## 📂 Example 2: NFS-backed Persistent Volume
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### 🧩 PersistentVolume Definition
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```yaml
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```yaml
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apiVersion: v1
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apiVersion: v1
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@@ -115,7 +125,7 @@ spec:
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volumeMode: Filesystem
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volumeMode: Filesystem
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accessModes:
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accessModes:
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- ReadWriteMany
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- ReadWriteMany
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persistentVolumeReclaimPolicy: Recycle
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persistentVolumeReclaimPolicy: Retain
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storageClassName: custom-name
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storageClassName: custom-name
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mountOptions:
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mountOptions:
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- hard
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- hard
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@@ -125,3 +135,58 @@ spec:
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server: 192.168.1.10
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server: 192.168.1.10
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```
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```
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### 📄 PersistentVolumeClaim
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```yaml
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apiVersion: v1
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kind: PersistentVolumeClaim
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metadata:
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name: pvc1
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namespace: ns-test
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spec:
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accessModes:
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- ReadWriteMany
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resources:
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requests:
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storage: 1Gi
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storageClassName: custom-name
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```
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### 🚀 Deployment Using PVC
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```yaml
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: app-1
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namespace: dev
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labels:
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app.kubernetes.io/name: nginx
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spec:
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replicas: 3
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selector:
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matchLabels:
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app.kubernetes.io/name: nginx
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template:
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metadata:
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labels:
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app.kubernetes.io/name: nginx
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spec:
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containers:
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- name: nginx
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image: nginx
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ports:
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- containerPort: 80
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volumeMounts:
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- name: nginx-log
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mountPath: /var/log/nginx
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volumes:
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- name: nginx-log
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persistentVolumeClaim:
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claimName: pvc1
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```
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---
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## 📝 Common Mistakes Fixed
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