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kuber doc: pv and pvc

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Containerization & Orchestration/Kubernetes/workloads/11-Pv.md
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@@ -1,12 +1,13 @@
Here's a clean, organized, and visually appealing document version of your input on **Persistent Volumes (PV) in Kubernetes**:
---
# 🌐 Kubernetes: Persistent Volumes (PV) Cheat Sheet
# 🌐 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**.
A **Persistent Volume (PV)** is a piece of storage in a Kubernetes cluster that is either:
* Pre-provisioned by an administrator, or
* Dynamically provisioned using **StorageClasses**.
It allows data to **persist beyond the lifecycle of individual Pods**.
---
@@ -15,56 +16,64 @@ A **Persistent Volume** is a piece of storage in a Kubernetes cluster that has b
1. **HostPath**
* Mounts a file or directory from the host node’s filesystem into your Pod.
* Useful only for single-node testing or development.
2. **Using PV and PVC**
* **PV (Persistent Volume):** The actual storage resource.
* **PVC (Persistent Volume Claim):** A request for storage by a user.
* **PV (Persistent Volume):** Represents the actual storage resource.
* **PVC (Persistent Volume Claim):** A user's request for storage resources and access.
---
## 🧱 Kubernetes Storage Layers
1. **Persistent Volume (PV)**
2. **Persistent Volume Claim (PVC)**
1. **Persistent Volume (PV)** – The actual storage unit.
2. **Persistent Volume Claim (PVC)** – A request for that storage.
---
## 🔄 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 |
| State | Description |
| ------------ | ------------------------------------------ |
| Provisioning | PV is being prepared. |
| Binding | PV is bound to a PVC. |
| Using | PV is in use by a Pod. |
| Releasing | PVC is deleted; PV becomes unbound. |
| Reclaiming | Reclaim policy is applied: |
| | • `Delete` – Remove the storage. |
| | • `Recycle` – Basic scrub (deprecated). |
| | • `Retain` – Manual intervention required. |
---
## 🔒 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 |
| Mode | Description |
| ------ | ---------------------------------------------- |
| `RWO` | **ReadWriteOnce** – One node can read/write |
| `ROX` | **ReadOnlyMany** – Multiple nodes read-only |
| `RWX` | **ReadWriteMany** – Multiple nodes read/write |
| `RWOP` | **ReadWriteOncePod** – Only one Pod can use it |
---
## 🛠️ Check PVs via CLI
## 🛠️ CLI Commands to Manage PVs
```bash
# List all Persistent Volumes
kubectl get pv
# List all Persistent Volume Claims
kubectl get pvc
# Edit a PVC
kubectl edit pvc -n <namespace> <pvc-name>
```
---
## 🚀 Example: Deployment using HostPath Volume
## 🚀 Example 1: Deployment with `hostPath` Volume
```yaml
apiVersion: apps/v1
@@ -73,18 +82,16 @@ metadata:
name: app-1
namespace: dev
labels:
label1: test1
app.kubernetes.io/label2: test2
app.kubernetes.io/name: nginx
spec:
replicas: 3
selector:
matchLabels:
app.kubernetes.io/label2: test2
app.kubernetes.io/name: nginx
template:
metadata:
labels:
app.kubernetes.io/label2: test2
os: linux
app.kubernetes.io/name: nginx
spec:
containers:
- name: nginx
@@ -98,11 +105,14 @@ spec:
- name: nginx-log
hostPath:
path: /root/nginx/logs
type: DirectoryOrCreate
```
---
## 📂 Example: PersistentVolume with NFS
## 📂 Example 2: NFS-backed Persistent Volume
### 🧩 PersistentVolume Definition
```yaml
apiVersion: v1
@@ -115,7 +125,7 @@ spec:
volumeMode: Filesystem
accessModes:
- ReadWriteMany
persistentVolumeReclaimPolicy: Recycle
persistentVolumeReclaimPolicy: Retain
storageClassName: custom-name
mountOptions:
- hard
@@ -125,3 +135,58 @@ spec:
server: 192.168.1.10
```
### 📄 PersistentVolumeClaim
```yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: pvc1
namespace: ns-test
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 1Gi
storageClassName: custom-name
```
### 🚀 Deployment Using PVC
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: app-1
namespace: dev
labels:
app.kubernetes.io/name: nginx
spec:
replicas: 3
selector:
matchLabels:
app.kubernetes.io/name: nginx
template:
metadata:
labels:
app.kubernetes.io/name: nginx
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 80
volumeMounts:
- name: nginx-log
mountPath: /var/log/nginx
volumes:
- name: nginx-log
persistentVolumeClaim:
claimName: pvc1
```
---
## 📝 Common Mistakes Fixed