193 lines
4.2 KiB
Markdown
193 lines
4.2 KiB
Markdown
# 🌐 Kubernetes Persistent Volumes (PV) Cheat Sheet
|
||
|
||
## 📦 What is a Persistent Volume (PV)?
|
||
|
||
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**.
|
||
|
||
---
|
||
|
||
## 📁 PV Storage Options
|
||
|
||
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):** 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)** – The actual storage unit.
|
||
2. **Persistent Volume Claim (PVC)** – A request for that storage.
|
||
|
||
---
|
||
|
||
## 🔄 PV Lifecycle States
|
||
|
||
| 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** – Multiple nodes read-only |
|
||
| `RWX` | **ReadWriteMany** – Multiple nodes read/write |
|
||
| `RWOP` | **ReadWriteOncePod** – Only one Pod can use it |
|
||
|
||
---
|
||
|
||
## 🛠️ 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 1: Deployment with `hostPath` Volume
|
||
|
||
```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
|
||
hostPath:
|
||
path: /root/nginx/logs
|
||
type: DirectoryOrCreate
|
||
```
|
||
|
||
---
|
||
|
||
## 📂 Example 2: NFS-backed Persistent Volume
|
||
|
||
### 🧩 PersistentVolume Definition
|
||
|
||
```yaml
|
||
apiVersion: v1
|
||
kind: PersistentVolume
|
||
metadata:
|
||
name: pv1
|
||
spec:
|
||
capacity:
|
||
storage: 5Gi
|
||
volumeMode: Filesystem
|
||
accessModes:
|
||
- ReadWriteMany
|
||
persistentVolumeReclaimPolicy: Retain
|
||
storageClassName: custom-name
|
||
mountOptions:
|
||
- hard
|
||
- nfsvers=4.1
|
||
nfs:
|
||
path: /nfs/data
|
||
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
|
||
|