Static and Dynamic PV for PVC in Kubernetes.

A). How Static Persistent Volume (PV) and Persistent Volume Claim (PVC) work with HostPath in Kubernetes.

•  A hostPath volume mounts a file or directory from the host node’s filesystem into your pod.
• A hostPath PersistentVolume must be used only in a single-node cluster. Kubernetes does not support hostPath on a multi-node cluster currently.

i) First create a PV for hostpath.

# hostpath-pv.yaml

apiVersion: v1

kind: PersistentVolume

metadata:

  name: pv-hostpath

  labels:

    type: local

spec:

  storageClassName: manual

  capacity:

    storage: 1Gi

  accessModes:

    - ReadWriteOnce

  hostPath:

    path: "/shashi_data"

# kubectl apply -f hostpath-pv.yaml

# kubectl get pv

ii) Create a PVC for hostpath.

# cat hostpath-pvc.yaml

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  name: pvc-hostpath

spec:

  storageClassName: manual

  accessModes:

    - ReadWriteOnce

  resources:

    requests:

      storage: 100Mi

# kubectl apply -f hostpath-pvc.yaml

# kubectl  get  pvc

iii) create a pod with hostpath. 

# cat busy_box.yaml

apiVersion: v1

kind: Pod

metadata:

  name: busybox

spec:

  volumes:

  - name: host-volume

    persistentVolumeClaim:

      claimName: pvc-hostpath

  containers:

  - image: busybox

    name: busybox

    command: ["/bin/sh"]

    args: ["-c", "sleep 600"]

    volumeMounts:

    - name: host-volume

      mountPath: /mydata

# kubectl apply -f busy_box.yaml

# kubectl get pods -o wide

# kubectl exec busybox -- ls /mydata

# kubectl exec busybox -- touch /mydata/test123

go to woker2 node.

# ls /shashi_data/

B). How to schedule HostPath in select nodes?

# kubectl apply -f hostpath-pv.yaml

# kubectl apply -f hostpath-pvc.yaml

Check node labels.

# kubectl get node worker1 --show-labels

Labels are added at the woker1 node.

# kubectl label node worker1 node_worker=true

# kubectl get node worker1 --show-labels

# vim busy_box.yaml

# kubectl apply -f busy_box.yaml

# kubectl get pods -o wide

# kubectl exec busybox -- touch /mydata/test71

# kubectl exec busybox -- ls /mydata

test71

# ls /shashi_data/

C). How to reuse a PersistentVolume (PV) in kubernetes.

By default, PVs have a reclaim policy of Retain, which means the PV is not automatically deleted or made available for reuse when the PVC is deleted.

# kubectl apply -f hostpath-pvc.yaml

How to fix “manual not found” Error

Edit the PV to remove the claimRef field, which ties the PV to the previous PVC:

# kubectl edit  pv pv-hostpath

# kubectl get pv

# kubectl apply -f hostpath-pvc.yaml

# kubectl get pv

# kubectl get pvc

# kubectl describe pvc pvc-hostpath

D). Create Static Persistent Volume PV and PVC for EBS AWS. 

1.We will manually create EBS volumes and create volumes in the same zone (Availability Zone : us-east-2b) as the cluster node.

2. Mount the volume vol-0cf28e25fd0db918e in the node and format the volume with ext4 filesystem. Will then Detach Volume  from node.

Disk → PV →  PVC ← Pods

i) Create a PV for  ebs . 

# vim ebs-pv.yaml

# kubectl  apply -f ebs-pv.yaml

# kubectl get pv

ii) Create a PVC for  ebs . 

#vim  ebs-pvc.yaml

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  labels:

    app: mysql

  name: pvc

spec:

  accessModes:

  - ReadWriteOnce

  resources:

    requests:

      storage: 10Gi

  storageClassName: gp2

  volumeMode: Filesystem

  volumeName: pv-ebs-static

# kubectl  apply -f ebs-pvc.yaml

# kubectl get pvc

iii) Create a Pods for  ebs . 

# vim nginx.yaml 

apiVersion: v1

kind: Pod

metadata:

  name: nginx

spec:

  containers:

    - name: nginx

      image: nginx:latest

      ports:

        - name: http

          containerPort: 80

      volumeMounts:

        - name: data

          mountPath: /usr/share/nginx/html

  volumes:

    - name: data

      persistentVolumeClaim:

        claimName: pvc

# kubectl  apply -f nginx.yaml

# kubectl get pv,pvc,pods

# kubectl  exec -it nginx /bin/bash
# touch /usr/share/nginx/html/test.txt

E). Create Dynamic PVC and StorageClass for EBS AWS. 

reclaimPolicy: Unsupported value: "Recycle": supported values: "Delete", "Retain"

Disk ← storageClass ← PVC ← Pods

i) Create a storageClass.

# vim storageclass.yaml

kind: StorageClass

apiVersion: storage.k8s.io/v1

metadata:

  name: mystorageclass

provisioner: kubernetes.io/aws-ebs

parameters:

  type: gp2

  iopsPerGB: "10"

  fsType: ext4

reclaimPolicy: Delete

mountOptions:

  - debug

# kubectl apply -f  storageclass.yaml

# kubectl get sc

 

ii) Create a pvc for mysql.

# vim ebs-pvc_test.yaml

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  labels:

    app: mysql

  name: pvc

spec:

  accessModes:

  - ReadWriteOnce

  resources:

    requests:

      storage: 10Gi

  storageClassName: mystorageclass

 

# kubectl apply -f ebs-pvc_test.yaml

# kubectl get pvc

 

iii) Create a pods.

# vim nginx.yaml

apiVersion: v1

kind: Pod

metadata:

  name: nginx

spec:

  containers:

    - name: nginx

      image: nginx:latest

      ports:

        - name: http

          containerPort: 80

      volumeMounts:

        - name: data

          mountPath: /usr/share/nginx/html

  volumes:

    - name: data

      persistentVolumeClaim:

        claimName: pvc

# kubectl apply -f nginx.yaml

# kubectl get pods,pv,pvc

# kubectl describe  pods nginx 

F). How to Allow Multiple Pods to Read/Write in AWS EFS Storage in Kubernetes.

1.In the security group for EFS will be allowed worker nodes Ips.

2. Click Attach Option its showing the access point URL.

3.if security group change in efs:-

              Network → manage → change security group.

4.install “sudo apt install nfs-common” in all node workers.

https://github.com/antonputra/tutorials/tree/main/lessons/041

# mkdir efs

# cd efs

1-namespace.yaml

2-service-account.yaml

3-clusterrole.yaml

4-clusterrolebinding.yaml

5-role.yaml

6-rolebinding.yaml

7-deployment.yaml

 

8-storage-class.yaml

# mkdir test

# cd test

1-namespace.yaml

2-persistent-volume-claim.yaml

3-foo-deployment.yaml

4-bar-deployment.yaml

# testing 

Run below command on woker1 and worker2 and data is available in below path on woker nodes.

# mount | grep “nfs” 

###### Dynamic PV and PVC with NFS on-premise  ###  

1️.Set up an NFS server (if not already available)
2️.Deploy the NFS CSI Driver
3️.Create an NFS StorageClass (for dynamic provisioning)
4️.Create a PersistentVolumeClaim (PVC)
5️.Deploy a Pod using the dynamically provisioned volume

 

1.Set up an NFS server (if not already available)

showmount -e <NFS_SERVER_IP>

2.Install the NFS CSI Driver in Kubernetes.

Kubernetes CSI (Container Storage Interface) driver for NFS.

Provisioner Name: nfs.csi.k8s.io

# helm repo add csi-driver-nfs https://raw.githubusercontent.com/kubernetes-csi/csi-driver-nfs/master/charts

# helm repo update

# helm repo list

# helm install nfs-csi csi-driver-nfs/csi-driver-nfs --namespace kube-system --create-namespace

# helm list -n kube-system

Note:- If remove repo from helm.  

# helm repo remove csi-driver-nfs

Note:- If remove nfs csi driver

# helm uninstall nfs-csi -n kube-system

Pods is created for CSI-NFS driver.

# kubectl get pods -n kube-system | grep nfs

 

CSI Driver is showing.

# kubectl get csidrivers

 

On which nodes is the CSI driver installed.

#kubectl get csinodes

 

3️.Create an NFS StorageClass.

apiVersion: storage.k8s.io/v1

kind: StorageClass

metadata:

  name: nfs-csi

provisioner: nfs.csi.k8s.io

parameters:

  server: <NFS_SERVER_IP>   # Replace with actual NFS server IP

  share: /exported/nfs-data       # Path to NFS shared directory

reclaimPolicy: Retain

volumeBindingMode: Immediate

allowVolumeExpansion: true

# kubectl apply -f storageclass-nfs.yaml

# kubectl get storageclass

Or

# kubectl get sc

 

5.Create a PersistentVolumeClaim (PVC).

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  name: nfs-pvc

spec:

  accessModes:

    - ReadWriteMany

  resources:

    requests:

      storage: 5Gi

  storageClassName: nfs-csi

 

# kubectl apply -f pvc.yaml

# kubectl get pvc

# kubectl get pv

 

6.Deploy a Pod Using the Dynamically Provisioned Volume.

apiVersion: v1

kind: Pod

metadata:

  name: nfs-test-pod

spec:

  containers:

  - name: busybox

    image: busybox

    command: [ "sleep", "3600" ]

    volumeMounts:

    - mountPath: "/mnt/nfs"

      name: nfs-volume

  volumes:

  - name: nfs-volume

    persistentVolumeClaim:

      claimName: nfs-pvc

 

# kubectl apply -f pod.yaml

# kubectl get pods

# kubectl get pv,pvc

 

Verification :-

1️.Check Mounted Storage Inside the Pod

# kubectl exec -it nfs-test-pod -- df -h /mnt/nfs

2️.Create a Test File to Verify Persistence

kubectl exec -it nfs-test-pod -- touch /mnt/nfs/testfile.txt

Check  the nfs  Node:

 

Multiple pvc volume in nfs path.

# ls /exported/nfs-data/<volume>

# ls /exported/nfs-data/pvc-819ab3b0-18a0-4f33-beb5-747530c01957/

 

Note :-

1.If the pod is deleted and recreated it will use the same PVC volumes.

2.If PVC volumes are deleted and PVC volumes are created, a new PVC ID is created.

3. ReclaimPolicy: Delete parameter then if PVC is deleted then PV will also be deleted. (all data).

# kubectl get pv,pvc