CKA Exam = Storage 10%

 

• Understand storage classes, persistent volumes

• Understand volume mode, access modes and reclaim policies for volumes

• Understand persistent volume claims primitive

• Know how to configure applications with persistent storage

If you are interested to learn Volume then you may go through the below videos at the end of this page. However, if you're interested only for CKA exam then follow me.

In exam, they may ask to you to create PV, after that create PVC and bound this PVC with PV that you created earlier. Further, they may ask to create pod and then mount this PVC. 

Let's take an example of some questions.

Question .

 - Create a new PersistentVolume named tata-pv. It should have a capacity of 2Gi, accessMode ReadWriteOnce, hostPath /srv/app-config-var.

 - Next create a new PersistentVolumeClaim in Namespace project-tiger named tata-pvc . It should request 2Gi storage, accessMode ReadWriteOnce and should not define a storageClassName. The PVC should bound to the PV correctly.

 - Finally create a new pod tata in Namespace project-tiger which mounts that volume at /tmp/tata-data. The Pods should be of image httpd:2.4.41-alpine.

Solution: In exam, namespace "project-tige" already created. 

To complete this question, we need to create PV, PVC and POD.

1. Create PV:  

name=tata-pv,  

Capacity=2Gi, 

accessMode=ReadWriteOnce, 

hostPath=/srv/app-config-var , 

Remember: PV is not namespaced object.

 

2. Create PVC: 

name=tata-pvc, 

Capacity=2Gi,

 accessMode=ReadWriteOnce, 

Namespace=project-tiger, 

should not define a storageClassName.

 

3. Create POD: 

name=tata, 

namespace=project-tiger, 

volume=/tmp/tata-data, 

image=httpd:2.4.41-alpine

1. Create PV:  name=tata-pv,  Capacity=2Gi, accessMode=ReadWriteOnce, hostPath=/srv/app-config-var , Remember: PV is not namespaced object.

 

Open kubernetes.io => Documentation => Search "pv hostPath"

 Copy content like below from the website.

 

Copy the below content	Remove the lines	Our final file
apiVersion: v1 kind: PersistentVolume metadata:   name: task-pv-volume   labels:     type: local spec:   storageClassName: manual   capacity:     storage: 10Gi   accessModes:     - ReadWriteOnce   hostPath:     path: "/mnt/data"	apiVersion: v1 kind: PersistentVolume metadata:   name: tata-pv   labels:     type: local spec:   storageClassName: manual   capacity:     storage: 2Gi   accessModes:     - ReadWriteOnce   hostPath:     path: "/srv/app-config-var"	apiVersion: v1 kind: PersistentVolume metadata:   name: tata-pv spec:   capacity:     storage: 2Gi   accessModes:     - ReadWriteOnce   hostPath:     path: "/srv/app-config-var"

 

 

cat <<EOF>> question7-pv.yaml

apiVersion: v1
kind: PersistentVolume
metadata:
  name: tata-pv
spec:
  capacity:
    storage: 2Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/srv/app-config-var"

EOF

 

2. Create PVC: name=tata-pvc, Capacity=2Gi, accessMode=ReadWriteOnce, Namespace=project-tiger, should not define a storageClassName.

 

 kubernetes.io => Documentation => Search "pvc accessModes"

 Open the first link.

Copy the below content	Remove the lines	Our final file
apiVersion: v1 kind: PersistentVolumeClaim metadata:   name: restore-pvc spec:   storageClassName: csi-hostpath-sc   dataSource:     name: new-snapshot-test     kind: VolumeSnapshot     apiGroup: snapshot.storage.k8s.io   accessModes:     - ReadWriteOnce   resources:     requests:       storage: 10Gi	apiVersion: v1 kind: PersistentVolumeClaim metadata:   name: tata-pvc   namespace: project-tiger spec:   storageClassName: csi-hostpath-sc   dataSource:     name: new-snapshot-test     kind: VolumeSnapshot     apiGroup: snapshot.storage.k8s.io   accessModes:     - ReadWriteOnce   resources:     requests:       storage: 10Gi	apiVersion: v1 kind: PersistentVolumeClaim metadata:   name: tata-pvc   namespace: project-tiger spec:   accessModes:     - ReadWriteOnce   resources:     requests:       storage: 2Gi

 

cat <<EOF>> question7-pvc.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: tata-pvc
  namespace: project-tiger
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi

EOF

 

3. Create pod: name=tata, namespace=project-tiger, volume=/tmp/tata-data, image=httpd:2.4.41-alpine

 

 kubernetes.io => Documentation => Search "pod pvc"

 

 

Copy the below content	Remove the lines	Our final file
apiVersion: v1 kind: Pod metadata:   name: task-pv-pod spec:   volumes:     - name: task-pv-storage       persistentVolumeClaim:         claimName: task-pv-claim   containers:     - name: task-pv-container       image: nginx       ports:         - containerPort: 80           name: "http-server"       volumeMounts:         - mountPath: "/usr/share/nginx/html"           name: task-pv-storage	apiVersion: v1 kind: Pod metadata:   name: tata   namespace: project-tiger spec:   volumes:     - name: data       persistentVolumeClaim:         claimName: tata-pvc   containers:     - name: task-pv-container       image: httpd:2.4.41-alpine       ports:         - containerPort: 80           name: "http-server"       volumeMounts:         - mountPath: "/tmp/tata-data"           name: data	apiVersion: v1 kind: Pod metadata:   name: tata   namespace: project-tiger spec:   volumes:     - name: data       persistentVolumeClaim:         claimName: tata-pvc   containers:     - name: task-pv-container       image: httpd:2.4.41-alpine       volumeMounts:         - mountPath: "/tmp/tata-data"           name: data

 

 

cat <<EOF>> question7-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: tata
  namespace: project-tiger
spec:
  volumes:
    - name: data
      persistentVolumeClaim:
        claimName: tata-pvc
  containers:
    - name: task-pv-container
      image: httpd:2.4.41-alpine
      volumeMounts:
        - mountPath: "/tmp/tata-data"
          name: data
EOF

 

kubectl apply -f  question7-pv.yaml

kubectl apply -f  question7-pvc.yaml

kubectl apply -f  question7-pod.yaml

 

Post checks: How to check if our volume is mounted on this POD?

 [root@master1 ~]# kubectl -n project-tiger get pods
NAME   READY   STATUS    RESTARTS   AGE
tata   1/1     Running   0          50s
 

[root@master1 ~]# kubectl -n project-tiger exec -it tata -- /bin/bash

bash-5.0# df -h
Filesystem                Size      Used Available Use% Mounted on
overlay                  14.0G      8.3G      5.6G  60% /
tmpfs                    64.0M         0     64.0M   0% /dev
/dev/sda2                14.0G      8.3G      5.6G  60% /tmp/tata-data
/dev/sda2                14.0G      8.3G      5.6G  60% /etc/hosts
/dev/sda2                14.0G      8.3G      5.6G  60% /dev/termination-log
/dev/sda2                14.0G      8.3G      5.6G  60% /etc/hostname
/dev/sda2                14.0G      8.3G      5.6G  60% /etc/resolv.conf
shm                      64.0M         0     64.0M   0% /dev/shm
tmpfs                     2.1G     12.0K      2.1G   0% /run/secrets/kubernetes.io/serviceaccount
tmpfs                     1.1G         0      1.1G   0% /proc/acpi
tmpfs                    64.0M         0     64.0M   0% /proc/kcore
tmpfs                    64.0M         0     64.0M   0% /proc/keys
tmpfs                    64.0M         0     64.0M   0% /proc/timer_list
tmpfs                     1.1G         0      1.1G   0% /proc/scsi
tmpfs                     1.1G         0      1.1G   0% /sys/firmware
bash-5.0#

 

bash-5.0# ls -ltr /tmp/tata-data
total 0

 

 

 From starting to end, please watch below video.

 

 

 

 

 

Question : Create a persistent volume with name app-motor, of capacity 2Gi and access mode ReadWriteMany. The type of volume is hostPath location is /srv/app-tata

Soloution: 

kubectl config use-context ek8s

 In this question, it is asked us to create only PV, thus we will only create PV.

Open URL : https://kubernetes.io --> Documentation --> Search => PV Accessmode ==> Open first link and search for "accessmode"

Copy the content link below:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv0003
spec:
  capacity:
    storage: 5Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Recycle
  storageClassName: slow
  mountOptions:
    - hard
    - nfsvers=4.1
  nfs:
    path: /tmp
    server: 172.17.0.2

Now, modify the Yaml file as per the question

[root@master1 ~]# cat <<EOF>> question8-pv.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: app-motor
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 2Gi
  accessModes:
    - ReadWriteMany
  hostPath:
    path: "/srv/app-tata"
EOF

[root@master1 ~]# kubectl apply -f question8-pv.yaml
persistentvolume/app-motor created



[root@master1 ~]# kubectl get pv/app-motor
NAME        CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
app-motor   2Gi        RWX            Retain           Available           manual                  14m

You can also check this PV by describe sub-command. It gives you more details.

[root@master1 ~]# kubectl describe pv/app-motor
Name:            app-motor
Labels:          type=local
Annotations:     <none>
Finalizers:      [kubernetes.io/pv-protection]
StorageClass:    manual
Status:          Available
Claim:           
Reclaim Policy:  Retain
Access Modes:    RWX
VolumeMode:      Filesystem
Capacity:        2Gi
Node Affinity:   <none>
Message:         
Source:
    Type:          HostPath (bare host directory volume)
    Path:          /srv/app-tata
    HostPathType:  
Events:            <none>
[root@master1 ~]#

If you want to learn hostPath volume then you may watch my Youtube video.

https://youtu.be/oRDBzoorybI