CKA Exam Dumps : Certified Kubernetes Administrator (CKA) Program

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Persistent Volume

A persistent volume is a piece of storage in a Kubernetes cluster. PersistentVolumes are a cluster-level resource like nodes, which don’t belong to any namespace. It is provisioned by the administrator and has a particular file size. This way, a developer deploying their app on Kubernetes need not know the underlying infrastructure. When the developer needs a certain amount of persistent storage for their application, the system administrator configures the cluster so that they consume the PersistentVolume provisioned in an easy way.

Creating Persistent Volume

kind: PersistentVolume

apiVersion: v1

metadata:

name:app-data

spec:

capacity: # defines the capacity of PV we are creating

storage: 2Gi #the amount of storage we are tying to claim

accessModes: # defines the rights of the volume we are creating

- ReadWriteMany

hostPath:

path: "/srv/app-data" # path to which we are creating the volume

Challenge

Create a Persistent Volume named app-data, with access mode ReadWriteMany, storage classname shared, 2Gi of storage capacity and the host path /srv/app-data.

2. Save the file and create the persistent volume.

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3. View the persistent volume.

Our persistent volume status is available meaning it is available and it has not been mounted yet. This status will change when we mount the persistentVolume to a persistentVolumeClaim.

PersistentVolumeClaim

In a real ecosystem, a system admin will create the PersistentVolume then a developer will create a PersistentVolumeClaim which will be referenced in a pod. A PersistentVolumeClaim is created by specifying the minimum size and the access mode they require from the persistentVolume.

Challenge

Create a Persistent Volume Claim that requests the Persistent Volume we had created above. The claim should request 2Gi. Ensure that the Persistent Volume Claim has the same storageClassName as the persistentVolume you had previously created.

kind: PersistentVolume

apiVersion: v1

metadata:

name:app-data

spec:

accessModes:

- ReadWriteMany

resources:

requests:

storage: 2Gi

storageClassName: shared

2. Save and create the pvc

njerry191@cloudshell:~ (extreme-clone-2654111)$ kubect1 create -f app-data.yaml

persistentvolumeclaim/app-data created

3. View the pvc

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4. Let’s see what has changed in the pv we had initially created.

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Our status has now changed from available to bound.

5. Create a new pod named myapp with image nginx that will be used to Mount the Persistent Volume Claim with the path /var/app/config.

Mounting a Claim

apiVersion: v1

kind: Pod

metadata:

creationTimestamp: null

name: app-data

spec:

volumes:

- name:congigpvc

persistenVolumeClaim:

claimName: app-data

containers:

- image: nginx

name: app

volumeMounts:

- mountPath: "/srv/app-data "

name: configpvc

Solution:

#backup

ETCDCTL_API=3 etcdctl --endpoints=" " --cacert=/opt/KUIN000601/ca.crt --cert=/opt/KUIN000601/etcd-client.crt --key=/opt/KUIN000601/etcd-client.key snapshot save /etc/data/etcd-snapshot.db

#restore

ETCDCTL_API=3 etcdctl --endpoints=" " --cacert=/opt/KUIN000601/ca.crt --cert=/opt/KUIN000601/etcd-client.crt --key=/opt/KUIN000601/etcd-client.key snapshot restore /var/lib/backup/etcd-snapshot-previoys.db

Task Summary

SSH into node: cka000059

Cluster was migrated to a new machine

It uses an external etcd server

Identify and fix misconfigured components

Bring the cluster back to a healthy state

Step-by-Step Solution

Step 1: SSH into the correct host

ssh cka000059

Step 2: Check the cluster status

Run:

kubectl get nodes

If it fails, the kubelet or kube-apiserver is likely broken.

Check kubelet status:

sudo systemctl status kubelet

Also, check pod statuses in the control plane:

sudo crictl ps -a | grep kube

or:

docker ps -a | grep kube

Look especially for failures in kube-apiserver or kube-controller-manager.

Step 3: Inspect the kube-apiserver manifest

Since this is a kubeadm-based cluster, manifests are in:

ls /etc/kubernetes/manifests

Open kube-apiserver.yaml:

bash

CopyEdit

sudo nano /etc/kubernetes/manifests/kube-apiserver.yaml

Look for the --etcd-servers= flag. If the external etcd endpoint has changed (likely, due to migration), this needs to be fixed.

Example of incorrect configuration:

If the IP has changed, update it to the correct IP or hostname of the external etcd server.

Also ensure the correct client certificate and key paths are still valid:

--etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt

--etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt

--etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key

If the files are missing or the path is wrong due to migration, correct those as well.

Step 4: Save and exit, and let static pod restart

Static pod changes will be picked up automatically by the kubelet (watch for /etc/kubernetes/manifests changes).

Check again:

docker ps | grep kube-apiserver

# or

crictl ps | grep kube-apiserver

Step 5: Confirm API is healthy

Once kube-apiserver is up, try:

kubectl get componentstatuses

kubectl get nodes

If these commands work and return valid statuses, the control plane is functional again.

Step 6: Check controller-manager and scheduler (optional)

If still broken, check the other static pods in /etc/kubernetes/manifests/ and correct paths if necessary.

Also verify that /etc/kubernetes/kubelet.conf and /etc/kubernetes/admin.conf are present and valid.

Command Summary

ssh cka000059

# Check system and kubelet

sudo systemctl status kubelet

docker ps -a | grep kube # or crictl ps -a | grep kube

# Check manifests

ls /etc/kubernetes/manifests

sudo nano /etc/kubernetes/manifests/kube-apiserver.yaml

# Fix --etcd-servers and certificate paths if needed

# Watch pods restart and confirm:

kubectl get nodes

kubectl get componentstatuses