Storage
Updated Dec 29, 2023 ·
Some of the scenario questions here are based on Kodekloud's CKA course labs.
NOTE
CKAD and CKA can have similar scenario questions. It is recommended to go through the CKAD practice tests.
Shortcuts
First run the two commands below for shortcuts.
export do="--dry-run=client -o yaml"
export now="--force --grace-period=0"
Questions
-
Configure a volume to store the webapp logs (stored at /log/app.log) at /var/log/webapp on the host. Use the spec provided below.
-
Name: webapp
-
Image Name: kodekloud/event-simulator
-
Volume HostPath: /var/log/webapp
-
Volume Mount: /log
Answer
controlplane ~ ➜ k get po
NAME READY STATUS RESTARTS AGE
webapp 1/1 Running 0 48s
controlplane ~ ➜ k exec -it webapp -- cat /log/app.log
[2023-12-30 11:51:39,293] INFO in event-simulator: USER3 is viewing page3
[2023-12-30 11:51:40,294] INFO in event-simulator: USER3 is viewing page3
[2023-12-30 11:51:41,295] INFO in event-simulator: USER3 is viewing page3
[2023-12-30 11:51:42,296] INFO in event-simulator: USER1 is viewing page1
[2023-12-30 11:51:43,297] INFO in event-simulator: USER1 is viewing page2
[2023-12-30 11:51:44,298] WARNING in event-simulator: USER5 Failed to Login as the account is locked due to MANY FAILED ATTEMPTS.Generate a YAML file first and then delete the pod.
controlplane ~ ➜ k get po
NAME READY STATUS RESTARTS AGE
webapp 1/1 Running 0 4m54s
controlplane ~ ➜ k get po webapp -o yaml > webapp.yml
controlplane ~ ➜ ls -l
total 4
-rw-rw-rw- 1 root root 0 Dec 13 05:39 sample.yaml
-rw-r--r-- 1 root root 2658 Dec 30 06:56 webapp.yml
controlplane ~ ➜ k delete po webapp $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "webapp" force deleted
controlplane ~ ➜ k get po
No resources found in default namespace.Add the volume and volumemount in the YAML file. Follow K8S docs.
## webapp.yml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: "2023-12-30T11:51:34Z"
name: webapp
namespace: default
resourceVersion: "506"
uid: 45b2b932-fbe3-4106-8926-55425cc05627
spec:
containers:
- env:
- name: LOG_HANDLERS
value: file
image: kodekloud/event-simulator
imagePullPolicy: Always
name: event-simulator
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: kube-api-access-77kjm
readOnly: true
- mountPath: /log
name: log-volume
volumes:
- name: log-volume
hostPath:
path: /var/log/webapp # directory location on host
type: Directory # this field is optionalcontrolplane ~ ➜ k apply -f webapp.yml
pod/webapp created
controlplane ~ ➜ k get po
NAME READY STATUS RESTARTS AGE
webapp 1/1 Running 0 3s -
-
Create a Persistent Volume with the given specification.
-
Volume Name: pv-log
-
Storage: 100Mi
-
Access Modes: ReadWriteMany
-
Host Path: /pv/log
-
Reclaim Policy: Retain
Answer
## pv-log.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
name: pv-log
spec:
persistentVolumeReclaimPolicy: Retain
accessModes:
- ReadWriteMany
capacity:
storage: 100Mi
storageClassName: ""
hostPath:
path: /pv/logcontrolplane ~ ➜ k apply -f pv-log.yaml
persistentvolume/pv-log created
controlplane ~ ➜ k get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pv-log 100Mi RWX Retain Available 2s -
-
Create a Persistent Volume Claim with the given specification.
-
Volume Name: claim-log-1
-
Storage Request: 50Mi
-
Access Modes: ReadWriteMany
Answer
## pvc-log.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: claim-log-1
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 50Micontrolplane ~ ➜ k apply -f pvc-log.yaml
persistentvolumeclaim/claim-log-1 created
controlplane ~ ➜ k get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pv-log 100Mi RWX Retain Bound default/claim-log-1 4m9s
controlplane ~ ➜ k get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
claim-log-1 Bound pv-log 100Mi RWX 11s -
-
Update the webapp pod to use the persistent volume claim as its storage. Replace hostPath configured earlier with the newly created PersistentVolumeClaim.
controlplane ~ ➜ k get po
NAME READY STATUS RESTARTS AGE
webapp 1/1 Running 0 46m
controlplane ~ ➜ k get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pv-log 100Mi RWX Retain Bound default/claim-log-1 39m
controlplane ~ ➜ k get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
claim-log-1 Bound pv-log 100Mi RWX 35m 30mAnswer
controlplane ~ ➜ k get po webapp -o yaml > webapp.ymlJust need to modify the volume sectino:
## webapp.yml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: "2023-12-30T12:55:20Z"
name: webapp
namespace: default
resourceVersion: "978"
uid: b6aec6fb-3333-4d77-9b34-0747f5de564c
spec:
containers:
- env:
- name: LOG_HANDLERS
value: file
image: kodekloud/event-simulator
imagePullPolicy: Always
name: event-simulator
volumes:
- name: log-volume
persistentVolumeClaim:
claimName: claim-log-1controlplane ~ ✦2 ➜ k apply -f webapp.yml
pod/webapp created
controlplane ~ ✦2 ➜ k get po
NAME READY STATUS RESTARTS AGE
webapp 1/1 Running 0 2s -
What is the reclaim policy set on pv-log?
controlplane ~ ✦2 ➜ k get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pv-log 100Mi RWX Retain Bound default/claim-log-1 7m27sAnswer
controlplane ~ ✦2 ➜ k describe pv pv-log
Name: pv-log
Labels: <none>
Annotations: pv.kubernetes.io/bound-by-controller: yes
Finalizers: [kubernetes.io/pv-protection]
StorageClass:
Status: Bound
Claim: default/claim-log-1
Reclaim Policy: Retain -
How many storage classes are there in the cluster?
Answer
controlplane ~ ➜ k get sc
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
local-path (default) rancher.io/local-path Delete WaitForFirstConsumer false 9m2s -
What is the Volume Binding Mode used for this storage class local-storage?
controlplane ~ ➜ k get sc
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
local-path (default) rancher.io/local-path Delete WaitForFirstConsumer false 9m44s
local-storage kubernetes.io/no-provisioner Delete WaitForFirstConsumer false 36s
portworx-io-priority-high kubernetes.io/portworx-volume Delete Immediate false 36sAnswer
controlplane ~ ✖ k describe sc local-storage
Name: local-storage
IsDefaultClass: No
Annotations: kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"storage.k8s.io/v1","kind":"StorageClass","metadata":{"annotations":{},"name":"local-storage"},"provisioner":"kubernetes.io/no-provisioner","volumeBindingMode":"WaitForFirstConsumer"}
Provisioner: kubernetes.io/no-provisioner
Parameters: <none>
AllowVolumeExpansion: <unset>
MountOptions: <none>
ReclaimPolicy: Delete
VolumeBindingMode: WaitForFirstConsumer
Events: <none> -
Create a new PersistentVolumeClaim by the name of local-pvc that should bind to the volume local-pv.
-
PVC: local-pvc
-
Correct Access Mode?
-
Correct StorageClass Used?
-
PVC requests volume size = 500Mi?
Answer
controlplane ~ ➜ k get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
local-pv 500Mi RWO Retain Available local-storage 19m
controlplane ~ ➜ k describe pv local-pv
Name: local-pv
Labels: <none>
Annotations: <none>
Finalizers: [kubernetes.io/pv-protection]
StorageClass: local-storage
Status: Available
Claim:
Reclaim Policy: Retain
Access Modes: RWO
VolumeMode: Filesystem
Capacity: 500Mi
Node Affinity:
Required Terms:
Term 0: kubernetes.io/hostname in [controlplane]
Message:
Source:
Type: LocalVolume (a persistent volume backed by local storage on a node)
Path: /opt/vol1
Events: <none>## local-pvc.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: local-pvc
spec:
accessModes:
- ReadWriteOnce
volumeMode: Filesystem
storageClassName: local-storage
resources:
requests:
storage: 500Micontrolplane ~ ➜ k apply -f local-pvc.yaml
persistentvolumeclaim/local-pvc created -
-
Create a new pod called nginx with the image nginx:alpine. The Pod should make use of the PVC local-pvc and mount the volume at the path /var/www/html. The PV local-pv should be in a bound state.
controlplane ~ ➜ k get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
local-pv 500Mi RWO Retain Available local-storage 29m
controlplane ~ ➜ k get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
local-pvc Pending local-storage 5m17sAnswer
controlplane ~ ➜ k run nginx --image nginx:alpine $do > nginx.yaml## nginx.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: nginx
name: nginx
spec:
containers:
- image: nginx:alpine
name: nginx
resources: {}
volumeMounts:
- mountPath: "/var/www/html"
name: local-pv
volumes:
- name: local-pv
persistentVolumeClaim:
claimName: local-pvc
status: {}controlplane ~ ➜ k apply -f nginx.yaml
pod/nginx created
controlplane ~ ➜ k get po
NAME READY STATUS RESTARTS AGE
nginx 1/1 Running 0 6s
controlplane ~ ➜ k get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
local-pv 500Mi RWO Retain Bound default/local-pvc local-storage 31m
controlplane ~ ➜ k get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
local-pvc Bound local-pv 500Mi RWO local-storage 7m16s -
Create a new Storage Class called delayed-volume-sc that makes use of the below specs:
-
provisioner: kubernetes.io/no-provisioner
-
volumeBindingMode: WaitForFirstConsumer
Answer
## delayed-volume-sc.yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: delayed-volume-sc
annotations:
storageclass.kubernetes.io/is-default-class: "false"
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumercontrolplane ~ ➜ k apply -f delayed-volume-sc.yaml
storageclass.storage.k8s.io/delayed-volume-sc created
controlplane ~ ➜ k get sc
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
local-path (default) rancher.io/local-path Delete WaitForFirstConsumer false 45m
local-storage kubernetes.io/no-provisioner Delete WaitForFirstConsumer false 35m
portworx-io-priority-high kubernetes.io/portworx-volume Delete Immediate false 35m
delayed-volume-sc kubernetes.io/no-provisioner Delete WaitForFirstConsumer false 3s -