State Persistence

Question 1

What is a persistent volume?

Answer 1

A PersistentVolume (PV) is a piece of storage in the cluster. It is a resource in the cluster just like a node is a cluster resource. PVs have a lifecycle independent of any individual Pod that uses the PV.

Question 2

How does a Persistent Volume differ from a Volume?

Answer 2

A persistent volume is a subset of Volumes, where data can be persisted beyond the lifecycle of a Pod that uses it. Volumes are often ephemeral and are created as a Pod is started and deleted with the Pod.

Question 3

In a Pod definition, how is a volume created from a Directory on the host node? (e.g. a directory on the host node at a path of /data)

Answer 3

spec: volumes: - name: data-volume hostPath: path: /data type: Directory

Question 4

In a Pod definition, how is a volume applied to a container?

Answer 4

spec: containers: - volumeMounts: - mountPath: /opt name: data-volume

Question 5

What is a hostPath volume type?

Answer 5

A hostPath volume mounts a file or directory from the host node’s filesystem into your Pod.

Question 6

What are some issues with the hostPath volume type?

Answer 6

The volume on each node is different, and is not synchronised between nodes. The files or directories created on the underlying hosts are only writable by root. You either need to run your process as root in a privileged Container or modify the file permissions on the host to be able to write to a hostPath volume

Question 7

What is an emptyDir volume type?

Answer 7

An emptyDir volume is first created when a Pod is assigned to a node, and exists as long as that Pod is running on that node. As the name says, the emptyDir volume is initially empty. All containers in the Pod can read and write the same files in the emptyDir volume, though that volume can be mounted at the same or different paths in each container. When a Pod is removed from a node for any reason, the data in the emptyDir is deleted permanently.

Question 8

In a Pod definition, configure an emptyDir volume.

e.g. to /cache path of a container named test-container

Answer 8

spec: containers: - name: test-container volumeMounts: - mountPath: /cache name: empty-volume volumes: - name: empty-volume emptyDir: {}

Question 9

In a Pod definition, how is a volume created from AWS Elastic Block Store (EBS)? (e.g. AWS EBS with ID of myAWSEBSID, and a file system type of ext4)

Answer 9

spec: volumes: - name: data-volume awsElasticBlockStore: volumeID: myAWSEBSID fsType: ext4

Question 10

What is the apiVersion of a Persistent Volume?

Answer 10

v1

Question 11

What are the three types of Access Mode for a Persistent Volume?

Answer 11

• ReadOnlyMany
• ReadWriteOnce
• ReadWriteMany

Question 12

In a PersistentVolume definition, how can a read-only volume be created from a directory in the host? (e.g. 1Gi at a path of /tmp/foo)

Answer 12

spec: accessModes: - ReadWriteOnce capacity: storage: 1Gi hostPath: path: /tmp/foo

Question 13

How can a Persistent Volume be associated with a Pod

Answer 13

With a Persistent Volume Claim

Question 14

What is the imperative command to list all Persistent Volumes?

Answer 14

kubectl get pv

Question 15

What considerations does Kubernetes take into account when binding a Persistent Volume Claim to a Persistent Volume?

Answer 15

• sufficient storage capacity
• access modes
• volume modes
• storage class

Question 16

If no volumes are available, what is the state of any further Persistent Volume Claims?

Answer 16

Pending state

Question 17

What is the apiVersion of Persistent Volume Claim

Answer 17

v1

Question 18

In Persistent Volume Claim definition, how can a read-only volume be bound? (e.g. 500Mi storage)

Answer 18

spec: accessModes: - ReadWriteOnce resources: requests: storage: 500Mi

Question 19

What is the imperative command to list all Persistent Volume Claims?

Answer 19

kubectl get pvc

Question 20

In Pod definition, how is a Persistent Volume Claim associated with a container? (e.g. a PVC named my-pvc, mounted at /var/www)

Answer 20

spec: containers: - volumemounts: - mountPath: "/var/www" name: myVolume volumes: - name: myVolume persistentVolumeClaim: claimName: my-pvc