PersistentVolumeClaim (PVC) definition in Kubernetes - Mini Project: Build & Apply

Create a PersistentVolumeClaim (PVC) in Kubernetes

📖 Scenario: You are setting up storage for a Kubernetes application. You need to create a PersistentVolumeClaim (PVC) to request storage from the cluster.

🎯 Goal: Learn how to write a YAML definition for a PersistentVolumeClaim (PVC) that requests storage with specific size and access mode.

📋 What You'll Learn

Create a YAML dictionary with apiVersion, kind, metadata, and spec fields

Set apiVersion to v1

Set kind to PersistentVolumeClaim

Add metadata with a name my-pvc

In spec, set accessModes to ReadWriteOnce

In spec, set resources.requests.storage to 1Gi

💡 Why This Matters

🌍 Real World

Kubernetes applications often need persistent storage to save data beyond the life of a pod. PVCs let you request this storage easily.

💼 Career

Understanding PVCs is essential for Kubernetes administrators and DevOps engineers to manage stateful applications and storage resources.

1

Create the basic PVC structure

Create a YAML dictionary with apiVersion set to v1, kind set to PersistentVolumeClaim, and metadata with name set to my-pvc.

Kubernetes

# Your code here

Hint

Start by defining the top-level keys and the metadata name.

2

Add access mode to the spec

Add a spec section with accessModes set to a list containing ReadWriteOnce.

Kubernetes

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
# Add spec with accessModes below
# Your code here

Hint

Remember that accessModes is a list under spec.

3

Add storage request to the spec

Under spec, add resources.requests.storage set to 1Gi to request 1 gigabyte of storage.

Kubernetes

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
    - ReadWriteOnce
# Add resources.requests.storage: 1Gi below
# Your code here

Hint

Indent resources, then requests, then set storage to 1Gi.

4

Display the complete PVC YAML

Print the complete YAML definition of the PersistentVolumeClaim.

Kubernetes

# Print the PVC YAML below
# Your code here

Hint

Show the full YAML content as the final output.

Practice

1. What is the main purpose of a PersistentVolumeClaim (PVC) in Kubernetes?

easy

A. To configure network policies

B. To define a container image for a pod

C. To schedule pods on specific nodes

D. To request storage resources from the cluster

Solution

1. Step 1: Understand PVC role

   A PVC is used to request storage resources in Kubernetes, separating storage use from storage details.

2. Step 2: Compare options

   Options A, B, and D relate to other Kubernetes features, not storage requests.

3. Final Answer:

   To request storage resources from the cluster -> Option D

4. Quick Check:

   PVC = Storage request [OK]

Hint: PVC always requests storage, not images or network [OK]

Common Mistakes:

• Confusing PVC with Pod or Deployment definitions
• Thinking PVC schedules pods
• Mixing PVC with network policies

2. Which of the following is the correct minimal YAML snippet to define a PVC requesting 5Gi of storage with ReadWriteOnce access mode?

easy

A. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-pvc
spec:
accessModes:
- ReadOnlyMany
resources:
requests:
storage: 5Gi

B. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 5Gi

C. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-pvc
spec:
accessModes:
- ReadWriteMany
resources:
limits:
storage: 5Gi

D. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
cpu: 5Gi

Solution

1. Step 1: Check accessModes and storage request

   apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 5Gi correctly uses ReadWriteOnce and requests 5Gi storage under resources.requests.

2. Step 2: Identify errors in other options

   apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadOnlyMany resources: requests: storage: 5Gi uses ReadOnlyMany (not requested). apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteMany resources: limits: storage: 5Gi uses limits instead of requests. apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteOnce resources: requests: cpu: 5Gi incorrectly requests cpu instead of storage.

3. Final Answer:

   Correct minimal PVC YAML with 5Gi and ReadWriteOnce -> Option B

4. Quick Check:

   accessModes + storage request = apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 5Gi [OK]

Hint: Use resources.requests.storage for size, accessModes for access [OK]

Common Mistakes:

• Using limits instead of requests for storage
• Wrong accessModes value
• Requesting cpu instead of storage

3. Given this PVC YAML snippet, what will be the requested storage size and access mode?

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: data-pvc
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 10Gi
  storageClassName: fast-storage

medium

A. 10Gi storage with ReadWriteMany access

B. 10Gi storage with ReadWriteOnce access

C. 5Gi storage with ReadWriteMany access

D. 10Gi storage with ReadOnlyMany access

Solution

1. Step 1: Read storage size

   The YAML requests 10Gi storage under resources.requests.storage.

2. Step 2: Read access mode

   Access mode is ReadWriteMany as specified under accessModes.

3. Final Answer:

   10Gi storage with ReadWriteMany access -> Option A

4. Quick Check:

   storage=10Gi, access=ReadWriteMany [OK]

Hint: Check resources.requests.storage and accessModes list [OK]

Common Mistakes:

• Confusing ReadWriteOnce with ReadWriteMany
• Misreading storage size
• Ignoring storageClassName as it doesn't affect size or access

4. Identify the error in this PVC YAML snippet:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: test-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 2GB

medium

A. metadata name is missing

B. accessModes should be ReadOnlyMany

C. storage size unit should be Gi, not GB

D. apiVersion should be apps/v1

Solution

1. Step 1: Check storage size unit

   Kubernetes expects storage size units like Gi, Mi, not GB. '2GB' is invalid.

2. Step 2: Verify other fields

   accessModes and metadata name are correct. apiVersion for PVC is v1, not apps/v1.

3. Final Answer:

   storage size unit should be Gi, not GB -> Option C

4. Quick Check:

   Use Gi for storage size units [OK]

Hint: Use Gi, Mi units for storage size, not GB [OK]

Common Mistakes:

• Using GB instead of Gi for storage size
• Wrong apiVersion for PVC
• Changing accessModes unnecessarily

5. You want to create a PVC that requests 20Gi storage with ReadWriteOnce access and uses a storage class named "premium-ssd". Which YAML snippet correctly defines this PVC?

hard

A. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: premium-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 20Gi
storageClassName: premium-ssd

B. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: premium-pvc
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 20Gi
storageClassName: premium-ssd

C. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: premium-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
limits:
storage: 20Gi
storageClassName: premium-ssd

D. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: premium-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 20GB
storageClassName: premium-ssd

Solution

1. Step 1: Verify accessModes and storage size

   apiVersion: v1 kind: PersistentVolumeClaim metadata: name: premium-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 20Gi storageClassName: premium-ssd uses ReadWriteOnce and requests 20Gi storage correctly.

2. Step 2: Check storageClassName and units

   apiVersion: v1 kind: PersistentVolumeClaim metadata: name: premium-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 20Gi storageClassName: premium-ssd correctly sets storageClassName to premium-ssd and uses Gi units. Other options have wrong accessModes, use limits instead of requests, or wrong units (GB).

3. Final Answer:

   Correct PVC with 20Gi, ReadWriteOnce, and premium-ssd storage class -> Option A

4. Quick Check:

   accessModes=ReadWriteOnce + requests.storage=20Gi + storageClassName= premium-ssd [OK]

Hint: Use requests.storage with Gi units and correct accessModes [OK]

Common Mistakes:

• Using limits instead of requests for storage
• Wrong accessModes value
• Using GB instead of Gi for storage size