mediumMultiple Choice
CV0-004 Practice Question: Deploying a containerized application using…
A company is deploying a containerized application using Kubernetes on a public cloud. The development team has created a Docker image and pushed it to a private container registry. The deployment YAML points to the registry. However, when the deployment is applied, the pods fail to start with an 'ImagePullBackOff' error. The cloud administrator verifies that the registry is reachable from the cluster nodes and that the image exists. What is the most likely reason for the failure?
⚠ Common exam trap
CompTIA often tests the distinction between image existence and registry authentication, trapping candidates who assume that because the image is present and the registry is reachable, the pull should succeed without considering the need for explicit credentials.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The deployment lacks a secret for registry authentication.
The most likely reason for the ImagePullBackOff error is that the deployment lacks a Kubernetes secret for registry authentication. Since the image is stored in a private container registry, the kubelet must authenticate with the registry to pull the image. Without a properly configured imagePullSecret in the pod spec, the kubelet cannot obtain credentials, resulting in a failed pull and the ImagePullBackOff status.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The deployment lacks a secret for registry authentication.
Why this is correct
The private registry requires authentication, and Kubernetes pulls images using credentials supplied via an imagePullSecret referenced in the pod spec. Without that secret, the kubelet receives an authorisation denial from the registry, producing ImagePullBackOff despite the image existing and the registry being reachable.
- ✗
The cluster nodes are out of disk space.
Why it's wrong here
Disk pressure triggers DiskPressure eviction and node taints, producing Pending or Evicted pods rather than a registry pull failure. Insufficient node storage is the culprit when the kubelet cannot write image layers locally, not when authentication to a private registry is rejected.
- ✗
The image tag is incorrect.
Why it's wrong here
An incorrect tag yields manifest-unknown or not-found errors, but the stem confirms the image exists in the registry, so the reference resolves. Tag mismatches are the classic cause when the image genuinely is absent, which the administrator has already ruled out.
- ✗
The pod does not have sufficient CPU resources.
Why it's wrong here
CPU issues cause OOMKilled, not ImagePullBackOff.
Go deeper
Related to this question
About these practice questions
One of 834 original CV0-004 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CV0-004 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CV0-004 exam.