The answer is to add `runAsUser: 999` to the container's securityContext. This is correct because the official PostgreSQL image is built to run as the 'postgres' user with UID 999 by default, and setting `runAsUser: 999` explicitly overrides the container’s runtime user to that non-root UID, satisfying the `runAsNonRoot: true` constraint and resolving the "container has runAsNonRoot and image will run as root" error. On the CKAD exam, this scenario tests your understanding of Pod security contexts and how `runAsNonRoot` works as a validation gate—it only blocks root, but does not automatically set a user; you must pair it with a specific `runAsUser` that matches the image’s intended user. A common trap is assuming `runAsNonRoot: true` alone fixes the issue, or picking an arbitrary UID like 1000 that may not exist in the container image. Memory tip: "NonRoot needs a UID—match the image’s default, like postgres at 999."
CKAD Practice Question: Application Environment, Configuration and Security
This CKAD practice question tests your understanding of application environment, configuration and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are a Kubernetes administrator responsible for a production cluster. A development team has deployed a Pod named 'app-pod' that runs a container with a PostgreSQL database. The team reports that the Pod is failing to start with an error: 'Error: container has runAsNonRoot and image will run as root (runtime error)'. The Pod YAML is as follows:
```yaml
apiVersion: v1
kind: Pod
metadata:
name: app-pod
spec:
containers:
- name: db
image: postgres:latest
securityContext:
runAsNonRoot: true
```
The team wants to ensure the container runs securely without running as root. What is the BEST course of action?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add `runAsUser: 999` to the container's securityContext to run the container as the postgres user.
Option A is correct because the PostgreSQL official image runs as the 'postgres' user with UID 999 by default. Adding `runAsUser: 999` to the container's securityContext overrides the user to a non-root UID, satisfying the `runAsNonRoot: true` constraint and allowing the container to start without the runtime error.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Add `runAsUser: 999` to the container's securityContext to run the container as the postgres user.
Why this is correct
This explicitly sets the user to a non-root user, satisfying runAsNonRoot.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Remove `runAsNonRoot: true` from the securityContext to allow the container to run as root.
Why it's wrong here
This would run the container as root, which is insecure and not recommended.
✗
Increase the Pod's resource limits because the error is due to insufficient memory.
Why it's wrong here
The error is about security context, not resources.
✗
Create a PodSecurityPolicy that allows running as root.
Why it's wrong here
This is a cluster-wide change and not the best immediate fix for this single Pod.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think removing `runAsNonRoot` is the simplest fix, but the question explicitly requires the container to run securely without root, so the correct action is to specify a non-root user ID rather than disabling the security constraint.
Detailed technical explanation
How to think about this question
The `runAsNonRoot: true` security context setting tells the container runtime (e.g., containerd) to verify that the container's user ID is not 0 (root). The PostgreSQL image's default user is UID 999, but without explicitly setting `runAsUser: 999`, the runtime may still see the image's entrypoint as root if the image does not define a USER directive. Setting `runAsUser: 999` explicitly ensures the container runs as the postgres user, bypassing the root check. In real-world scenarios, this is common when using images that expect a specific non-root user but do not enforce it in the Dockerfile.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the CKAD exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKAD question in full detail.
Application Environment, Configuration and Security — This question tests Application Environment, Configuration and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add `runAsUser: 999` to the container's securityContext to run the container as the postgres user. — Option A is correct because the PostgreSQL official image runs as the 'postgres' user with UID 999 by default. Adding `runAsUser: 999` to the container's securityContext overrides the user to a non-root UID, satisfying the `runAsNonRoot: true` constraint and allowing the container to start without the runtime error.
What should I do if I get this CKAD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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