This KCNA practice question tests your understanding of kubernetes fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
A developer wants to inject environment variables into a pod from a ConfigMap named 'app-config'. Which YAML snippet correctly mounts all key-value pairs from the ConfigMap as environment variables?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
envFrom:
- configMapRef:
name: app-config
Option B is correct because `envFrom` with a `configMapRef` injects all key-value pairs from the ConfigMap named 'app-config' as environment variables into the container. This is the standard Kubernetes method for bulk injection of ConfigMap data into environment variables, as opposed to selecting individual keys.
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.
✗
env:
- name: CONFIG
value: "$(CONFIGMAP)"
Why it's wrong here
This is not a valid way to reference a ConfigMap.
✓
envFrom:
- configMapRef:
name: app-config
Why this is correct
This mounts all keys from the ConfigMap as environment variables.
Related concept
Read the scenario before looking for a memorised answer.
This mounts a single key as an environment variable.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse `envFrom` (bulk injection) with `env` + `configMapKeyRef` (single key injection) or volume mounts (file-based injection), leading them to pick options that inject only one key or mount files instead of environment variables.
Detailed technical explanation
How to think about this question
Under the hood, `envFrom` with `configMapRef` iterates over all entries in the ConfigMap and creates an environment variable for each key, with the value set to the corresponding value. If a key is not a valid environment variable name (e.g., contains hyphens), Kubernetes will skip it silently, which can lead to missing variables in production — a subtle behavior to watch for. In real-world scenarios, this is commonly used for injecting configuration like database URLs or feature flags without hardcoding them in the pod spec.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this KCNA question in full detail.
Kubernetes Fundamentals — This question tests Kubernetes Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: envFrom:
- configMapRef:
name: app-config — Option B is correct because `envFrom` with a `configMapRef` injects all key-value pairs from the ConfigMap named 'app-config' as environment variables into the container. This is the standard Kubernetes method for bulk injection of ConfigMap data into environment variables, as opposed to selecting individual keys.
What should I do if I get this KCNA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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