This CKS practice question tests your understanding of system hardening. 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.
An administrator runs 'kubectl run test-pod --image=nginx --dry-run=client -o yaml > pod.yaml', then adds 'hostPID: true' and 'hostNetwork: true' to the pod's spec. After applying with 'kubectl apply -f pod.yaml', the pod is created but immediately goes into 'CrashLoopBackOff'. What is the likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "immediately / without restart"
Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The namespace has a PodSecurity enforce level that restricts hostPID and hostNetwork
The pod violates the Pod Security Standard of the namespace. If the namespace has an enforce label set to 'baseline' or 'restricted', it would block hostPID/hostNetwork unless the pod is exempted. Option A is correct because the PodSecurity admission plugin would deny the pod or at least warn. Option B is less likely as OOMKilled would show a different status. Option C is not a known issue. Option D is plausible but not the most direct cause given the scenario.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 container is missing a memory limit and gets OOMKilled
Why it's wrong here
OOMKilled would show OOMKilled status, not necessarily CrashLoopBackOff.
✓
The namespace has a PodSecurity enforce level that restricts hostPID and hostNetwork
Why this is correct
HostPID and hostNetwork are restricted in baseline and restricted levels, causing the pod to be rejected or crash.
Clue confirmation
The clue word "immediately / without restart" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The 'hostPID' and 'hostNetwork' fields cannot be combined
Why it's wrong here
They can be combined; no technical restriction.
✗
The pod lacks the necessary Linux capabilities
Why it's wrong here
hostPID/hostNetwork do not require additional capabilities beyond what's default.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Trap categories for this question
Command / output trap
OOMKilled would show OOMKilled status, not necessarily CrashLoopBackOff.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CKS ACL questions on filtering logic and placement.
System Hardening — This question tests System Hardening — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The namespace has a PodSecurity enforce level that restricts hostPID and hostNetwork — The pod violates the Pod Security Standard of the namespace. If the namespace has an enforce label set to 'baseline' or 'restricted', it would block hostPID/hostNetwork unless the pod is exempted. Option A is correct because the PodSecurity admission plugin would deny the pod or at least warn. Option B is less likely as OOMKilled would show a different status. Option C is not a known issue. Option D is plausible but not the most direct cause given the scenario.
What should I do if I get this CKS question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CKS ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
What is the key concept behind this question?
Standard ACLs match source addresses.
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