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.
A security requirement states that a container must run with a read-only root filesystem. Which field must be set in the container's securityContext?
runAsUser: 1000
Why wrong: This sets the user ID but does not affect filesystem write permissions.
capabilities: drop: ["ALL"]
Why wrong: This drops all capabilities but does not make the filesystem read-only.
allowPrivilegeEscalation: false
Why wrong: This prevents privilege escalation but does not make the filesystem read-only.
readOnlyRootFilesystem: true
This makes the container's root filesystem read-only.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
readOnlyRootFilesystem: true
Setting `readOnlyRootFilesystem: true` in the container's `securityContext` enforces that the container's root filesystem is mounted as read-only, preventing any writes to the filesystem at the root level. This satisfies the security requirement by ensuring that even if a process is compromised, it cannot modify system binaries, configuration files, or other critical files within the container's root filesystem.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
runAsUser: 1000
Why it's wrong here
This sets the user ID but does not affect filesystem write permissions.
capabilities: drop: ["ALL"]
Why it's wrong here
This drops all capabilities but does not make the filesystem read-only.
allowPrivilegeEscalation: false
Why it's wrong here
This prevents privilege escalation but does not make the filesystem read-only.
readOnlyRootFilesystem: true
Why this is correct
This makes the container's root filesystem read-only.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse security context fields that control process privileges (like `runAsUser` or `capabilities`) with filesystem mount restrictions, mistakenly thinking dropping capabilities or disabling privilege escalation will make the filesystem read-only.
Detailed technical explanation
When `readOnlyRootFilesystem: true` is set, Kubernetes configures the container's root filesystem as a read-only mount using the `overlay2` or `aufs` storage driver, while still allowing writes to ephemeral volumes (e.g., `emptyDir`) and `tmpfs` mounts for temporary data. This is enforced at the kernel level via the `MS_RDONLY` mount flag, meaning even root inside the container cannot write to the root filesystem unless a writable volume is explicitly mounted. In real-world scenarios, this is critical for compliance with security standards like PCI-DSS or CIS benchmarks, where immutable infrastructure requires that containers cannot persist unauthorized changes.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
What to study next
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FAQ
Application Environment, Configuration and Security — This question tests Application Environment, Configuration and Security — Read the scenario before looking for a memorised answer..
The correct answer is: readOnlyRootFilesystem: true — Setting `readOnlyRootFilesystem: true` in the container's `securityContext` enforces that the container's root filesystem is mounted as read-only, preventing any writes to the filesystem at the root level. This satisfies the security requirement by ensuring that even if a process is compromised, it cannot modify system binaries, configuration files, or other critical files within the container's root filesystem.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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