This CKS practice question tests your understanding of system hardening. 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.
Which Linux capability must be added to a container to allow it to change the system time (e.g., using the 'date' command)?
Why wrong: CAP_SYS_NICE allows setting nice values and changing scheduling priority, not time.
B
CAP_SYS_RESOURCE
Why wrong: CAP_SYS_RESOURCE is for overriding resource limits, not for changing the system time.
C
CAP_SYS_ADMIN
Why wrong: CAP_SYS_ADMIN is a broad capability that includes many privileges, but for changing time specifically, CAP_SYS_TIME is more appropriate and granular.
D
CAP_SYS_TIME
CAP_SYS_TIME allows setting the system clock and real-time clock.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
CAP_SYS_TIME
The `CAP_SYS_TIME` capability is specifically required for a container to modify the system clock, including using the `date` command to set the time. Without this capability, the container's process will receive an EPERM error when attempting to change the system time, as the kernel enforces this restriction at the system call level (e.g., `settimeofday`, `clock_settime`).
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.
✗
CAP_SYS_NICE
Why it's wrong here
CAP_SYS_NICE allows setting nice values and changing scheduling priority, not time.
✗
CAP_SYS_RESOURCE
Why it's wrong here
CAP_SYS_RESOURCE is for overriding resource limits, not for changing the system time.
✗
CAP_SYS_ADMIN
Why it's wrong here
CAP_SYS_ADMIN is a broad capability that includes many privileges, but for changing time specifically, CAP_SYS_TIME is more appropriate and granular.
✓
CAP_SYS_TIME
Why this is correct
CAP_SYS_TIME allows setting the system clock and real-time clock.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between `CAP_SYS_ADMIN` (a catch-all for many privileged operations) and `CAP_SYS_TIME` (the specific capability for clock manipulation), leading candidates to incorrectly select `CAP_SYS_ADMIN` because they assume it covers all system administration tasks.
Detailed technical explanation
How to think about this question
Under the hood, the Linux kernel checks for `CAP_SYS_TIME` in the `capable()` call within the `do_sys_settimeofday64()` and `do_clock_settime()` functions. In a real-world scenario, a containerized NTP client (e.g., `chronyd` or `ntpd`) requires `CAP_SYS_TIME` to adjust the clock, but it also needs `CAP_SYS_NICE` for scheduling and `CAP_NET_BIND_SERVICE` for binding to privileged ports; however, the time-setting permission is exclusively tied to `CAP_SYS_TIME`.
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 CKS 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 CKS question in full detail.
System Hardening — This question tests System Hardening — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: CAP_SYS_TIME — The `CAP_SYS_TIME` capability is specifically required for a container to modify the system clock, including using the `date` command to set the time. Without this capability, the container's process will receive an EPERM error when attempting to change the system time, as the kernel enforces this restriction at the system call level (e.g., `settimeofday`, `clock_settime`).
What should I do if I get this CKS 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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