This LFCS practice question tests your understanding of service configuration. 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 system administrator wants to limit the CPU usage of a service. Which systemd resource control directive should be used?
CPUShares
Why wrong: Controls relative weight, not absolute limit.
CPUQuota
Why wrong: Alone it is ignored; CPUAccounting must be enabled.
CPUAccounting=yes and CPUQuota
CPUAccounting enables accounting, then CPUQuota can be applied.
CPULimit
Why wrong: Not a valid systemd directive.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
CPUAccounting=yes and CPUQuota
Option C is correct because to limit CPU usage in systemd, you must first enable CPU accounting with `CPUAccounting=yes` to track CPU consumption, and then set `CPUQuota` to specify a maximum percentage of CPU time the service can use. Without `CPUAccounting=yes`, the `CPUQuota` directive is ignored by systemd, making the combination essential for enforcing a hard CPU limit.
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.
CPUShares
Why it's wrong here
Controls relative weight, not absolute limit.
CPUQuota
Why it's wrong here
Alone it is ignored; CPUAccounting must be enabled.
CPUAccounting=yes and CPUQuota
Why this is correct
CPUAccounting enables accounting, then CPUQuota can be applied.
Related concept
Read the scenario before looking for a memorised answer.
CPULimit
Why it's wrong here
Not a valid systemd directive.
Common exam traps
The trap here is that candidates assume `CPUQuota` works independently, but the LFCS exam tests the requirement to enable `CPUAccounting=yes` first, as systemd defaults to accounting being off for performance reasons.
Detailed technical explanation
Under the hood, `CPUQuota` is implemented via the Linux cgroups v1 `cpu.cfs_quota_us` and `cpu.cfs_period_us` files, where the quota is expressed as a percentage of a single CPU core (e.g., `CPUQuota=50%` limits the service to half a core). A subtle behavior is that `CPUQuota` can be set to a value greater than 100% to allow a service to use multiple cores, but the quota is still a hard cap on total CPU time across all cores. In real-world scenarios, this is critical for preventing a misbehaving service from starving other processes, such as limiting a web server to 200% of a CPU to ensure it doesn't monopolize a dual-core system.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
Service Configuration — This question tests Service Configuration — Read the scenario before looking for a memorised answer..
The correct answer is: CPUAccounting=yes and CPUQuota — Option C is correct because to limit CPU usage in systemd, you must first enable CPU accounting with `CPUAccounting=yes` to track CPU consumption, and then set `CPUQuota` to specify a maximum percentage of CPU time the service can use. Without `CPUAccounting=yes`, the `CPUQuota` directive is ignored by systemd, making the combination essential for enforcing a hard CPU limit.
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
This LFCS practice question is part of Courseiva's free Linux Foundation certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LFCS exam.
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