- A
The nginx worker_connections setting is too high.
High worker_connections can cause each worker to allocate large amounts of memory for connection pools, leading to memory exhaustion and high CPU usage as workers compete for resources.
- B
The vm.swappiness value is set to 100.
Why wrong: A high swappiness value makes the kernel more aggressive in swapping, but the symptoms of low memory and high CPU are not directly caused by swappiness alone.
- C
The net.core.somaxconn setting is too low.
Why wrong: somaxconn limits the listen backlog, which can cause connection refused under high load, but does not directly cause high memory and CPU usage by workers.
- D
The kernel parameter kernel.pid_max is set too low.
Why wrong: The pid_max parameter limits the number of processes, not memory or CPU usage. A low pid_max could prevent new processes from starting, but the symptoms here are about existing workers consuming resources.
Quick Answer
The answer is that an excessively high `worker_connections` setting is the most likely cause. When this directive is set too high, each Nginx worker process attempts to juggle far more concurrent connections than the system’s 4 CPU cores and 8 GB of RAM can handle, leading to CPU saturation as processes fight for processing time and memory exhaustion as each connection consumes a socket buffer. On the LFCS exam, this scenario tests your understanding of Nginx’s event-driven architecture and resource limits—a common trap is confusing `worker_connections` with `worker_processes`, but remember that even a single worker with too many connections can overwhelm available memory and CPU. The key symptom here is that the server is intermittently unresponsive, not completely crashed, which points to resource contention rather than a hard limit. Memory tip: think of `worker_connections` as a “guest list” per worker—if you invite 10,000 guests to a party with only 8 GB of punch, everyone gets a sip but nobody gets a full cup.
LFCS Operation of Running Systems Practice Question
This LFCS practice question tests your understanding of operation of running systems. 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 systems administrator receives reports that a web server running Nginx is intermittently unresponsive. The server has 8 GB of RAM and 4 CPU cores. The administrator runs 'free -m' and sees that available memory is low, and 'top' shows that several nginx worker processes are using a high percentage of CPU. Which of the following is the most likely cause of the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The nginx worker_connections setting is too high.
The correct answer is A. When `worker_connections` is set too high, each Nginx worker process attempts to handle more concurrent connections than the system can support, leading to CPU saturation and memory exhaustion. This matches the symptoms of high CPU usage by worker processes and low available memory, causing intermittent unresponsiveness.
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.
- ✓
The nginx worker_connections setting is too high.
Why this is correct
High worker_connections can cause each worker to allocate large amounts of memory for connection pools, leading to memory exhaustion and high CPU usage as workers compete for resources.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The vm.swappiness value is set to 100.
Why it's wrong here
A high swappiness value makes the kernel more aggressive in swapping, but the symptoms of low memory and high CPU are not directly caused by swappiness alone.
- ✗
The net.core.somaxconn setting is too low.
Why it's wrong here
somaxconn limits the listen backlog, which can cause connection refused under high load, but does not directly cause high memory and CPU usage by workers.
- ✗
The kernel parameter kernel.pid_max is set too low.
Why it's wrong here
The pid_max parameter limits the number of processes, not memory or CPU usage. A low pid_max could prevent new processes from starting, but the symptoms here are about existing workers consuming resources.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse `worker_connections` with `net.core.somaxconn`, assuming a backlog limit causes CPU issues, but `worker_connections` directly impacts per-worker resource consumption under load.
Detailed technical explanation
How to think about this question
Nginx uses an event-driven, asynchronous architecture where each worker process handles multiple connections via epoll (Linux) or kqueue (BSD). The `worker_connections` directive defines the maximum number of simultaneous connections per worker; exceeding this limit forces the worker to context-switch excessively, leading to CPU thrashing. In practice, a common misconfiguration is setting `worker_connections` to 4096 or higher on a system with limited RAM, causing each worker to allocate large connection pools that exhaust memory and CPU.
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 LFCS 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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Operation of Running Systems — study guide chapter
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FAQ
Questions learners often ask
What does this LFCS question test?
Operation of Running Systems — This question tests Operation of Running Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The nginx worker_connections setting is too high. — The correct answer is A. When `worker_connections` is set too high, each Nginx worker process attempts to handle more concurrent connections than the system can support, leading to CPU saturation and memory exhaustion. This matches the symptoms of high CPU usage by worker processes and low available memory, causing intermittent unresponsiveness.
What should I do if I get this LFCS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 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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