- A
Set up a cron job to run every minute that checks memory usage with free and if > 90%, restart the service with systemctl restart. Also configure MemoryMax=32G in the systemd unit.
Why wrong: Cron is reactive, not real-time; restart may be disruptive and does not detect unresponsiveness.
- B
Configure sysctl vm.overcommit_memory=2 to prevent overcommit, and allocate huge pages for Java. Also set Restart=always in the systemd unit.
Why wrong: Does not limit memory directly; overcommit settings may cause new failures.
- C
Use ulimit -v 33554432 in the service script to limit virtual memory, and set Restart=always. Also configure a cron job to send alerts when dmesg shows OOM.
Why wrong: ulimit is per-process and not as effective as cgroup limit; lacks watchdog for unresponsiveness.
- D
Configure systemd service with WatchdogSec=30, Restart=on-failure, MemoryMax=32G. Also set up a log watcher that alerts when memory usage exceeds 28G via journalctl and a custom script.
Watchdog ensures restart if unresponsive, MemoryMax limits memory, log watcher provides early warning.
LFCS Operation of Running Systems Practice Question
This LFCS practice question tests your understanding of operation of running systems. 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.
An e-commerce company runs a critical application on a Linux server that occasionally becomes unresponsive. The server has 64GB RAM and runs a Java application. The operations team notices that during peak hours, the system becomes very slow and eventually the application crashes with 'OutOfMemoryError'. After restart, it works fine for a while. They suspect a memory leak but also want to ensure the system does not go down during peak hours. The system uses systemd to manage the Java service. The administrator needs to implement a solution that: (1) automatically restarts the service if it becomes unresponsive, (2) limits the memory usage of the service to prevent OOM kills on the system, and (3) provides early warning of high memory usage. Which of the following approaches best meets these requirements?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Configure systemd service with WatchdogSec=30, Restart=on-failure, MemoryMax=32G. Also set up a log watcher that alerts when memory usage exceeds 28G via journalctl and a custom script.
Option D is correct because it uses systemd's WatchdogSec to detect unresponsiveness and Restart=on-failure to automatically restart the service, while MemoryMax=32G enforces a hard memory limit via cgroups to prevent OOM kills. The custom log watcher provides early warning by alerting when memory usage exceeds 28G, satisfying all three requirements.
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.
- ✗
Set up a cron job to run every minute that checks memory usage with free and if > 90%, restart the service with systemctl restart. Also configure MemoryMax=32G in the systemd unit.
Why it's wrong here
Cron is reactive, not real-time; restart may be disruptive and does not detect unresponsiveness.
- ✗
Configure sysctl vm.overcommit_memory=2 to prevent overcommit, and allocate huge pages for Java. Also set Restart=always in the systemd unit.
Why it's wrong here
Does not limit memory directly; overcommit settings may cause new failures.
- ✗
Use ulimit -v 33554432 in the service script to limit virtual memory, and set Restart=always. Also configure a cron job to send alerts when dmesg shows OOM.
Why it's wrong here
ulimit is per-process and not as effective as cgroup limit; lacks watchdog for unresponsiveness.
- ✓
Configure systemd service with WatchdogSec=30, Restart=on-failure, MemoryMax=32G. Also set up a log watcher that alerts when memory usage exceeds 28G via journalctl and a custom script.
Why this is correct
Watchdog ensures restart if unresponsive, MemoryMax limits memory, log watcher provides early warning.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ulimit or sysctl settings with cgroup-based memory limits, or assume cron-based polling is sufficient for unresponsiveness detection, overlooking systemd's built-in WatchdogSec mechanism.
Detailed technical explanation
How to think about this question
systemd's WatchdogSec works by having the service send periodic 'ping' messages via sd_notify(0, "WATCHDOG=1"); if the service fails to notify within the interval, systemd considers it unresponsive and triggers the configured restart action. MemoryMax uses cgroup v2 memory.max to enforce a hard limit; when exceeded, the kernel invokes OOM killer within the cgroup, protecting the rest of the system. In production, combining WatchdogSec with a health check script that updates the watchdog status is common to detect application-level hangs beyond simple process liveness.
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: Configure systemd service with WatchdogSec=30, Restart=on-failure, MemoryMax=32G. Also set up a log watcher that alerts when memory usage exceeds 28G via journalctl and a custom script. — Option D is correct because it uses systemd's WatchdogSec to detect unresponsiveness and Restart=on-failure to automatically restart the service, while MemoryMax=32G enforces a hard memory limit via cgroups to prevent OOM kills. The custom log watcher provides early warning by alerting when memory usage exceeds 28G, satisfying all three requirements.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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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