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 is configuring a custom systemd service that runs a Python script. The script logs output to stdout. The administrator wants to ensure that the service restarts automatically if it crashes, but only after a 10-second delay. Which directive should be added to the [Service] section of the unit file?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Restart=on-failure
RestartSec=10
Option B is correct because `Restart=on-failure` ensures the service restarts only when it exits with a non-zero exit code or is terminated by a signal (e.g., SIGKILL), which matches the 'crashes' scenario. Adding `RestartSec=10` introduces a 10-second delay before the restart attempt, as required. The other options either restart on success (irrelevant) or always restart (which would restart even on intentional stops), or omit the restart condition entirely.
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.
✗
Restart=on-success
RestartSec=10
Why it's wrong here
Restarts on successful exit, not on failure.
✓
Restart=on-failure
RestartSec=10
Why this is correct
Restarts the service only when it exits with a non-zero exit code or is terminated by a signal, with a 10-second delay.
Related concept
Read the scenario before looking for a memorised answer.
✗
Restart=always
RestartSec=10
Why it's wrong here
Restarts always, even on successful exit, which may not be desired.
✗
RestartSec=10
Why it's wrong here
Sets the delay but does not enable restarting on failure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse `Restart=on-failure` with `Restart=always`, not realizing that `always` restarts even on clean exits (e.g., `systemctl stop`), which would interfere with manual service management.
Detailed technical explanation
How to think about this question
Under the hood, systemd uses the `Restart=` directive to define the restart policy based on the exit status or signal. `on-failure` specifically matches exit codes that are not 0, signals like SIGABRT or SIGSEGV, and timeouts. The `RestartSec=` directive introduces a sleep before the next restart, which is useful to prevent rapid restart loops (thundering herd) and to allow resources to settle. In real-world scenarios, a 10-second delay gives the system time to release file handles or network ports before the Python script restarts.
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 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
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.
Service Configuration — This question tests Service Configuration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Restart=on-failure
RestartSec=10 — Option B is correct because `Restart=on-failure` ensures the service restarts only when it exits with a non-zero exit code or is terminated by a signal (e.g., SIGKILL), which matches the 'crashes' scenario. Adding `RestartSec=10` introduces a 10-second delay before the restart attempt, as required. The other options either restart on success (irrelevant) or always restart (which would restart even on intentional stops), or omit the restart condition entirely.
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.
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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