The answer is `Restart=on-failure`, which is the correct systemd directive to configure a service to restart automatically when it crashes. This directive works by instructing systemd to restart the unit whenever the process exits with a non-zero exit code, is terminated by a signal (such as SIGKILL), or hits a timeout—exactly the conditions that define a crash for a TCP application listening on port 8080. On the Linux Foundation Certified System Administrator LFCS exam, this question tests your understanding of service reliability and unit file options, often appearing alongside `Restart=always` as a distractor; the key trap is that `always` restarts even on clean exits, which is unnecessary here. Remember that `on-failure` is the precise choice for crash recovery because it ignores intentional stops. A helpful mnemonic: “Failure triggers the fix—on-failure is your restart pick.”
LFCS Service Configuration Practice Question
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 server runs a custom application that listens on TCP port 8080. The administrator wants to ensure the application starts automatically on boot and restarts if it crashes. Which systemd unit file directive should be used to achieve the restart behavior?
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
The `Restart=on-failure` directive in a systemd unit file instructs systemd to automatically restart the service unit when it exits with a non-zero exit code, is terminated by a signal (including SIGKILL), or times out. This directly satisfies the requirement for the application to restart if it crashes, as a crash typically results in an unclean exit that triggers the restart condition.
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.
✗
RestartSec=5
Why it's wrong here
RestartSec sets the delay before restart, but does not enable restarting.
✗
Type=notify
Why it's wrong here
Type=notify is used for services that notify systemd when they are ready, unrelated to restart.
✗
RemainAfterExit=yes
Why it's wrong here
RemainAfterExit keeps the service as active even if the main process exits, but does not restart it.
✓
Restart=on-failure
Why this is correct
This directive tells systemd to restart the service when it exits unexpectedly.
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 `RestartSec` with the restart policy itself, or assume `Type=notify` or `RemainAfterExit=yes` imply automatic restart behavior, when in fact only `Restart=` directives control restart logic.
Detailed technical explanation
How to think about this question
Under the hood, systemd tracks the exit status and signal of the service's main PID. When `Restart=on-failure` is set, systemd evaluates the exit cause against a predefined set of 'failure' conditions (e.g., non-zero exit code, abnormal signal, watchdog timeout). This is part of systemd's service lifecycle management, which also supports `Restart=always` for unconditional restarts and `Restart=on-abnormal` for more specific failure modes. In production, combining `Restart=on-failure` with `RestartSec=5` and `StartLimitIntervalSec=30` prevents restart loops while ensuring resilience.
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 — The `Restart=on-failure` directive in a systemd unit file instructs systemd to automatically restart the service unit when it exits with a non-zero exit code, is terminated by a signal (including SIGKILL), or times out. This directly satisfies the requirement for the application to restart if it crashes, as a crash typically results in an unclean exit that triggers the restart condition.
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.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. 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?
hard
A.Restart=on-success
RestartSec=10
✓ B.Restart=on-failure
RestartSec=10
C.Restart=always
RestartSec=10
D.RestartSec=10
Why B: 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.
Last reviewed: Jun 11, 2026
Question Discussion
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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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