The answer is `Restart=on-failure`, which is the correct systemd service unit directive to ensure a service restarts only when it exits with a non-zero code, is killed by a signal, or times out. This directive is ideal because it distinguishes between intentional stops and actual failures, restarting the Python script precisely when the process terminates abnormally. On the CompTIA Linux+ XK0-005 exam, this concept tests your understanding of systemd service behavior and the critical difference between `Restart=on-failure` and `Restart=always`—a common trap where candidates choose the latter, not realizing it restarts even after a clean exit, which can mask administrator-initiated stops. The scenario often appears with a requirement to restart only on failure, such as after network availability is confirmed. A useful memory tip: think of "on-failure" as "only when it breaks," contrasting with "always" which means "even when it’s fine."
XK0-005 Scripting, Containers and Automation Practice Question
This XK0-005 practice question tests your understanding of scripting, containers and automation. 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.
An administrator is tasked with creating a systemd service that runs a Python script after the network is available. The script must restart automatically if it fails. Which systemd service unit directive should be used to ensure restart on failure?
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 instructs systemd to restart the service unit only when the process exits with a non-zero exit code, is terminated by a signal (including SIGKILL), or times out. This is the correct choice because the requirement is to restart the script only if it fails, not unconditionally. Using `Restart=always` would restart the service even after a clean exit, which is unnecessary and could mask intentional stops.
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=always
Why it's wrong here
Restarts the service regardless of exit status, which is not required and could cause unnecessary restarts on expected exits.
✗
RemainAfterExit=yes
Why it's wrong here
Marks the service as active even after the main process exits, but does not restart it.
✓
Restart=on-failure
Why this is correct
Restarts the service only when the process exits with a non-zero exit status or is terminated by a signal.
Related concept
Read the scenario before looking for a memorised answer.
✗
RestartSec=5
Why it's wrong here
Sets the time to wait before restarting, but does not enable restart itself.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between `Restart=always` and `Restart=on-failure`, trapping candidates who assume that 'always' is the safest choice without reading the exact failure condition requirement.
Detailed technical explanation
How to think about this question
Under the hood, systemd tracks the exit status of the main process via the `ExecStart=` command. When `Restart=on-failure` is set, systemd evaluates the exit code against its internal failure criteria, which include non-zero exit codes, abnormal termination signals, and service timeouts. A common subtlety is that `Restart=on-failure` will also restart the service if it is terminated by a signal like SIGKILL (exit code 137), which is useful for catching out-of-memory kills, whereas `Restart=always` would restart even after a `systemctl stop` command, potentially causing confusion.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Scripting, Containers and Automation — This question tests Scripting, Containers and Automation — 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 instructs systemd to restart the service unit only when the process exits with a non-zero exit code, is terminated by a signal (including SIGKILL), or times out. This is the correct choice because the requirement is to restart the script only if it fails, not unconditionally. Using `Restart=always` would restart the service even after a clean exit, which is unnecessary and could mask intentional stops.
What should I do if I get this XK0-005 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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