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.
Which TWO commands can be used to view logs for a specific systemd unit (e.g., sshd.service)?
tail -f /var/log/secure
Why wrong: Not default for systemd units.
systemctl status sshd.service
Why wrong: Shows recent logs but not full log view.
cat /var/log/messages | grep sshd
Why wrong: Traditional syslog, not systemd-journald focused.
journalctl -u sshd.service
Standard way to view unit logs.
journalctl _SYSTEMD_UNIT=sshd.service
Alternative using journal fields.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
journalctl -u sshd.service
Both `journalctl -u sshd.service` and `journalctl _SYSTEMD_UNIT=sshd.service` are correct because `journalctl` is the native tool for querying the systemd journal, which stores logs for all systemd units. The `-u` flag filters by unit name, while `_SYSTEMD_UNIT=` is a journal field that directly matches the unit identifier, both providing the same filtered output for sshd.service.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
tail -f /var/log/secure
Why it's wrong here
Not default for systemd units.
systemctl status sshd.service
Why it's wrong here
Shows recent logs but not full log view.
cat /var/log/messages | grep sshd
Why it's wrong here
Traditional syslog, not systemd-journald focused.
journalctl -u sshd.service
Why this is correct
Standard way to view unit logs.
Related concept
Read the scenario before looking for a memorised answer.
journalctl _SYSTEMD_UNIT=sshd.service
Why this is correct
Alternative using journal fields.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates may think `systemctl status` is a log viewing command, but it only shows a brief snippet of recent logs and is not designed for comprehensive log retrieval, while `journalctl` is the correct tool for accessing the full journal.
Trap categories for this question
Command / output trap
Shows recent logs but not full log view.
Detailed technical explanation
The systemd journal stores logs in a binary format under `/var/log/journal/` (or `/run/log/journal/` if persistent storage is disabled), allowing structured metadata fields like `_SYSTEMD_UNIT`, `_PID`, and `_COMM` to be queried with `journalctl`. This enables precise filtering without parsing text files, and the journal can be queried across boots using `--boot` flags. In real-world scenarios, using `journalctl -u sshd.service -f` provides a live tail of SSH logs, which is more reliable than monitoring `/var/log/secure` on systems where syslog-ng or rsyslog is not configured.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Operation of Running Systems — This question tests Operation of Running Systems — Read the scenario before looking for a memorised answer..
The correct answer is: journalctl -u sshd.service — Both `journalctl -u sshd.service` and `journalctl _SYSTEMD_UNIT=sshd.service` are correct because `journalctl` is the native tool for querying the systemd journal, which stores logs for all systemd units. The `-u` flag filters by unit name, while `_SYSTEMD_UNIT=` is a journal field that directly matches the unit identifier, both providing the same filtered output for sshd.service.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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