This LFCS practice question tests your understanding of networking. 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.
After editing /etc/sysconfig/network-scripts/ifcfg-eth0, the network service fails to start. Which is the best command to investigate?
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.
nmcli device status
Why wrong: This shows device status, not why the service failed.
systemctl status NetworkManager
This shows the current status and recent errors of the NetworkManager service.
journalctl -u NetworkManager
Why wrong: This shows detailed logs, but the service status command is a better initial step.
ip link show eth0
Why wrong: This shows link state, not service failure reasons.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
systemctl status NetworkManager
The best command to investigate why the network service fails to start after editing an interface configuration file is `systemctl status NetworkManager`, because it shows the current state, recent log entries, and any error messages from the NetworkManager service. Since NetworkManager is the default network service on modern RHEL/CentOS systems, checking its status directly reveals whether it failed to reload or start, and often includes the specific configuration error.
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.
nmcli device status
Why it's wrong here
This shows device status, not why the service failed.
systemctl status NetworkManager
Why this is correct
This shows the current status and recent errors of the NetworkManager service.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
journalctl -u NetworkManager
Why it's wrong here
This shows detailed logs, but the service status command is a better initial step.
ip link show eth0
Why it's wrong here
This shows link state, not service failure reasons.
Common exam traps
The trap here is that candidates often pick `journalctl -u NetworkManager` because it shows logs, but the LFCS exam expects you to know that `systemctl status` is the first-line diagnostic tool for service failures, as it provides a quick summary of the service state and recent errors without needing to filter through all logs.
Trap categories for this question
Command / output trap
This shows device status, not why the service failed.
Detailed technical explanation
Under the hood, `systemctl status NetworkManager` queries systemd for the unit's state, including its main PID, exit code, and the last 10 lines of its journal. This is critical because NetworkManager parses files in `/etc/sysconfig/network-scripts/` on startup; a typo like `DEVICE=eth0` instead of `DEVICE=eth0` or an invalid `BOOTPROTO` value will cause the service to fail with a specific error message (e.g., 'Error: Connection activation failed'). In a real-world scenario, after editing `ifcfg-eth0`, running `systemctl status NetworkManager` immediately reveals if the service entered a 'failed' state and shows the exact line causing the issue, saving time over grepping logs.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
The correct answer is: systemctl status NetworkManager — The best command to investigate why the network service fails to start after editing an interface configuration file is `systemctl status NetworkManager`, because it shows the current state, recent log entries, and any error messages from the NetworkManager service. Since NetworkManager is the default network service on modern RHEL/CentOS systems, checking its status directly reveals whether it failed to reload or start, and often includes the specific configuration error.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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.
Read the scenario before looking for a memorised answer.
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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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