This LFCS practice question tests your understanding of networking. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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/resolv.conf to set a custom DNS server, the changes are reverted after reboot. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
NetworkManager manages DNS and overwrites manual changes
NetworkManager actively manages network interfaces and DNS settings by default on many Linux distributions. When a user manually edits /etc/resolv.conf, NetworkManager detects the change and overwrites it with its own configuration, especially after a reboot or network restart, because it treats the file as a managed resource. This is the most common reason for DNS changes being reverted.
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.
✗
The DHCP client overwrites resolv.conf on lease renewal
Why it's wrong here
Only if the interface is DHCP-enabled; static editing may still be overwritten by NetworkManager.
✗
SELinux reinitializes the file from defaults
Why it's wrong here
SELinux does not alter resolv.conf.
✓
NetworkManager manages DNS and overwrites manual changes
Why this is correct
NetworkManager updates resolv.conf based on its configuration; to persist manual changes, set dns=none in NetworkManager.conf.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
systemd-resolved regenerates the file from configuration
Why it's wrong here
systemd-resolved is not the default in RHEL/CentOS 7.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume DHCP client behavior (Option A) is the primary cause, but the LFCS exam focuses on NetworkManager as the default network service manager on modern enterprise Linux distributions like RHEL and CentOS.
Detailed technical explanation
How to think about this question
NetworkManager uses plugins like 'dnsmasq' or 'systemd-resolved' to handle DNS, and it writes to /etc/resolv.conf via the /etc/NetworkManager/NetworkManager.conf configuration file (specifically the 'dns' setting). When NetworkManager is running, it treats /etc/resolv.conf as a generated file and will overwrite manual edits on events like network interface activation, DHCP lease renewal, or reboot. A common real-world scenario is a user setting a custom DNS server for a VPN or local network, only to find it reverted after a system restart because NetworkManager's default behavior overrides manual changes.
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 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
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.
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: NetworkManager manages DNS and overwrites manual changes — NetworkManager actively manages network interfaces and DNS settings by default on many Linux distributions. When a user manually edits /etc/resolv.conf, NetworkManager detects the change and overwrites it with its own configuration, especially after a reboot or network restart, because it treats the file as a managed resource. This is the most common reason for DNS changes being reverted.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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