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.
A system administrator is troubleshooting a DHCP issue on a Linux client. After running 'dhclient -r eth0' and then 'dhclient eth0', the interface does not get an IP address. What command can be used to ensure the DHCP client process is fully released and restarted?
dhclient -s 10.0.0.1 eth0
Why wrong: Specifying server is not necessary.
dhclient -r eth0 && dhclient -v eth0
Why wrong: This is essentially what the admin already tried.
killall dhclient && dhclient eth0
Why wrong: Killing may not cleanly release the lease.
dhclient -x eth0 && dhclient eth0
'-x' gracefully stops DHCP client, releasing the lease.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
dhclient -x eth0 && dhclient eth0
Option D is correct because `dhclient -x eth0` explicitly releases the current lease and terminates the DHCP client process for that interface, ensuring a clean state before restarting with `dhclient eth0`. This avoids issues where a stale process or lease file prevents a fresh DHCP handshake, which can occur with `-r` alone if the client daemon remains running.
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.
dhclient -s 10.0.0.1 eth0
Why it's wrong here
Specifying server is not necessary.
dhclient -r eth0 && dhclient -v eth0
Why it's wrong here
This is essentially what the admin already tried.
killall dhclient && dhclient eth0
Why it's wrong here
Killing may not cleanly release the lease.
dhclient -x eth0 && dhclient eth0
Why this is correct
'-x' gracefully stops DHCP client, releasing the lease.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates assume `-r` (release) followed by a new dhclient invocation is sufficient, but they overlook that the dhclient daemon may still be running and holding onto the old lease, whereas `-x` explicitly terminates the process and clears the lease state.
Detailed technical explanation
The `-x` option sends a DHCPRELEASE message to the server and then exits the dhclient process, removing the lease file from `/var/lib/dhcp/` (or similar). This is critical when the client’s lease database is corrupted or when the interface needs a completely fresh DHCP negotiation, as `-r` alone may leave the daemon running with cached state. In real-world scenarios, such as after a network segment change or server migration, using `-x` ensures the client does not reuse an invalid lease.
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.
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FAQ
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
The correct answer is: dhclient -x eth0 && dhclient eth0 — Option D is correct because `dhclient -x eth0` explicitly releases the current lease and terminates the DHCP client process for that interface, ensuring a clean state before restarting with `dhclient eth0`. This avoids issues where a stale process or lease file prevents a fresh DHCP handshake, which can occur with `-r` alone if the client daemon remains running.
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
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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