LPIC-2 Linux Kernel and System Startup Practice Question
This LPIC-2 practice question tests your understanding of linux kernel and system startup. 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.
An administrator needs to disable IPv6 on a running system without rebooting and make the change permanent across reboots. Which set of commands should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6 && edit /etc/sysctl.conf to add net.ipv6.conf.all.disable_ipv6=1
Option B is correct because it combines a runtime sysctl command to immediately disable IPv6 on the running system without a reboot, and a persistent configuration in /etc/sysctl.conf to ensure the setting survives reboots. The /proc/sys/net/ipv6/conf/all/disable_ipv6 file controls the IPv6 stack at runtime, and sysctl.conf applies the kernel parameter at boot time.
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.
✗
modprobe -r ipv6
Why it's wrong here
Unloading the module may cause issues and is not reversible easily; also, it may not work if dependencies exist.
✓
echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6 && edit /etc/sysctl.conf to add net.ipv6.conf.all.disable_ipv6=1
Why this is correct
echo changes the runtime parameter; editing /etc/sysctl.conf makes it permanent. Both steps are necessary.
Related concept
Read the scenario before looking for a memorised answer.
✗
Edit /boot/grub/grub.cfg to add ipv6.disable=1
Why it's wrong here
This requires a reboot to take effect; it is not a runtime change.
✗
sysctl -w net.ipv6.conf.all.disable_ipv6=1
Why it's wrong here
This only changes the runtime value; it does not survive a reboot.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose Option D (sysctl -w) alone, forgetting that the question explicitly requires the change to be permanent across reboots, which necessitates editing a persistent configuration file like /etc/sysctl.conf.
Detailed technical explanation
How to think about this question
The sysctl parameter net.ipv6.conf.all.disable_ipv6 controls the entire IPv6 stack at the kernel level; setting it to 1 prevents IPv6 address assignment and routing for all interfaces, but the IPv6 kernel module remains loaded. In real-world scenarios, administrators often need to disable IPv6 temporarily for troubleshooting (e.g., to isolate network issues) without a full reboot, and then persist the change to avoid re-enabling after a planned maintenance reboot. Note that some distributions also require setting net.ipv6.conf.default.disable_ipv6=1 to prevent new interfaces from enabling IPv6.
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 LPIC-2 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.
Linux Kernel and System Startup — This question tests Linux Kernel and System Startup — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6 && edit /etc/sysctl.conf to add net.ipv6.conf.all.disable_ipv6=1 — Option B is correct because it combines a runtime sysctl command to immediately disable IPv6 on the running system without a reboot, and a persistent configuration in /etc/sysctl.conf to ensure the setting survives reboots. The /proc/sys/net/ipv6/conf/all/disable_ipv6 file controls the IPv6 stack at runtime, and sysctl.conf applies the kernel parameter at boot time.
What should I do if I get this LPIC-2 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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