The answer is to select the old kernel from the 'Advanced options for Ubuntu' submenu within GRUB. This is correct because when a kernel update causes a panic, the GRUB bootloader retains the previous kernel image in its menu, allowing you to bypass the faulty version and boot into a stable environment. On the CompTIA Linux+ XK0-005 exam, this scenario tests your ability to recover from a failed update by navigating GRUB’s advanced options, a common troubleshooting step that traps candidates who forget to make the fix persistent. After booting the old kernel, you must edit /etc/default/grub to set GRUB_DEFAULT to 'saved' and run update-grub, ensuring the system defaults to the last working kernel on subsequent reboots. Remember the mnemonic "Select, Save, Update" — select the old kernel, save the default, and update GRUB configuration.
XK0-005 System Management Practice Question
This XK0-005 practice question tests your understanding of system management. 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.
A Linux system is experiencing kernel panics after a recent update. The administrator wants to boot into a previous kernel version to restore functionality. Which three steps are required to achieve this? (Select THREE).
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
After booting, edit /etc/default/grub and set GRUB_DEFAULT to the saved entry, then run update-grub
Option A is correct because after booting into a working kernel, editing /etc/default/grub to set GRUB_DEFAULT to 'saved' and running update-grub (or grub-mkconfig) ensures that the GRUB bootloader will remember and default to the last successfully booted kernel, which can be the previous version. This step is necessary to make the temporary fix persistent across reboots.
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.
✓
After booting, edit /etc/default/grub and set GRUB_DEFAULT to the saved entry, then run update-grub
Why this is correct
Makes the old kernel the default for future boots.
Related concept
Read the scenario before looking for a memorised answer.
✓
At the GRUB menu, press 'e' to edit the boot entry
Why this is correct
Needed to see kernel options.
Related concept
Read the scenario before looking for a memorised answer.
✗
Run 'yum reinstall kernel' to revert to the previous version
Why it's wrong here
Reinstalling may not restore the old kernel configuration.
✗
Edit /etc/fstab to change root filesystem parameters
Why it's wrong here
Unrelated to kernel selection.
✓
Select the old kernel from the 'Advanced options for Ubuntu' submenu
Why this is correct
Allows booting the previous kernel.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between temporary boot fixes (editing GRUB entries at boot time) and permanent configuration changes (editing /etc/default/grub and running update-grub), and candidates may mistakenly think that reinstalling the kernel package reverts to a previous version.
Detailed technical explanation
How to think about this question
GRUB uses the GRUB_DEFAULT variable in /etc/default/grub to determine which menu entry to boot; setting it to 'saved' enables the 'grub-set-default' and 'grub-reboot' commands to persist the last chosen kernel. The 'update-grub' command (which is a wrapper for grub-mkconfig) regenerates the /boot/grub/grub.cfg file, incorporating changes from /etc/default/grub and scanning for installed kernels in /boot.
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 XK0-005 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
System Management — This question tests System Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: After booting, edit /etc/default/grub and set GRUB_DEFAULT to the saved entry, then run update-grub — Option A is correct because after booting into a working kernel, editing /etc/default/grub to set GRUB_DEFAULT to 'saved' and running update-grub (or grub-mkconfig) ensures that the GRUB bootloader will remember and default to the last successfully booted kernel, which can be the previous version. This step is necessary to make the temporary fix persistent across reboots.
What should I do if I get this XK0-005 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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A Linux server with systemd is experiencing boot issues after a recent kernel update. Which command sequence should be used to boot into the previous kernel version?
medium
A.Boot from a live CD and run 'rpm -Uvh --oldkernel' to revert the kernel.
✓ B.Interrupt the boot process, select 'Advanced options' in GRUB, then choose the previous kernel.
C.Use 'systemctl set-default multi-user.target' and reboot.
D.Use 'grub2-set-default' with the previous kernel entry before rebooting.
Why B: Option B is correct because GRUB (Grand Unified Bootloader) stores multiple kernel versions in its menu. By interrupting the boot process and selecting 'Advanced options for Ubuntu' (or similar), you can choose the previous kernel entry, which loads the older kernel and its associated initramfs. This is the standard method to recover from a failed kernel update on systems using systemd and GRUB.
Variation 2. After a kernel upgrade, the system fails to boot. Which file should be edited to configure GRUB2 to boot into the previous kernel version by default?
hard
A./etc/grub.d/40_custom
B./boot/grub/grub.conf
C./boot/grub2/grub.cfg
✓ D./etc/default/grub
Why D: /etc/default/grub is the configuration file for GRUB2. After editing, run grub2-mkconfig to regenerate grub.cfg. Directly editing grub.cfg is overwritten on updates. /boot/grub2/grub.cfg is auto-generated. /etc/grub.d/40_custom is for custom entries.
Last reviewed: Jun 30, 2026
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