The answer is editing the /etc/inittab file to change the initdefault line. This is correct because SysV init reads the /etc/inittab file at boot to determine which runlevel to enter; the initdefault entry sets the default target, and modifying it permanently changes the system’s startup behavior. On the Linux Professional Institute Certification Level 1 LPIC-1 exam, this concept tests your understanding of the traditional init system, often contrasting it with systemd’s default.target symlink—a common trap is confusing the temporary runlevel change via telinit with the permanent change required here. To remember, think of inittab as the “init table” that holds the default runlevel, and editing it is the standard method for a persistent change. A useful mnemonic is “edit the tab to set the default lab.”
LPIC-1 System Architecture Practice Question
This LPIC-1 practice question tests your understanding of system architecture. 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.
Which TWO of the following are valid methods to change the default runlevel on a SysV init-based system?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Edit /etc/inittab to set the initdefault line.
In SysV init-based systems, the default runlevel is defined in the /etc/inittab file by the 'initdefault' line, which specifies the runlevel the system should enter after boot. Editing this line is the standard method to permanently change the default runlevel. Option B correctly identifies this mechanism.
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.
✗
Use the 'runlevel' command to set the default runlevel.
Why it's wrong here
The runlevel command only displays current and previous runlevels, it does not set defaults.
✓
Edit /etc/inittab to set the initdefault line.
Why this is correct
The initdefault line in /etc/inittab defines the default runlevel.
Related concept
Read the scenario before looking for a memorised answer.
✓
Pass the desired runlevel as a kernel parameter at boot time.
Why this is correct
Kernel parameters like '1' or 'single' override the default runlevel for the current boot.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use 'systemctl set-default' to set the default runlevel.
Why it's wrong here
systemctl is used on systemd-based systems, not SysV init.
✗
Use the 'telinit' command to change the default runlevel.
Why it's wrong here
telinit changes the current runlevel but does not set the default for future boots.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the 'runlevel' command (which only displays) with a command that can set the default, or they mistakenly apply systemd commands like 'systemctl set-default' to SysV init systems.
Trap categories for this question
Command / output trap
The runlevel command only displays current and previous runlevels, it does not set defaults.
Detailed technical explanation
How to think about this question
The /etc/inittab file uses a specific format where the 'initdefault' entry is identified by an 'id' field of a single colon-separated line, e.g., 'id:3:initdefault:'. The runlevel value (0-6, S, or s) is placed in the second field. When the init process reads this line, it sets the default runlevel for subsequent boots. A common real-world scenario is setting runlevel 3 for multi-user text mode or runlevel 5 for graphical mode, ensuring consistent boot behavior.
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-1 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.
System Architecture — This question tests System Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Edit /etc/inittab to set the initdefault line. — In SysV init-based systems, the default runlevel is defined in the /etc/inittab file by the 'initdefault' line, which specifies the runlevel the system should enter after boot. Editing this line is the standard method to permanently change the default runlevel. Option B correctly identifies this mechanism.
What should I do if I get this LPIC-1 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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