LPIC-1 System Architecture Practice Question
Which TWO of the following are valid methods to change the default runlevel on a SysV init-based system?
⚠ Common exam trap
It's easy for candidates to 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.
Answer choices
Why each option matters
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.
Option B is correct because on a SysV init-based system the default runlevel is defined in /etc/inittab by the initdefault entry (e.g., id:3:initdefault:), which init reads at startup to determine which runlevel to enter. Option C is correct because passing a runlevel as a kernel boot parameter (e.g., appending '3' or 'single' to the kernel command line) overrides the initdefault setting for that boot, causing init to start in the specified runlevel. Option A is incorrect because the 'runlevel' command only reports the previous and current runlevels; it does not set them. Option D is incorrect because 'systemctl set-default' is a systemd command for setting the default target, not applicable to SysV init systems. Option E is incorrect because 'telinit' changes the runlevel of the currently running system immediately, but does not persistently alter the default runlevel configured in /etc/inittab.
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 reports the previous and current runlevel; it accepts no argument to set anything. It is tempting because it is a real SysV tool whose name matches the task, but its actual purpose is displaying state, not editing /etc/inittab's initdefault entry.
- ✓
Edit /etc/inittab to set the initdefault line.
Why this is correct
SysV init reads /etc/inittab at startup, and the initdefault line specifies which runlevel init enters by default. Editing that entry directly changes the persistent default runlevel, satisfying the requirement for a valid configuration method on a SysV init-based system.
- ✓
Pass the desired runlevel as a kernel parameter at boot time.
Why this is correct
Passing a runlevel number on the kernel command line overrides the initdefault value in /etc/inittab for that boot only, since init receives it as an argument. This is a valid one-off method to change the runlevel on a SysV init-based system.
- ✗
Use 'systemctl set-default' to set the default runlevel.
Why it's wrong here
SysV init reads the default runlevel from /etc/inittab, and systemctl belongs to systemd, which does not use runlevels at all. It is tempting because systemctl set-default is the genuine method for setting a systemd default target, which is the correct choice on a systemd-based distribution.
- ✗
Use the 'telinit' command to change the default runlevel.
Why it's wrong here
telinit changes the runlevel only for the current session; it does not alter the default recorded in /etc/inittab, so the change is lost on reboot. It is tempting because telinit genuinely switches runlevels immediately, which is correct when you need a one-off transition rather than a persistent default.
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This LPIC-1 practice question is part of Courseiva's free LPI 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 LPIC-1 exam.