LFCS Operation of Running Systems Practice Question
A Linux server is configured to boot into a graphical target, but after a recent kernel update, the system hangs at a black screen after the GRUB menu. You can still access a rescue shell via the installation media. Which command should you use to make the system boot into a multi-user text target by default, allowing you to troubleshoot?
⚠ Common exam trap
Many candidates confuse systemctl isolate (runtime change) with systemctl set-default (persistent change).
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
✓
systemctl set-default multi-user.target
The default systemd target is managed via the default.target symbolic link. To change it persistently, the systemctl set-default command is used. Setting it to multi-user.target ensures the system boots to a text console, allowing the administrator to diagnose the graphical failure. This is the standard method for altering the default runlevel equivalent in systemd-based distributions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
systemctl isolate multi-user.target
Why it's wrong here
The isolate subcommand immediately switches the running system to the specified target, but it does not change the default boot target. After a reboot, the system would still attempt to start graphical.target, which is not helpful for a persistent fix. It is useful for temporary runtime changes, not for altering boot behavior.
- ✗
grub2-mkconfig -o /boot/grub2/grub.cfg
Why it's wrong here
This command regenerates the GRUB configuration file, typically after modifying /etc/default/grub. It does not change the systemd default target. While it could be used to modify kernel parameters, it does not directly address switching the default target to multi-user. It is not the correct tool for this scenario.
- ✓
systemctl set-default multi-user.target
Why this is correct
This command sets the default boot target to multi-user.target, which starts a text-based multi-user environment without a graphical display manager. It is the correct approach to bypass the graphical target and gain a usable console for troubleshooting. The change is persistent and can be reverted once the issue is resolved.
- ✗
systemctl enable multi-user.target
Why it's wrong here
Enabling a target creates symbolic links for dependencies but does not set it as the default boot target. The default target is controlled by the default.target symlink, which is changed with set-default. Enabling multi-user.target would not override the graphical target, so the system would still attempt to start the graphical interface.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Linux Foundation exam blueprint
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.