The answer is to add the user 'john' to the 'wheel' group and configure /etc/pam.d/su with pam_wheel.so using the 'trust' option. This works because the PAM (Pluggable Authentication Modules) framework, specifically the pam_wheel module, checks if the user belongs to a designated group—by default, 'wheel'—and when the 'trust' modifier is applied, it bypasses the password prompt entirely for that group during su transitions. On the Linux Foundation Certified System Administrator LFCS exam, this scenario tests your understanding of PAM stack control and group-based privilege escalation, often appearing as a distractor against sudo-based solutions; a common trap is confusing the 'trust' option with the 'require' option, which would instead force a password. Remember the mnemonic: "Wheel with trust means su without fuss."
LFCS User and Group Management Practice Question
This LFCS practice question tests your understanding of user and group 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.
An administrator needs to grant a user named 'john' the ability to switch to any other user without a password. Which TWO of the following steps are required to achieve this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add 'john' to the 'wheel' group and configure /etc/pam.d/su to use pam_wheel.so with the 'trust' option.
Option A is correct because adding 'john' to the 'wheel' group and configuring /etc/pam.d/su with pam_wheel.so and the 'trust' option allows members of the 'wheel' group to switch to any user via su without being prompted for a password. The 'trust' modifier in PAM bypasses the password authentication for users in the specified group, effectively granting passwordless su access.
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.
✓
Add 'john' to the 'wheel' group and configure /etc/pam.d/su to use pam_wheel.so with the 'trust' option.
Why this is correct
Correct: This allows members of the wheel group to su without a password if pam_wheel.so is configured.
Related concept
Read the scenario before looking for a memorised answer.
✓
Add a sudo rule: 'john ALL=(ALL) NOPASSWD: ALL' to /etc/sudoers.
Why this is correct
Correct: This allows 'john' to run any command as any user without a password via sudo.
Related concept
Read the scenario before looking for a memorised answer.
✗
Set the suid bit on /bin/su.
Why it's wrong here
Incorrect: The suid bit is already set on su; it does not bypass the password prompt.
✗
Run 'usermod -L john'.
Why it's wrong here
Incorrect: This locks the account, preventing any login.
✗
Add 'john' to the 'root' group.
Why it's wrong here
Incorrect: Being in the root group does not grant passwordless su.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse the 'wheel' group's traditional role in restricting su access (via pam_wheel.so without 'trust') with granting passwordless su, or they may incorrectly assume that adding a user to the 'root' group or locking the account would enable privilege escalation.
Detailed technical explanation
How to think about this question
The pam_wheel.so module in PAM (Pluggable Authentication Modules) controls access to su based on group membership; the 'trust' modifier allows users in the specified group (e.g., wheel) to authenticate without a password by returning PAM_SUCCESS immediately. In contrast, the sudo rule in option B uses the NOPASSWD tag in /etc/sudoers to allow 'john' to run any command as any user without a password, which is a different mechanism but also achieves the goal. Under the hood, PAM modules are stacked in /etc/pam.d/su, and the order of modules (e.g., pam_rootok.so, pam_wheel.so, pam_unix.so) determines authentication flow, with 'trust' skipping subsequent password checks.
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 LFCS 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.
User and Group Management — This question tests User and Group Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add 'john' to the 'wheel' group and configure /etc/pam.d/su to use pam_wheel.so with the 'trust' option. — Option A is correct because adding 'john' to the 'wheel' group and configuring /etc/pam.d/su with pam_wheel.so and the 'trust' option allows members of the 'wheel' group to switch to any user via su without being prompted for a password. The 'trust' modifier in PAM bypasses the password authentication for users in the specified group, effectively granting passwordless su access.
What should I do if I get this LFCS 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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