This LPIC-2 practice question tests your understanding of network client management. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 wants to restrict access to a service using PAM. Which file order determines the authentication flow for a service?
/etc/pam.d/<service-name>
Each service has its own PAM configuration file in /etc/pam.d/.
/etc/nsswitch.conf
Why wrong: This controls name service lookups, not authentication.
/etc/security/access.conf
Why wrong: This is an access control file, not the primary PAM configuration.
/etc/pam.conf
Why wrong: Although used, /etc/pam.d/ is preferred on modern systems.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
/etc/pam.d/<service-name>
PAM (Pluggable Authentication Modules) uses per-service configuration files located in /etc/pam.d/ to define the authentication flow. When a service (e.g., sshd, login) calls PAM, it reads the file named after the service (e.g., /etc/pam.d/sshd) to determine the order of modules (auth, account, password, session) and their control flags (required, requisite, sufficient, optional). This file-based approach allows fine-grained, service-specific authentication policies.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
/etc/pam.d/<service-name>
Why this is correct
Each service has its own PAM configuration file in /etc/pam.d/.
Related concept
Read the scenario before looking for a memorised answer.
/etc/nsswitch.conf
Why it's wrong here
This controls name service lookups, not authentication.
/etc/security/access.conf
Why it's wrong here
This is an access control file, not the primary PAM configuration.
/etc/pam.conf
Why it's wrong here
Although used, /etc/pam.d/ is preferred on modern systems.
Common exam traps
The trap here is that candidates confuse the PAM service configuration directory (/etc/pam.d/) with the legacy monolithic /etc/pam.conf or with unrelated system configuration files like /etc/nsswitch.conf or /etc/security/access.conf, which serve entirely different purposes in the authentication or name resolution pipeline.
Detailed technical explanation
Under the hood, when a PAM-aware application calls pam_start(), it passes the service name, and the PAM library searches /etc/pam.d/<service-name> first; if that file does not exist, it falls back to /etc/pam.d/other (the default policy). The control flags (required, requisite, sufficient, optional) determine whether a module's success or failure is critical to the overall authentication result, and the order of lines in the file dictates the module stack execution sequence. In real-world scenarios, misordering the stack (e.g., placing a 'sufficient' module before a 'required' one) can inadvertently bypass authentication checks.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the LPIC-2 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
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FAQ
Network Client Management — This question tests Network Client Management — Read the scenario before looking for a memorised answer..
The correct answer is: /etc/pam.d/<service-name> — PAM (Pluggable Authentication Modules) uses per-service configuration files located in /etc/pam.d/ to define the authentication flow. When a service (e.g., sshd, login) calls PAM, it reads the file named after the service (e.g., /etc/pam.d/sshd) to determine the order of modules (auth, account, password, session) and their control flags (required, requisite, sufficient, optional). This file-based approach allows fine-grained, service-specific authentication policies.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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