This LPIC-2 practice question tests your understanding of network client management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 configures LDAP authentication on a Linux client. After making changes to /etc/nsswitch.conf and /etc/pam.d/system-auth, users can log in but cannot execute commands like 'id username'. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
LDAP server is not reachable
Why wrong: Login works, so the server is reachable.
nsswitch.conf lacks 'ldap' for passwd
Id uses passwd map; if not set to ldap, it won't query LDAP.
LDAP binddn is missing
Why wrong: Binddn is for server authentication, not user lookups.
PAM configuration is incorrect
Why wrong: Login works, so PAM is fine.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
nsswitch.conf lacks 'ldap' for passwd
The 'id username' command relies on the Name Service Switch (NSS) to resolve user and group information from configured sources. If 'ldap' is not listed for the 'passwd' database in /etc/nsswitch.conf, the system will not query the LDAP server for user account details, even though PAM may have been configured to authenticate against LDAP. This mismatch allows login (via PAM) but prevents user attribute lookups (via NSS).
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.
LDAP server is not reachable
Why it's wrong here
Login works, so the server is reachable.
nsswitch.conf lacks 'ldap' for passwd
Why this is correct
Id uses passwd map; if not set to ldap, it won't query LDAP.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
LDAP binddn is missing
Why it's wrong here
Binddn is for server authentication, not user lookups.
PAM configuration is incorrect
Why it's wrong here
Login works, so PAM is fine.
Common exam traps
The trap here is that candidates assume LDAP authentication is fully functional because login succeeds, overlooking that NSS and PAM serve distinct roles—PAM handles authentication, while NSS handles user/group information retrieval—and both must be configured independently for LDAP integration to work completely.
Detailed technical explanation
The NSS 'passwd' database controls how the system resolves user account information (UID, GID, home directory, shell) via getpwnam() and getpwuid() calls. When 'ldap' is omitted from the 'passwd' line in /etc/nsswitch.conf, the system falls back to local files (/etc/passwd) and never queries the LDAP directory, even if PAM's pam_ldap module is correctly configured. This is a common split-brain scenario where authentication works (PAM) but identity resolution fails (NSS).
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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: nsswitch.conf lacks 'ldap' for passwd — The 'id username' command relies on the Name Service Switch (NSS) to resolve user and group information from configured sources. If 'ldap' is not listed for the 'passwd' database in /etc/nsswitch.conf, the system will not query the LDAP server for user account details, even though PAM may have been configured to authenticate against LDAP. This mismatch allows login (via PAM) but prevents user attribute lookups (via NSS).
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This LPIC-2 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-2 exam.
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