This LPIC-1 practice question tests your understanding of administrative tasks. 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 adds the line 'DenyUsers john' to /etc/ssh/sshd_config and restarts the SSH service. What is the effect?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
User john cannot log in via SSH.
The 'DenyUsers' directive in /etc/ssh/sshd_config explicitly blocks the specified user(s) from authenticating via SSH. When the SSH service is restarted, the configuration is reloaded, and user 'john' will be denied SSH login attempts at the authentication layer, before any shell or command execution occurs.
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.
✓
User john cannot log in via SSH.
Why this is correct
This is the intended behavior of the DenyUsers directive.
Related concept
Read the scenario before looking for a memorised answer.
✗
User john can still log in but his commands are logged.
Why it's wrong here
DenyUsers blocks login entirely, not just logging.
✗
User john is denied all shell access, including local and console logins.
Why it's wrong here
DenyUsers only affects SSH, not local console or other remote access methods.
✗
All users except john cannot log in via SSH.
Why it's wrong here
That would be the effect of AllowUsers, not DenyUsers.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'DenyUsers' with broader access restrictions like PAM-based account denial or shell-level bans, but 'DenyUsers' is SSH-specific and only affects SSH logins, not console or other remote access methods.
Detailed technical explanation
How to think about this question
Under the hood, sshd reads the 'DenyUsers' list during authentication and immediately rejects the connection if the username matches, before password or key verification. This is implemented in the OpenSSH source code within the auth_check_user() function, and it works in conjunction with 'AllowUsers' and 'DenyGroups' for fine-grained access control. A real-world scenario is blocking a compromised account while allowing other users to continue working, without modifying PAM or system-level restrictions.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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.
Administrative Tasks — This question tests Administrative Tasks — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: User john cannot log in via SSH. — The 'DenyUsers' directive in /etc/ssh/sshd_config explicitly blocks the specified user(s) from authenticating via SSH. When the SSH service is restarted, the configuration is reloaded, and user 'john' will be denied SSH login attempts at the authentication layer, before any shell or command execution occurs.
What should I do if I get this LPIC-1 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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Question Discussion
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