This EX200 practice question tests your understanding of manage security. 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.
Which THREE factors determine whether a local user can SSH into a Red Hat Enterprise Linux 9 system? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The user's shell is listed in /etc/shells.
Option C is correct because SSHd validates that the user's login shell is listed in /etc/shells before allowing authentication. If the shell is not present in /etc/shells (e.g., /sbin/nologin or a custom script), SSHd will deny the connection, even if the user has valid credentials. This check is controlled by the 'AllowUsers' and 'DenyUsers' directives but is a fundamental security measure to prevent users with non-standard shells from gaining interactive 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.
sshd checks if shell is valid; non-shell like /sbin/nologin prevents login.
Related concept
Read the scenario before looking for a memorised answer.
✓
The user's ~/.ssh/authorized_keys file exists and has correct permissions.
Why this is correct
Required for public key authentication.
Related concept
Read the scenario before looking for a memorised answer.
✓
The /etc/ssh/sshd_config file allows password or key authentication.
Why this is correct
Configuration directives control allowed methods.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the /etc/nologin file (which affects console logins) with the /etc/shells check (which affects SSH), or assume that sudo privileges imply SSH access, when in reality SSH authentication is independent of sudo.
Detailed technical explanation
How to think about this question
The /etc/shells check is enforced by the SSHd PAM module (pam_shells.so) which is typically included in the 'auth' stack for sshd. When a user's shell is not in /etc/shells, pam_shells.so returns PAM_AUTH_ERR, causing SSHd to deny the session before any password or key exchange occurs. This is a common hardening technique to prevent service accounts (e.g., with /sbin/nologin or /bin/false) from gaining interactive shell access, even if they have valid SSH keys. Note that the 'Match' directive in sshd_config can override this behavior for specific users or groups.
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.
Manage security — This question tests Manage security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The user's shell is listed in /etc/shells. — Option C is correct because SSHd validates that the user's login shell is listed in /etc/shells before allowing authentication. If the shell is not present in /etc/shells (e.g., /sbin/nologin or a custom script), SSHd will deny the connection, even if the user has valid credentials. This check is controlled by the 'AllowUsers' and 'DenyUsers' directives but is a fundamental security measure to prevent users with non-standard shells from gaining interactive access.
What should I do if I get this EX200 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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