The answer is `PermitRootLogin prohibit-password`. This directive in `/etc/ssh/sshd_config` specifically disables password-based authentication for the root user while still allowing key-based authentication, such as SSH public keys or GSSAPI credentials, to succeed. It directly satisfies the security policy of disabling root password login without blocking key-based access for any user, including root. On the CompTIA Linux+ XK0-005 exam, this question tests your understanding of SSH hardening directives and the distinction between authentication methods; a common trap is confusing `PermitRootLogin no` (which blocks all root login) with `prohibit-password`, which only blocks password logins. Remember the mnemonic: "Prohibit passwords, permit keys" — the directive name literally tells you it prohibits password authentication while leaving other methods open.
XK0-005 Security Practice Question
This XK0-005 practice question tests your understanding of security. 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.
A security policy requires that SSH root login be disabled, but key-based authentication for users should remain enabled. Which configuration line should be added to /etc/ssh/sshd_config?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
PermitRootLogin prohibit-password
The directive `PermitRootLogin prohibit-password` in `/etc/ssh/sshd_config` disables password-based authentication for the root user while still allowing key-based authentication (e.g., SSH public key or GSSAPI). This satisfies the security policy requirement to disable root login via passwords but retain the ability for users (including root) to authenticate using SSH keys.
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.
✗
PermitEmptyPasswords no
Why it's wrong here
This prevents empty passwords but does not affect root login method.
✗
PermitRootLogin no
Why it's wrong here
This disables all root logins, including key-based, which is more restrictive than needed.
✗
PasswordAuthentication yes
Why it's wrong here
This enables password authentication for all users, including root, which contradicts the policy.
✓
PermitRootLogin prohibit-password
Why this is correct
This disables password authentication for root while allowing key-based login.
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 `PermitRootLogin no` (which blocks all root SSH access) with `PermitRootLogin prohibit-password` (which only blocks password-based root access), leading them to choose option B when the question explicitly requires key-based authentication to remain enabled.
Detailed technical explanation
How to think about this question
The `prohibit-password` value (introduced in OpenSSH 6.2) is a more granular alternative to `without-password`; it blocks password and keyboard-interactive authentication for root but still permits public-key, host-based, and GSSAPI authentication. In practice, this allows automated administrative scripts or jump hosts to connect as root using SSH keys while preventing brute-force password attacks against the root account.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: PermitRootLogin prohibit-password — The directive `PermitRootLogin prohibit-password` in `/etc/ssh/sshd_config` disables password-based authentication for the root user while still allowing key-based authentication (e.g., SSH public key or GSSAPI). This satisfies the security policy requirement to disable root login via passwords but retain the ability for users (including root) to authenticate using SSH keys.
What should I do if I get this XK0-005 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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