Quick Answer
The answer is to add `AllowGroups ssh-users` to `/etc/ssh/sshd_config`. This directive works by instructing the SSH daemon to check the group membership of any user attempting to log in; only users who are members of the specified group—in this case, `ssh-users`—will be granted access, while all others are denied even if they have valid credentials. On the CompTIA Linux+ XK0-005 exam, this question tests your understanding of SSH access control directives, often contrasting `AllowGroups` with `AllowUsers` or `DenyGroups`. A common trap is confusing `AllowGroups` with `AllowUsers`—remember that `AllowGroups` checks group membership, not individual usernames. A helpful memory tip: think of "AllowGroups" as a bouncer checking for a group pass, not a guest list.
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 Linux server is configured to allow SSH access for remote administration. The security team wants to limit SSH access to only users in the 'ssh-users' group. Which configuration should be added to /etc/ssh/sshd_config?
AllowUsers ssh-users
Why wrong: AllowUsers expects usernames, not groups.
AllowGroups ssh-users
AllowGroups restricts SSH to group members.
DenyUsers root
Why wrong: This only denies root.
PermitRootLogin yes
Why wrong: This allows root login.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
AllowGroups ssh-users
Option B is correct because the AllowGroups directive in /etc/ssh/sshd_config restricts SSH logins to only those users who are members of the specified group. By setting 'AllowGroups ssh-users', only users belonging to the 'ssh-users' group will be permitted to authenticate via SSH, directly fulfilling the security team's requirement.
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.
AllowUsers ssh-users
Why it's wrong here
AllowUsers expects usernames, not groups.
AllowGroups ssh-users
Why this is correct
AllowGroups restricts SSH to group members.
Related concept
Read the scenario before looking for a memorised answer.
DenyUsers root
Why it's wrong here
This only denies root.
PermitRootLogin yes
Why it's wrong here
This allows root login.
Common exam traps
The trap here is that candidates confuse AllowUsers (which takes usernames) with AllowGroups (which takes group names), leading them to incorrectly select option A thinking it will filter by group membership.
Detailed technical explanation
The AllowGroups directive is processed by the sshd daemon during authentication; it checks the user's supplementary group memberships (as listed in /etc/group) against the specified group names. This directive can be combined with AllowUsers for more granular control, but when used alone, it applies to all users—meaning any user not in the allowed groups is denied, even if they have valid credentials. In a real-world scenario, this is often paired with a dedicated group like 'ssh-users' to enforce role-based access without modifying individual user configurations.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Security — This question tests Security — Read the scenario before looking for a memorised answer..
The correct answer is: AllowGroups ssh-users — Option B is correct because the AllowGroups directive in /etc/ssh/sshd_config restricts SSH logins to only those users who are members of the specified group. By setting 'AllowGroups ssh-users', only users belonging to the 'ssh-users' group will be permitted to authenticate via SSH, directly fulfilling the security team's requirement.
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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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An administrator wants to restrict SSH access to only users in the 'sshusers' group. Which configuration should be added to /etc/ssh/sshd_config?
mediumWhy C: Option C is correct because the `AllowGroups` directive in `/etc/ssh/sshd_config` restricts SSH login to users who are members of the specified group. By setting `AllowGroups sshusers`, only users belonging to the 'sshusers' group will be permitted to authenticate via SSH, while all others are denied. This matches the administrator's requirement precisely.
Variation 2. A system administrator needs to restrict SSH access to a Linux server to only users in the 'sshusers' group. Which configuration change achieves this?
easyWhy C: Option C is correct because the 'AllowGroups' directive in /etc/ssh/sshd_config restricts SSH access to only users who are members of the specified group. When set to 'AllowGroups sshusers', only users belonging to the 'sshusers' group will be permitted to log in via SSH, effectively blocking all others. This is the standard method for group-based access control in OpenSSH.
Variation 3. A systems administrator needs to restrict SSH access to a Linux server so that only users in the 'sshusers' group can log in. Which configuration change should be made in /etc/ssh/sshd_config?
mediumWhy C: Option C is correct because the 'AllowGroups' directive in /etc/ssh/sshd_config restricts SSH login to only users who are members of the specified group. By adding 'AllowGroups sshusers', only users in the 'sshusers' group will be permitted to authenticate via SSH, while all others are denied. This is the standard OpenSSH mechanism for group-based access control.
Variation 4. A system administrator wants to restrict SSH access to a specific group of users. Which two methods can achieve this? (Select TWO.)
easyWhy B: Option B is correct because the `AllowGroups` directive in `/etc/ssh/sshd_config` explicitly restricts SSH access to members of specified groups. When set to `AllowGroups engineers`, only users belonging to the 'engineers' group can authenticate via SSH, providing a straightforward and secure method for group-based access control.
Last reviewed: Jun 11, 2026
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