XK0-006 Security Practice Question
A firewall administrator wants to add a rule to allow incoming SSH traffic (port 22) using firewalld. Which command correctly adds this rule to the default zone permanently?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
firewall-cmd --add-service=ssh --permanent
firewall-cmd --add-service=ssh --permanent adds the SSH service permanently. Option A lacks --permanent, Option C is missing the required protocol specification (e.g., /tcp), and Option D lacks --permanent. While --add-port=22/tcp would also work, --add-service is more descriptive and easier to manage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
firewall-cmd --add-port=22/tcp
Why it's wrong here
This command adds port 22/tcp but without the --permanent flag, so it only affects the runtime configuration, not the permanent configuration.
- ✓
firewall-cmd --add-service=ssh --permanent
Why this is correct
Correct. This command adds the ssh service permanently to the default zone using the --permanent flag.
- ✗
firewall-cmd --add-port=22 --permanent
Why it's wrong here
This command is incorrect because it lacks the protocol (/tcp) specification. The correct syntax requires the protocol (e.g., 22/tcp) when using --add-port.
- ✗
firewall-cmd --zone=public --add-service=ssh
Why it's wrong here
This command adds the ssh service to the public zone, but it does not include the --permanent flag, so the rule is not permanent. Also, the question specifies the default zone, so specifying a zone is unnecessary.
Go deeper
Related to this question
Learn chapter
Firewall and Security Basics
Key term
Service
A service is a software component or system that performs a specific function and is available to be used by other programs or users over a network.
Key term
SSH
SSH (Secure Shell) is a cryptographic network protocol that provides secure, encrypted communication and remote administration between two devices over an unsecured network.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This XK0-006 practice question is part of Courseiva's free CompTIA 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 XK0-006 exam.