The answer is that another process is already listening on port 22. This is correct because the sshd service requires exclusive access to port 22 to bind and listen for incoming SSH connections; when the kernel returns the error “bind: Address already in use,” it means a conflicting process—often a lingering sshd instance or another service—has already claimed that port. On the CompTIA Linux+ XK0-005 exam, this scenario tests your ability to diagnose service startup failures using tools like `ss -tlnp` or `lsof -i :22` to identify the offending PID, then kill it with `kill` or `systemctl restart sshd`. A common trap is assuming the error is a firewall or configuration issue, but the core problem is always a port conflict. Memory tip: think “Port 22 is a one-seat ride—if someone’s already sitting, sshd can’t get on.”
XK0-005 System Management Practice Question
This XK0-005 practice question tests your understanding of system management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
# systemctl status sshd
● sshd.service - OpenSSH server daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; disabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Mon 2023-10-23 14:30:01 UTC; 5min ago
Docs: man:sshd(8)
man:sshd_config(5)
Process: 1234 ExecStart=/usr/sbin/sshd -D $OPTIONS (code=exited, status=255)
Main PID: 1234 (code=exited, status=255)
Oct 23 14:30:01 server sshd[1234]: fatal: Cannot bind to port 22: Address already in use
Based on the exhibit, what is the most likely cause of the sshd service failure?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
# systemctl status sshd
● sshd.service - OpenSSH server daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; disabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Mon 2023-10-23 14:30:01 UTC; 5min ago
Docs: man:sshd(8)
man:sshd_config(5)
Process: 1234 ExecStart=/usr/sbin/sshd -D $OPTIONS (code=exited, status=255)
Main PID: 1234 (code=exited, status=255)
Oct 23 14:30:01 server sshd[1234]: fatal: Cannot bind to port 22: Address already in use
A
The firewall is blocking port 22
Why wrong: Firewall would not cause 'address in use' error.
B
The sshd configuration file has incorrect permissions
Why wrong: Would show permission denied, not address in use.
C
The sshd service is not installed
Why wrong: The service file exists, so it is installed.
D
Another process is already listening on port 22
Error message directly indicates address already in use.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Another process is already listening on port 22
The sshd service failed because another process is already listening on port 22, which prevents sshd from binding to that port. This is indicated by the error message in the exhibit (e.g., 'bind: Address already in use'), which is a common symptom when a conflicting service or a previously running instance of sshd occupies the port. The system cannot start a new instance of sshd until the port is freed.
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.
The sshd configuration file has incorrect permissions
Why it's wrong here
Would show permission denied, not address in use.
✗
The sshd service is not installed
Why it's wrong here
The service file exists, so it is installed.
✓
Another process is already listening on port 22
Why this is correct
Error message directly indicates address already in use.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
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 assume a firewall or permission issue is the cause, but the specific 'Address already in use' error directly points to a port conflict, which is a distinct and common scenario on Linux systems.
Trap categories for this question
Command / output trap
Would show permission denied, not address in use.
Detailed technical explanation
How to think about this question
When sshd starts, it attempts to bind to TCP port 22 using the socket() and bind() system calls. If another process (e.g., a second sshd instance, a web server misconfigured to use port 22, or a leftover process) already holds that port, bind() fails with EADDRINUSE. Administrators can use 'ss -tlnp | grep :22' or 'lsof -i :22' to identify the conflicting PID and resolve the issue by killing the offending process or changing the port in sshd_config.
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 practitioner preparing for the XK0-005 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
System Management — This question tests System Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Another process is already listening on port 22 — The sshd service failed because another process is already listening on port 22, which prevents sshd from binding to that port. This is indicated by the error message in the exhibit (e.g., 'bind: Address already in use'), which is a common symptom when a conflicting service or a previously running instance of sshd occupies the port. The system cannot start a new instance of sshd until the port is freed.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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