This EX200 practice question tests your understanding of operate running systems. 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
● sshd.service - OpenSSH server daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Mon 2024-03-11 09:23:45 EDT; 5min ago
Process: 1234 ExecStart=/usr/sbin/sshd -D $OPTIONS (code=exited, status=255)
Main PID: 1234 (code=exited, status=255)
Status: "Failed to start sshd: Address already in use"
Based on the exhibit, what is the most likely cause of the 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.
Exhibit
● sshd.service - OpenSSH server daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Mon 2024-03-11 09:23:45 EDT; 5min ago
Process: 1234 ExecStart=/usr/sbin/sshd -D $OPTIONS (code=exited, status=255)
Main PID: 1234 (code=exited, status=255)
Status: "Failed to start sshd: Address already in use"
A
The SSH daemon is already running on another port.
Why wrong: The error is about address in use, not a port mismatch.
B
Another process is already listening on port 22.
Directly matches the error message.
C
The sshd configuration file has a syntax error.
Why wrong: A syntax error would show a different status, such as 'invalid argument'.
D
The service is not enabled.
Why wrong: The output shows 'enabled', so enablement is not the issue.
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 failure message indicates that the SSH daemon cannot start because port 22 is already in use. Option B is correct because the error 'Address already in use' or 'bind to port 22 failed' directly points to another process occupying the port, preventing sshd from binding. This is a common port conflict scenario, not a configuration syntax or service enablement issue.
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 SSH daemon is already running on another port.
Why it's wrong here
The error is about address in use, not a port mismatch.
✓
Another process is already listening on port 22.
Why this is correct
Directly matches the error message.
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.
✗
The sshd configuration file has a syntax error.
Why it's wrong here
A syntax error would show a different status, such as 'invalid argument'.
✗
The service is not enabled.
Why it's wrong here
The output shows 'enabled', so enablement is not the issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse a port conflict with a configuration syntax error or service enablement status, but the specific 'Address already in use' error message uniquely identifies a port binding conflict.
Trap categories for this question
Command / output trap
A syntax error would show a different status, such as 'invalid argument'.
Detailed technical explanation
How to think about this question
When sshd starts, it calls bind() on the configured port (default 22). If another process (e.g., a second SSH daemon, a web server misconfigured, or a leftover socket) already holds that port, the kernel returns EADDRINUSE. The 'ss -tlnp' or 'netstat -tulpn' command can identify the PID of the process listening on port 22. In real-world scenarios, this often occurs after a crash or when a previous sshd instance wasn't properly terminated, or when another service like a custom application inadvertently binds to the same port.
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 EX200 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.
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.
Operate running systems — This question tests Operate running systems — 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 failure message indicates that the SSH daemon cannot start because port 22 is already in use. Option B is correct because the error 'Address already in use' or 'bind to port 22 failed' directly points to another process occupying the port, preventing sshd from binding. This is a common port conflict scenario, not a configuration syntax or service enablement issue.
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.
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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