The answer is that another service is already listening on port 80. This is the most likely cause because the nginx error message “bind() to 0.0.0.0:80 failed (98: Address already in use)” directly indicates that the port is occupied, preventing nginx from binding to it. On the CompTIA Cloud+ CV0-004 exam, this scenario tests your ability to interpret common service startup failures in cloud environments, where port conflicts are a frequent issue when deploying web servers. A common trap is confusing this with SELinux denials or configuration syntax errors, but the specific “address in use” wording points only to a port conflict. To remember, think of the mnemonic “Ports are like parking spots—if another car is there, you can’t park.”
CV0-004 Troubleshooting Practice Question
This CV0-004 practice question tests your understanding of troubleshooting. 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.
```
$ sudo systemctl status nginx
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Mon 2024-03-25 10:23:45 UTC; 1min 30s ago
Process: 12345 ExecStart=/usr/sbin/nginx (code=exited, status=1/FAILURE)
Main PID: 12345 (code=exited, status=1/FAILURE)
CGroup: /system.slice/nginx.service
Mar 25 10:23:45 web01 systemd[1]: Starting nginx...
Mar 25 10:23:45 web01 nginx[12345]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Mar 25 10:23:45 web01 nginx[12345]: nginx: [emerg] still could not bind()
```
A cloud administrator is starting the nginx web server on a new cloud VM but it fails. According to 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.
Refer to the exhibit.
```
$ sudo systemctl status nginx
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Mon 2024-03-25 10:23:45 UTC; 1min 30s ago
Process: 12345 ExecStart=/usr/sbin/nginx (code=exited, status=1/FAILURE)
Main PID: 12345 (code=exited, status=1/FAILURE)
CGroup: /system.slice/nginx.service
Mar 25 10:23:45 web01 systemd[1]: Starting nginx...
Mar 25 10:23:45 web01 nginx[12345]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Mar 25 10:23:45 web01 nginx[12345]: nginx: [emerg] still could not bind()
```
A
Another service is already listening on port 80
The error explicitly states address already in use.
B
The VM does not have network connectivity
Why wrong: The error shows the bind attempt; connectivity is not the issue.
C
SELinux is blocking nginx from binding to the port
Why wrong: SELinux would produce an AVC denial, not 'address in use'.
D
The nginx configuration file has a syntax error
Why wrong: Syntax errors would be reported differently, not as bind failure.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Another service is already listening on port 80
The error 'bind() to 0.0.0.0:80 failed (98: Address already in use)' indicates that port 80 is already occupied by another process. Option A is correct. Option B is wrong because SELinux would give a permission denied error, not address in use. Option C is wrong because the error says address in use, not file not found. Option D is wrong because the error is about binding, not about configuration syntax.
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.
✓
Another service is already listening on port 80
Why this is correct
The error explicitly states 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.
✗
The VM does not have network connectivity
Why it's wrong here
The error shows the bind attempt; connectivity is not the issue.
✗
SELinux is blocking nginx from binding to the port
Why it's wrong here
SELinux would produce an AVC denial, not 'address in use'.
✗
The nginx configuration file has a syntax error
Why it's wrong here
Syntax errors would be reported differently, not as bind failure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
The error shows the bind attempt; connectivity is not the issue.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 CV0-004 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 CV0-004 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Another service is already listening on port 80 — The error 'bind() to 0.0.0.0:80 failed (98: Address already in use)' indicates that port 80 is already occupied by another process. Option A is correct. Option B is wrong because SELinux would give a permission denied error, not address in use. Option C is wrong because the error says address in use, not file not found. Option D is wrong because the error is about binding, not about configuration syntax.
What should I do if I get this CV0-004 question wrong?
Identify which CV0-004 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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