The answer is that the container exited immediately after starting, which is the most likely cause of the connection refused error. When a container runs a command that finishes quickly—such as a shell script that exits or a process that terminates—the container stops, and no service remains listening on port 8080. This means the host’s TCP stack correctly refuses the connection because the container is no longer running to accept traffic. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of container lifecycle management and the critical difference between running a container in the foreground versus the background. A common trap is assuming the container is still active after the command completes, so always verify the container status with `docker ps -a` to see if it exited. Memory tip: “If the container exits, the port refuses”—a stopped container cannot serve connections, so check for a short-lived process before troubleshooting network settings.
XK0-005 Scripting, Containers and Automation Practice Question
This XK0-005 practice question tests your understanding of scripting, containers and automation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
```
$ cat Dockerfile
FROM ubuntu:22.04
RUN apt-get update && apt-get install -y nginx
COPY index.html /var/www/html/
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]
$ docker build -t webapp .
$ docker run -d -p 8080:80 webapp
```
After building and running the container as shown in the exhibit, the administrator tries to access http://localhost:8080 but receives a connection refused error. What is the most likely cause?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The container exited immediately after starting.
The most likely cause is that the container exited immediately after starting. When a container runs a command that finishes quickly (e.g., a shell script that exits), the container stops, and no process listens on port 8080. This results in a 'connection refused' error because the container is no longer running to accept connections.
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 container exited immediately after starting.
Why this is correct
Check docker ps to see if running.
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 port mapping is incorrect.
Why it's wrong here
Mapping is correct.
✗
The base image is not compatible.
Why it's wrong here
Ubuntu is compatible.
✗
The CMD syntax is incorrect.
Why it's wrong here
CMD syntax is valid.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between a container that fails to start (e.g., due to syntax errors) and one that starts but exits immediately, where the 'connection refused' error is a symptom of the latter.
Detailed technical explanation
How to think about this question
Containers run only as long as their main process (PID 1) is alive. If the Dockerfile's CMD or ENTRYPOINT runs a command like `echo` or a script that exits, the container stops. The 'connection refused' error occurs because the container is no longer in the running state; `docker ps` would show no container, while `docker ps -a` would show an 'Exited' status. This is a common pitfall when using minimal base images like Alpine that lack a long-running process by default.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Scripting, Containers and Automation — This question tests Scripting, Containers and Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The container exited immediately after starting. — The most likely cause is that the container exited immediately after starting. When a container runs a command that finishes quickly (e.g., a shell script that exits), the container stops, and no process listens on port 8080. This results in a 'connection refused' error because the container is no longer running to accept connections.
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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