Question 1easymultiple choice
Full question →- A
-u 1001
Sets user ID inside container.
- B
-e USER=1001
Why wrong: Sets environment variable, not user.
- C
-v /host:/container
Why wrong: Mounts volume.
- D
--name mycontainer
Why wrong: Names container.
Question 132 of 510
Quick Answer
The answer is the `-u` (or `--user`) option, used with a specific user ID like `-u 1001`. This flag overrides the container’s default root user (UID 0) by mapping the container process to a host user ID, ensuring that files written to bind-mounted volumes inherit the correct ownership and avoid permission denied errors. On the CompTIA Linux+ XK0-005 exam, this concept tests your understanding of user namespace isolation and host-container file permission alignment, often appearing in scenario-based questions about shared storage or multi-user environments. A common trap is assuming the `--user` flag accepts a username only, but it also works with a numeric UID, which is critical when the host lacks a corresponding user entry. Remember the mnemonic: “Use `-u` for UID—match the number to avoid the blunder.”
XK0-005 Scripting, Containers and Automation Practice Question
This XK0-005 practice question tests your understanding of scripting, containers and automation. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
An administrator needs to run a container using a specific user ID to match host file permissions. Which Docker option should be used when running the container?
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
✓
-u 1001
The `-u` (or `--user`) option in Docker allows you to run the container process with a specific user ID (UID) instead of the default root (UID 0). By specifying `-u 1001`, the container's main process will run as UID 1001, which can be matched to a host user's UID to ensure proper file ownership and permissions when accessing mounted volumes. This is essential for avoiding permission denied errors when the container writes files to a bind-mounted host directory.
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.
- ✓
-u 1001
Why this is correct
Sets user ID inside container.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
-e USER=1001
Why it's wrong here
Sets environment variable, not user.
- ✗
-v /host:/container
Why it's wrong here
Mounts volume.
- ✗
--name mycontainer
Why it's wrong here
Names container.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse environment variables (like `-e USER=1001`) with the actual user ID change, mistakenly thinking setting an environment variable named `USER` will alter the process's effective UID, when in reality only `-u` or the `USER` directive in a Dockerfile changes the runtime user.
Detailed technical explanation
How to think about this question
Under the hood, the `-u` option translates to the Linux `setuid()` system call within the container's namespace, changing the real, effective, and saved user IDs of the container process. This is particularly important when using bind mounts with host files that have restrictive permissions (e.g., 0700 owned by UID 1001), as the container process must match that UID to read or write the files. A subtle behavior is that if the specified UID does not exist in the container's `/etc/passwd`, the process still runs with that numeric UID, but tools like `id` or `whoami` may show 'I have no name!'.
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.
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.
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Scripting, Containers and Automation — study guide chapter
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FAQ
Questions learners often ask
What does this XK0-005 question test?
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: -u 1001 — The `-u` (or `--user`) option in Docker allows you to run the container process with a specific user ID (UID) instead of the default root (UID 0). By specifying `-u 1001`, the container's main process will run as UID 1001, which can be matched to a host user's UID to ensure proper file ownership and permissions when accessing mounted volumes. This is essential for avoiding permission denied errors when the container writes files to a bind-mounted host directory.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This XK0-005 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 XK0-005 exam.
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