This EX200 practice question tests your understanding of configure local storage. 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.
An administrator adds a new 100GB disk to a RHEL 9 server. Which command should be used first to verify that the kernel has detected the new disk?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
lsblk
The `lsblk` command lists all block devices detected by the kernel, including newly added disks, by reading the sysfs filesystem. It is the safest and most direct way to verify kernel detection without requiring root privileges or triggering side effects. Option D is correct because it immediately shows whether the 100GB disk appears in the device list.
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.
✗
udevadm trigger
Why it's wrong here
Incorrect. udevadm trigger forces udev to reprobe devices, not to verify detection.
✗
dmesg | grep sd
Why it's wrong here
Incorrect. dmesg shows kernel messages but is not the primary verification tool.
✗
fdisk -l
Why it's wrong here
Incorrect. fdisk -l lists partitions but requires root and is not the first step.
✓
lsblk
Why this is correct
Correct. lsblk displays all block devices and their attributes.
Clue confirmation
The clue words "first", "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
partprobe
Why it's wrong here
Incorrect. partprobe informs the kernel of new partitions, not to verify disk detection.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose `dmesg | grep sd` (Option B) because they recall kernel messages for SCSI disks, but this fails for non-SCSI devices (e.g., NVMe, virtio) and may miss the disk if the buffer has rotated, making `lsblk` the universal and correct first check.
Trap categories for this question
Command / output trap
Incorrect. dmesg shows kernel messages but is not the primary verification tool.
Detailed technical explanation
How to think about this question
Under the hood, `lsblk` reads `/sys/block/` entries, which are created by the kernel's block layer upon device discovery during boot or hotplug. A new disk may appear as `/dev/sdb`, `/dev/nvme0n1`, or `/dev/vdb` depending on the storage controller; `lsblk` shows all regardless of naming. In a real-world scenario, if the disk is not detected, checking `dmesg` for errors like 'unsupported device' or 'timeout' is a follow-up step, but `lsblk` is the first command to confirm presence.
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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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.
Configure local storage — This question tests Configure local storage — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: lsblk — The `lsblk` command lists all block devices detected by the kernel, including newly added disks, by reading the sysfs filesystem. It is the safest and most direct way to verify kernel detection without requiring root privileges or triggering side effects. Option D is correct because it immediately shows whether the 100GB disk appears in the device list.
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: "first", "which command". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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