EX200 Configure local storage Practice Question
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?
⚠ Common exam trap
Test-takers frequently 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.
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
✓
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.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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udevadm trigger
Why it's wrong here
udevadm trigger is a management command that manually generates synthetic uevents, forcing udev to reprocess device rules for existing devices. It does not query kernel state or confirm that a newly installed disk is present; it simply re-applies device configuration. Since the hotplug system already detects the disk automatically, running trigger is unnecessary for verification and can even cause duplicate events or rule re-execution.
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dmesg | grep sd
Why it's wrong here
dmesg | grep sd displays kernel ring-buffer messages related to SCSI disk drivers, such as 'sd 0:0:0:0: Attached SCSI disk'. However, this is a raw log-viewing technique that requires the relevant messages to still be in the buffer and involves noisy, non-structured output. It does not give a clean, current inventory of block devices, and would miss non-sd devices like nvme0n1 or vda, making it an unreliable validation method.
- ✗
fdisk -l
Why it's wrong here
fdisk -l enumerates disk partition tables and, while it will reveal a newly attached disk, it requires root privileges and focuses on partitioning information rather than kernel device recognition. Running fdisk as a first verification step can be excessive, because the tool can modify disk structures if invoked without the right flags, and its output is noisy on systems with multipath or many LUNs. The immediate need is simply to confirm the device node exists, which lsblk does.
- ✓
lsblk
Why this is correct
lsblk reads block device information directly from sysfs and the kernel device model, listing every attached disk, partition, and relevant attributes such as size, type, and mountpoint. It works without elevated privileges and produces a clean, easily parseable tree that immediately shows the newly added 100GB disk via its NAME and SIZE columns. Because it reflects the live kernel view, lsblk is the standard, first-line tool for verifying that a disk is detected.
- ✗
partprobe
Why it's wrong here
partprobe is a utility that asks the kernel to re-read an existing disk's partition table, often after running fdisk or parted to add or delete partitions. It neither scans for new disks nor confirms the operating system recognizes an added disk; its purpose is purely synchronizing partition table changes. If a disk is not visible to the kernel, partprobe has nothing to act on and produces no meaningful confirmation, so it is not a detection-verification tool.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This EX200 practice question is part of Courseiva's free Red Hat 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 EX200 exam.