LFCS Storage Management Practice Question
A system administrator needs to identify all available block devices on a Linux server. Which two commands can be used to accomplish this? (Choose two.)
⚠ Common exam trap
Watch out — candidates often confuse `blkid` with `lsblk` because of similar names, but `blkid` only shows devices with filesystem metadata, not all block devices, making it incomplete for this task.
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
lsblk (C) is correct because it reads /sys/block and udev data to list all block devices in a tree view, showing disks, partitions, and their sizes, types, and mountpoints regardless of whether they are mounted. fdisk -l (E) is correct because it enumerates every block device in /proc/partitions and prints the partition table of each disk, making it a standard way to discover all available block devices. blkid (A) only reports devices that already have a filesystem or swap signature and their UUID/LABEL, so it misses unformatted or otherwise unrecognized block devices. mount (B) shows only currently mounted filesystems, not all block devices. df -h (D) reports disk space usage of mounted filesystems only, so it also fails to reveal unmounted or unformatted block devices.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
blkid
Why it's wrong here
blkid reports attributes of block devices that already have filesystems or signatures, so unformatted or unmapped devices may be omitted. lsblk enumerates all block devices regardless of filesystem. blkid is tempting because it lists devices, but it filters by identifiable content.
- ✗
mount
Why it's wrong here
mount with no arguments prints currently mounted filesystems from /proc/mounts, omitting any block device without a mountpoint. It is tempting because it shows storage in use, and it would be correct when the task is confirming which filesystems are mounted and their options.
- ✓
lsblk
Why this is correct
`lsblk` reads sysfs to list all block devices, showing disks, partitions, and their mountpoints in a tree. This directly satisfies the requirement to identify every available block device, including unmounted ones that filesystem-oriented tools would miss.
- ✗
df -h
Why it's wrong here
df -h reports mounted filesystems' space usage, reading /proc/mounts rather than enumerating block devices, so unmounted disks stay invisible. It is tempting because it lists storage, and it would be correct when the administrator needs free-space figures for existing filesystems.
- ✓
fdisk -l
Why this is correct
`fdisk -l` lists the partition tables of all detected block devices, printing each disk's size, sector count and partition layout without modifying anything. This directly satisfies the stem's requirement to identify every available block device, since it enumerates disks such as /dev/sda and /dev/nvme0n1 rather than only mounted filesystems.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.