XK0-006 System Management Practice Question
Which command displays the amount of free and used disk space on all mounted file systems in a human-readable format?
⚠ Common exam trap
XK0-006 often tests the confusion between df (file system free space) and du (directory/file usage); candidates see '-h' and 'disk' in the question and pick du because it also measures disk usage.
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
✓
df -h
The df command reports file system disk space usage, and the -h flag renders sizes in human-readable units (K, M, G). Running df -h shows all mounted file systems with total, used, available space, and mount point. This is the standard Linux utility for checking free and used disk space.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
du -h /
Why it's wrong here
du -h / reports disk usage consumed by files and directories under the root path, not free space remaining on mounted filesystems. It is tempting because it shares the -h human-readable flag and reports disk consumption, but it measures directory contents rather than filesystem capacity, so it cannot show available space.
- ✗
lsblk -h
Why it's wrong here
lsblk lists block devices and their partitions, not filesystem usage; the -h flag there means help output rather than human-readable sizes. It is tempting because it reports disk-related information, and it would be correct for identifying device names and mount points, but df -h is the command that reports free and used space.
- ✗
mount -h
Why it's wrong here
mount -h prints the command's help text, not filesystem usage; it never queries mounted filesystems for capacity. It is tempting because mount lists mounted filesystems, so administrators associate it with disk information, but it reports mount options and device names, not free or used space.
- ✓
df -h
Why this is correct
`df -h` reports free and used space for every mounted file system, satisfying the "all mounted file systems" constraint. The `-h` flag converts block counts into human-readable units such as gigabytes, meeting the formatting requirement. Unlike `du`, which measures directory consumption, `df` queries file system statistics directly.
Go deeper
Related to this question
Learn chapter
Linux Fundamentals and History
Key term
Linux
Linux is an open-source operating system that manages computer hardware and software, widely used in servers, desktops, and embedded systems.
Key term
Mount
Mounting is the process of making a file system or storage device accessible to a computer's operating system by attaching it to a specific directory in the existing directory tree.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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