Quick Answer
The correct answer is the `df` and `du` commands. These two standard Linux utilities serve complementary roles: `df` (disk free) reports the total, used, and available space on all mounted filesystems, giving you a high-level overview of disk usage across partitions, while `du` (disk usage) estimates the space consumed by individual files and directories, allowing you to drill down into specific paths. On the CompTIA Linux+ XK0-005 exam, this distinction is frequently tested to ensure you understand when to use each tool—`df` for filesystem-level capacity and `du` for per-directory consumption. A common trap is confusing `du` with `df` when asked for a system-wide check; remember that `df` shows free space on mounted volumes, whereas `du` calculates usage for a given path. For a quick memory tip: think “df for free” (filesystem free space) and “du for usage” (directory usage).
This XK0-005 practice question tests your understanding of troubleshooting. 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.
Which TWO commands can be used to check disk space usage on a Linux system?
mount
Why wrong: Shows mounted filesystems, not space usage.
lsof
Why wrong: Lists open files, not disk space.
du
Summarizes disk usage of files/directories.
fdisk
Why wrong: Manipulates partition tables, not usage.
df
Displays disk space usage for mounted filesystems.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
du
The `du` (disk usage) command estimates file and directory space usage, allowing you to check disk space consumed by specific paths. The `df` (disk free) command reports the total, used, and available space on mounted filesystems. Both are standard tools for inspecting disk space on Linux systems.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
mount
Why it's wrong here
Shows mounted filesystems, not space usage.
lsof
Why it's wrong here
Lists open files, not disk space.
du
Why this is correct
Summarizes disk usage of files/directories.
Related concept
Read the scenario before looking for a memorised answer.
fdisk
Why it's wrong here
Manipulates partition tables, not usage.
df
Why this is correct
Displays disk space usage for mounted filesystems.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates may confuse `du` and `df` with commands like `mount` or `fdisk`, which are related to filesystem management but do not directly report disk space usage.
Trap categories for this question
Command / output trap
Shows mounted filesystems, not space usage.
Detailed technical explanation
Under the hood, `df` reads filesystem metadata from the superblock (e.g., ext4's `s_blocks_count` and `s_free_blocks_count`) to calculate usage, while `du` traverses the directory tree and sums the `st_blocks` field from each inode's stat structure. A subtle behavior: `df` reports space used by reserved blocks (default 5% for ext4), which `du` does not account for, leading to slight discrepancies in reported usage.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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Troubleshooting — study guide chapter
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FAQ
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
The correct answer is: du — The `du` (disk usage) command estimates file and directory space usage, allowing you to check disk space consumed by specific paths. The `df` (disk free) command reports the total, used, and available space on mounted filesystems. Both are standard tools for inspecting disk space on Linux systems.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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