LFCS Operation of Running Systems Practice Question
A Linux server is experiencing performance issues. The administrator suspects that a process is causing excessive disk I/O. Which command should the administrator use to identify the process with the highest disk I/O usage in real-time?
⚠ Common exam trap
The trap here is assuming that top or iostat can show per-process disk I/O by default, but they do not; only iotop provides that granularity.
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
✓
iotop
The tool iotop is designed to monitor disk I/O usage per process in real-time. It displays a list of processes sorted by I/O, allowing the administrator to quickly identify the culprit. Other tools like top, iostat, and vmstat provide system-wide or per-device statistics but lack per-process I/O attribution, making them less effective for this specific troubleshooting task.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
iotop
Why this is correct
iotop is a specialized tool that displays real-time disk I/O usage by process. It shows which processes are reading from or writing to disk, along with the amount of I/O. This directly addresses the administrator's need to identify the process with the highest disk I/O. Running iotop (often with sudo) provides a top-like interface for I/O, making it the correct choice.
- ✗
vmstat 1
Why it's wrong here
vmstat reports virtual memory statistics, including processes, memory, paging, block I/O, traps, and CPU activity. While it can show overall block I/O, it does not break down I/O by process. The administrator needs to identify a specific process causing high I/O, and vmstat only provides system-wide metrics. Thus, it is not suitable for this scenario.
- ✗
top
Why it's wrong here
top provides real-time process monitoring, including CPU and memory usage, but by default it does not show disk I/O per process. It can display I/O if you toggle with 'f' and add the IO fields, but it is not the primary tool for disk I/O analysis. In this scenario, the administrator needs a tool specifically designed for I/O monitoring, so top is not the best choice.
- ✗
iostat -x 1
Why it's wrong here
iostat reports CPU and I/O statistics for devices and partitions, but it does not attribute I/O to individual processes. It shows aggregate device utilization, not per-process usage. While useful for identifying which disk is busy, it cannot pinpoint the process causing the I/O. Therefore, it does not meet the requirement of identifying the specific process.
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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 Linux Foundation exam blueprint
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.