LFCS Operation of Running Systems Practice Question
A Linux server is experiencing performance degradation. The administrator suspects that a process is consuming excessive CPU. Which two commands can be used to identify the top CPU-consuming processes in real-time? (Choose two.)
⚠ Common exam trap
The trap here is thinking that any command showing CPU statistics will identify the specific process; only per-process tools like top or ps do that.
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
✓
top
To identify top CPU-consuming processes, tools that show per-process CPU usage are needed. top provides a real-time, interactive view, while ps aux --sort=-%cpu gives a sorted snapshot. Both allow the administrator to see which processes are using the most CPU. vmstat and iostat show system-wide CPU statistics but not per-process details, and free is for memory. Therefore, top and ps with sorting are the correct choices.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
top
Why this is correct
The top command provides a dynamic, real-time view of running processes, sorted by CPU usage by default. It displays %CPU, making it easy to identify processes consuming the most CPU. It also allows interactive sorting and killing of processes. This is a standard tool for performance troubleshooting.
- ✗
vmstat 1
Why it's wrong here
vmstat reports virtual memory statistics, including CPU usage, but does not show per-process CPU consumption. It provides system-wide CPU utilization, which can indicate if CPU is a bottleneck but cannot identify which process is responsible. Therefore, it does not fulfill the requirement to identify top CPU-consuming processes.
- ✗
free -m
Why it's wrong here
free displays memory usage, including total, used, and free memory. It does not provide any CPU usage information, per-process or otherwise. It is irrelevant to identifying CPU-consuming processes. This command would not help in diagnosing high CPU usage.
- ✓
ps aux --sort=-%cpu
Why this is correct
The ps command with --sort=-%cpu lists processes sorted by CPU usage in descending order. While it provides a snapshot rather than real-time updates, it quickly shows the top CPU consumers. This is useful for scripting and one-time checks. It meets the requirement of identifying top CPU-consuming processes.
- ✗
iostat -c
Why it's wrong here
iostat displays CPU and I/O statistics, but like vmstat, it reports system-wide averages and does not break down CPU usage per process. It is useful for diagnosing I/O bottlenecks but not for pinpointing a specific process consuming CPU. Thus, it is not suitable for this task.
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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.