Quick Answer
The correct commands are `iostat -x 1` and `iotop -o`. `iostat -x 1` provides extended disk statistics, including `%util` (the percentage of time the device was busy) and `await` (the average I/O service time), which directly reveal disk bottlenecks and I/O wait. `iotop -o` filters to show only processes actively performing I/O, pinpointing the specific culprit behind disk contention. On the CompTIA Linux+ XK0-005 exam, this question tests your ability to move beyond CPU/memory analysis when a server is unresponsive but `top` shows no obvious hog—a common trap is forgetting that high I/O wait can masquerade as a CPU issue. Remember the memory tip: “I/O wait? Check `iostat` for util, then `iotop` for the fool.”
This XK0-005 practice question tests your understanding of troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A Linux administrator is troubleshooting a server that has become unresponsive. The administrator connects via IPMI and runs 'top' but the process list does not show any obvious CPU or memory hog. Which TWO commands could be used to identify I/O wait issues or disk bottlenecks? (Choose TWO.)
iostat -x 1
iostat -x shows extended I/O statistics per device.
iotop -o
iotop -o shows only processes with I/O activity.
vmstat 1
Why wrong: vmstat shows system summary, not per-process I/O.
sar -b 1
Why wrong: sar -b shows I/O statistics but requires sysstat package and data collection.
dstat --disk-util
Why wrong: dstat can show disk utilization, but not as detailed as iostat.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
iostat -x 1
`iostat -x 1` provides extended disk I/O statistics, including `%util` (percentage of time the device was busy servicing requests) and `await` (average time for I/O operations). These metrics directly indicate disk bottlenecks and I/O wait issues. `iotop -o` displays only processes that are currently performing I/O operations, allowing the administrator to identify which specific processes are causing disk contention.
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.
iostat -x 1
Why this is correct
iostat -x shows extended I/O statistics per device.
Related concept
Read the scenario before looking for a memorised answer.
iotop -o
Why this is correct
iotop -o shows only processes with I/O activity.
Related concept
Read the scenario before looking for a memorised answer.
vmstat 1
Why it's wrong here
vmstat shows system summary, not per-process I/O.
sar -b 1
Why it's wrong here
sar -b shows I/O statistics but requires sysstat package and data collection.
dstat --disk-util
Why it's wrong here
dstat can show disk utilization, but not as detailed as iostat.
Common exam traps
The trap here is that candidates often choose `vmstat 1` because it shows the `wa` column, but they overlook that it does not provide per-disk or per-process granularity needed to identify the specific source of I/O wait.
Trap categories for this question
Command / output trap
vmstat shows system summary, not per-process I/O.
Detailed technical explanation
`iostat -x` reads from `/proc/diskstats` to calculate extended metrics like `avgqu-sz` (average queue length) and `svctm` (average service time). A high `%util` (near 100%) indicates the disk is saturated, but note that modern SSDs can handle multiple concurrent I/Os, so `%util` may not always reflect true saturation; `await` and `avgqu-sz` are more reliable for SSDs. `iotop -o` uses kernel accounting via `CONFIG_TASK_DELAY_ACCT` and `CONFIG_TASK_IO_ACCOUNTING` to track per-process I/O, which requires root privileges and kernel support.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the XK0-005 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: iostat -x 1 — `iostat -x 1` provides extended disk I/O statistics, including `%util` (percentage of time the device was busy servicing requests) and `await` (average time for I/O operations). These metrics directly indicate disk bottlenecks and I/O wait issues. `iotop -o` displays only processes that are currently performing I/O operations, allowing the administrator to identify which specific processes are causing disk contention.
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 11, 2026
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