XK0-006 Troubleshooting Practice Question
A Linux system is running slowly with high I/O wait as shown by vmstat. To investigate the I/O activity of a specific process that is suspected of causing the bottleneck, which of the following commands would be used to trace its system calls related to I/O?
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
✓
strace -p <pid>
The 'wa' in vmstat indicates CPU time spent waiting for I/O. To examine what I/O operations a particular process is performing, strace can be used to trace system calls such as read, write, and ioctl. By attaching to the process with strace -p <pid>, the administrator can see the I/O calls being made in real time. iostat provides aggregated per-device statistics, not per-process details. dmesg shows kernel messages, which may contain I/O errors but not process-level I/O patterns. free displays memory usage and is unrelated to I/O tracing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
iostat -x 1
Why it's wrong here
iostat shows aggregate disk stats, not per-process.
- ✓
strace -p <pid>
Why this is correct
strace traces system calls of a process, including I/O calls like read/write.
- ✗
dmesg | tail
Why it's wrong here
dmesg shows kernel messages, not per-process I/O.
- ✗
free -h
Why it's wrong here
free shows memory, not I/O.
Go deeper
Related to this question
Learn chapter
Linux Fundamentals and History
Key term
Process
In IT service management, a process is a structured set of activities designed to accomplish a specific objective, such as managing incidents or changes, by transforming inputs into defined outputs.
Key term
dmesg
dmesg is a Linux command that displays messages from the kernel ring buffer, used to diagnose hardware and boot issues.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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