LFCS Operation of Running Systems Practice Question
A system administrator notices that a process is consuming 100% CPU and is unresponsive. Which command should be used to immediately stop the process if the PID is 2345?
⚠ Common exam trap
Many exam-takers choose `kill -15` (SIGTERM) thinking it is safer, but the question explicitly requires immediate stoppage of an unresponsive process, where only SIGKILL guarantees termination.
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
✓
kill -9 2345
`kill -9 2345` sends the SIGKILL signal (signal 9) to process ID 2345, which immediately terminates the process without allowing it to clean up or ignore the signal. This is the appropriate action for an unresponsive process consuming 100% CPU, as SIGKILL cannot be caught or blocked by the process.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
kill -9 2345
Why this is correct
Sending SIGKILL (signal 9) to PID 2345 forces immediate termination at the kernel level, since the process cannot catch, block or ignore this signal. This satisfies the stem's requirement to stop an unresponsive process immediately, whereas gentler signals such as SIGTERM may be ignored by a hung process.
- ✗
pkill -9 processname
Why it's wrong here
pkill matches by process name, not the given PID 2345, so it may signal unrelated processes sharing that name or none at all. It suits terminating every instance of a named program, for example all stray worker processes, rather than one identified PID.
- ✗
systemctl stop processname
Why it's wrong here
systemctl stop targets a systemd unit name, not an arbitrary PID, so it cannot address PID 2345 directly and fails if the process is not a managed service. It is correct when stopping a known unit such as nginx.service through systemd.
- ✗
kill -15 2345
Why it's wrong here
SIGTERM (15) requests graceful termination, which an unresponsive process consuming 100% CPU may ignore, so it will not stop immediately. Graceful signals are tempting for safe shutdowns, but SIGKILL (9) is required here because it cannot be caught or ignored, guaranteeing immediate termination of PID 2345.
Go deeper
Related to this question
About these practice questions
This LFCS question is part of Courseiva's 406-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.