LFCS Essential Commands Practice Question
Exhibit
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1234 99.5 0.2 12345 6789 pts/0 R 10:00 45:00 process_hog
Refer to the exhibit. The output of 'ps aux' shows a process named 'process_hog' with PID 1234 consuming 99.5% CPU. The process is stuck in an infinite loop and does not respond to SIGTERM. Which signal should be used to forcefully terminate it?
⚠ Common exam trap
In LFCS, the key distinction is between termination signals (SIGTERM, SIGKILL) and stop signals (SIGSTOP). SIGTERM allows graceful shutdown, but if ignored, SIGKILL is the only way to force termination. Some candidates incorrectly use SIGSTOP (pause) or confuse SIGTERM with a guaranteed kill.
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 1234
SIGKILL (signal 9) cannot be caught, blocked, or ignored by a process, making it the only reliable way to terminate a process that is stuck in an infinite loop and unresponsive to SIGTERM. Since the process does not respond to SIGTERM (signal 15), a forceful kill with kill -9 is necessary.
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 -2 1234
Why it's wrong here
Signal 2 is SIGINT, the interactive interrupt, which the stuck process ignores just as it ignores SIGTERM; only SIGKILL (9) cannot be caught or blocked. It is tempting because SIGINT terminates most foreground processes, and it is the correct choice when you want a graceful interrupt rather than an unconditional kill.
- ✓
kill -9 1234
Why this is correct
SIGKILL, signal 9, cannot be caught or ignored, so the kernel terminates the process immediately. SIGTERM is handled or blocked by the looping process, which is why it survived. kill -9 1234 forcefully ends it.
- ✗
kill -15 1234
Why it's wrong here
SIGTERM (15) is the graceful termination request the process is already ignoring, so resending it changes nothing. SIGKILL (9) cannot be caught or blocked and forcibly ends the process; SIGTERM would be correct for a process that shuts down cleanly on request.
- ✗
kill -19 1234
Why it's wrong here
Signal 19 is SIGSTOP, which suspends the process rather than terminating it, leaving PID 1234 alive and still holding resources. It is tempting because it forcibly halts execution; it would be correct when pausing a runaway job for inspection before resuming it with SIGCONT.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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