This LFCS practice question tests your understanding of operation of running systems. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 system running RHEL 8 experiences intermittent crashes. After reboot, 'journalctl -p err -b -1' outputs: 'PID 1234 (myapp) ended due to signal: KILL'. Which diagnostic step should the administrator perform next?
Review logrotate configuration for myapp logs.
Why wrong: Unrelated to the kill signal.
Run strace to capture system calls of myapp before restarting.
Why wrong: Cannot trace after process killed.
Enable core dumps and reproduce issue.
Why wrong: Helpful but not immediate next step.
Check journalctl for 'oom-kill' entries or use 'dmesg | grep -i oom'.
Identifies if out-of-memory killer caused the kill.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Check journalctl for 'oom-kill' entries or use 'dmesg | grep -i oom'.
The 'PID ended due to signal: KILL' message indicates the process was terminated by a SIGKILL (signal 9), which is commonly sent by the Out-Of-Memory (OOM) killer when the system runs low on memory. Checking journalctl for 'oom-kill' entries or using 'dmesg | grep -i oom' directly confirms whether the OOM killer was responsible, making D the correct next diagnostic step.
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.
Review logrotate configuration for myapp logs.
Why it's wrong here
Unrelated to the kill signal.
Run strace to capture system calls of myapp before restarting.
Why it's wrong here
Cannot trace after process killed.
Enable core dumps and reproduce issue.
Why it's wrong here
Helpful but not immediate next step.
Check journalctl for 'oom-kill' entries or use 'dmesg | grep -i oom'.
Why this is correct
Identifies if out-of-memory killer caused the kill.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates may confuse 'signal: KILL' with a manual kill command or a segmentation fault, leading them to choose core dumps (C) or strace (B), when the specific signal name 'KILL' (SIGKILL) points directly to the OOM killer or an explicit kill -9, and the OOM killer is the most common cause in intermittent crash scenarios.
Detailed technical explanation
The OOM killer in Linux uses a heuristic called 'oom_badness' to select a process to kill, based on factors like memory usage, process priority (oom_score_adj), and runtime. When the kernel detects a memory shortage, it invokes the OOM killer, which sends an unblockable SIGKILL (signal 9) to the chosen process. The 'journalctl -p err -b -1' command shows errors from the previous boot, and the 'KILL' signal in the log is a strong indicator of OOM activity, which can be verified by searching for 'oom-kill' in the kernel ring buffer via dmesg or journalctl.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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FAQ
Operation of Running Systems — This question tests Operation of Running Systems — Read the scenario before looking for a memorised answer..
The correct answer is: Check journalctl for 'oom-kill' entries or use 'dmesg | grep -i oom'. — The 'PID ended due to signal: KILL' message indicates the process was terminated by a SIGKILL (signal 9), which is commonly sent by the Out-Of-Memory (OOM) killer when the system runs low on memory. Checking journalctl for 'oom-kill' entries or using 'dmesg | grep -i oom' directly confirms whether the OOM killer was responsible, making D the correct next diagnostic step.
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 25, 2026
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