This LFCS practice question tests your understanding of essential commands. 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.
An administrator wants to terminate a process with PID 1234 and all its child processes. Which command should be used?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
pkill -P 1234
Why wrong: Kills children only, not the parent.
kill -9 -1234
Sends SIGKILL to the entire process group.
kill -15 1234
Why wrong: Sends SIGTERM, but still only to the parent.
kill -9 1234
Why wrong: Only kills the parent process.
Answer choices
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
Option B is correct because the `kill` command with a negative PID (e.g., `kill -9 -1234`) sends the signal to the process group identified by the absolute value of the PID. Since process group IDs typically equal the PID of the group leader, using `-1234` targets the entire process group, terminating PID 1234 and all its child processes. The `-9` (SIGKILL) ensures immediate termination without cleanup.
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.
pkill -P 1234
Why it's wrong here
Kills children only, not the parent.
kill -9 -1234
Why this is correct
Sends SIGKILL to the entire process group.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
kill -15 1234
Why it's wrong here
Sends SIGTERM, but still only to the parent.
kill -9 1234
Why it's wrong here
Only kills the parent process.
Common exam traps
The trap here is that candidates often assume `kill -9 1234` terminates the entire process tree, but it only kills the specified process, leaving child processes orphaned; the negative PID syntax is the correct way to target a process group.
Detailed technical explanation
In Linux, each process belongs to a process group, and the process group ID (PGID) is often the PID of the group leader. Using a negative PID with `kill` sends the signal to all processes in that process group, which is a POSIX-defined behavior (see `kill(2)`). This is useful in scenarios like terminating a runaway script that spawns multiple subshells, ensuring no orphaned processes remain.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
The correct answer is: kill -9 -1234 — Option B is correct because the `kill` command with a negative PID (e.g., `kill -9 -1234`) sends the signal to the process group identified by the absolute value of the PID. Since process group IDs typically equal the PID of the group leader, using `-1234` targets the entire process group, terminating PID 1234 and all its child processes. The `-9` (SIGKILL) ensures immediate termination without cleanup.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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.
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