This LPIC-2 practice question tests your understanding of linux kernel and system startup. 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 limit the size of the kernel ring buffer to prevent memory overflow. Which kernel boot parameter should be used?
log_buf_len
log_buf_len sets the kernel log buffer size (e.g., log_buf_len=4M).
log_size
Why wrong: This is not a valid kernel parameter.
kernel.log.size
Why wrong: This is not a kernel parameter; log size is set via log_buf_len.
dmesg_size
Why wrong: This is not a valid kernel parameter.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
log_buf_len
Option A is correct because `log_buf_len` is the kernel boot parameter that explicitly sets the size of the kernel ring buffer (dmesg buffer). By specifying a value (e.g., `log_buf_len=4M`), the administrator can increase or limit the buffer size to prevent memory overflow when a large volume of kernel messages is generated.
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.
log_buf_len
Why this is correct
log_buf_len sets the kernel log buffer size (e.g., log_buf_len=4M).
Related concept
Read the scenario before looking for a memorised answer.
log_size
Why it's wrong here
This is not a valid kernel parameter.
kernel.log.size
Why it's wrong here
This is not a kernel parameter; log size is set via log_buf_len.
dmesg_size
Why it's wrong here
This is not a valid kernel parameter.
Common exam traps
The trap here is that candidates may confuse kernel boot parameters with sysctl or configuration file settings, leading them to pick plausible-sounding but nonexistent options like `log_size` or `dmesg_size` instead of the correct `log_buf_len`.
Detailed technical explanation
The kernel ring buffer is a fixed-size circular buffer in kernel memory that stores log messages from `printk()`. The `log_buf_len` parameter accepts values in bytes or with suffixes like `K`, `M`, or `G` (e.g., `log_buf_len=2M`). If the buffer overflows, older messages are overwritten, which can cause loss of critical debugging information; setting an appropriate size is especially important on systems with verbose kernel logging or during early boot stages before userspace logging daemons start.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the LPIC-2 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Linux Kernel and System Startup — This question tests Linux Kernel and System Startup — Read the scenario before looking for a memorised answer..
The correct answer is: log_buf_len — Option A is correct because `log_buf_len` is the kernel boot parameter that explicitly sets the size of the kernel ring buffer (dmesg buffer). By specifying a value (e.g., `log_buf_len=4M`), the administrator can increase or limit the buffer size to prevent memory overflow when a large volume of kernel messages is generated.
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
This LPIC-2 practice question is part of Courseiva's free LPI 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 LPIC-2 exam.
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