- A
Check dmesg for each module load error and recompile modules one by one
Why wrong: While possible, it is inefficient and does not provide a comprehensive list of missing symbols.
- B
Rename the missing symbols in the source code to match the new kernel's exported symbols
Why wrong: Renaming may not fix the underlying API changes; the module needs to be updated to use the new symbols correctly.
- C
Run 'modprobe --dump-modversions mymodule.ko' and compare with 'cat /proc/kallsyms' to identify mismatches
This method systematically shows which symbols the module requires and whether they are present in the running kernel.
- D
Use 'nm mymodule.ko' to list all symbols and manually compare with the kernel's symbol table
Why wrong: Manual comparison is tedious and error-prone; automated tools are better.
LPIC-2 Linux Kernel and System Startup Practice Question
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.
A Linux system administrator is tasked with upgrading the kernel on a server running a custom compiled kernel (version 4.19) with many in-house modules. The new kernel (5.10) has significant changes, including a different API for some module functions. After compiling the new kernel and the modules, the system boots but some modules fail to load with 'Unknown symbol' errors. The administrator needs to identify which symbols are missing and fix the modules. Which of the following is the most effective approach?
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
Run 'modprobe --dump-modversions mymodule.ko' and compare with 'cat /proc/kallsyms' to identify mismatches
Option C is correct because `modprobe --dump-modversions mymodule.ko` displays the symbol version (CRC) checksums for each symbol the module uses, and comparing these with `/proc/kallsyms` (which lists all symbols exported by the running kernel along with their CRC values) directly pinpoints which symbols have mismatched versions. This is the most efficient method to identify 'Unknown symbol' errors caused by API changes between kernel 4.19 and 5.10, as it reveals exactly which symbols need updating in the module source code.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Check dmesg for each module load error and recompile modules one by one
Why it's wrong here
While possible, it is inefficient and does not provide a comprehensive list of missing symbols.
- ✗
Rename the missing symbols in the source code to match the new kernel's exported symbols
Why it's wrong here
Renaming may not fix the underlying API changes; the module needs to be updated to use the new symbols correctly.
- ✓
Run 'modprobe --dump-modversions mymodule.ko' and compare with 'cat /proc/kallsyms' to identify mismatches
Why this is correct
This method systematically shows which symbols the module requires and whether they are present in the running kernel.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use 'nm mymodule.ko' to list all symbols and manually compare with the kernel's symbol table
Why it's wrong here
Manual comparison is tedious and error-prone; automated tools are better.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume symbol name matching is sufficient (Option D) or that recompiling blindly (Option A) will fix the issue, when in fact the kernel's symbol versioning (CRC) mechanism is what causes the failure, and only a version-aware comparison can diagnose it correctly.
Detailed technical explanation
How to think about this question
The 'Unknown symbol' error occurs because the kernel's module loader uses a version magic (vermagic) and per-symbol CRC checksums to ensure binary compatibility. When the kernel API changes, the CRC values for exported symbols change, even if the symbol names remain the same. `modprobe --dump-modversions` extracts these CRCs from the module's .modinfo section, while `/proc/kallsyms` shows the kernel's current CRCs; comparing them reveals exactly which symbols need their module code updated to match the new kernel's function signatures.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this LPIC-2 question test?
Linux Kernel and System Startup — This question tests Linux Kernel and System Startup — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Run 'modprobe --dump-modversions mymodule.ko' and compare with 'cat /proc/kallsyms' to identify mismatches — Option C is correct because `modprobe --dump-modversions mymodule.ko` displays the symbol version (CRC) checksums for each symbol the module uses, and comparing these with `/proc/kallsyms` (which lists all symbols exported by the running kernel along with their CRC values) directly pinpoints which symbols have mismatched versions. This is the most efficient method to identify 'Unknown symbol' errors caused by API changes between kernel 4.19 and 5.10, as it reveals exactly which symbols need updating in the module source code.
What should I do if I get this LPIC-2 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 25, 2026
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