The answer is using `dd if=/dev/sda of=/mnt/evidence/image.dd bs=4M` because it provides a bit-for-bit forensic image of the entire disk from a live Linux server without requiring a shutdown. This command directly addresses the need for a linux live forensic disk image dd command by setting a 4M block size, which dramatically improves acquisition speed on a running system while still producing a forensically sound copy. On the Computer Hacking Forensic Investigator CHFI exam, this question tests your understanding that `conv=noerror,sync` is unnecessary for a healthy live disk and can actually mask read errors, making the simpler dd with a larger block size the best practice for live acquisition. A common trap is choosing options with error-handling flags that compromise forensic integrity. Remember the memory tip: "Big blocks, no sync—live disks don't need the trick."
CHFI Incident Response and First Responder Skills Practice Question
This CHFI practice question tests your understanding of incident response and first responder skills. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
During an incident response, a first responder needs to collect evidence from a Linux server that is still running. The server has sensitive data and cannot be shut down. Which technique is BEST for acquiring a forensic image of the hard disk?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use dd if=/dev/sda of=/mnt/evidence/image.dd bs=4M
Option B is correct because it uses dd with a 4M block size, which improves acquisition speed while still producing a bit-for-bit forensic image of the entire disk (/dev/sda). The conv=noerror,sync option in A is unnecessary for a live acquisition from a healthy disk and can mask read errors, while B's larger block size is more efficient for imaging a running system without shutdown.
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.
✗
Use dd if=/dev/sda of=/mnt/evidence/image.dd conv=noerror,sync
Why it's wrong here
While noerror,sync is useful for skipping bad sectors, it may alter the image; standard practice is to use dd without such flags.
✓
Use dd if=/dev/sda of=/mnt/evidence/image.dd bs=4M
Why this is correct
dd copying the entire disk (/dev/sda) creates a complete forensic image.
Clue confirmation
The clue words "best", "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use dd if=/dev/mapper/root of=/mnt/evidence/image.dd
Why it's wrong here
/dev/mapper/root captures only a logical volume, not the entire disk.
✗
Use dd if=/dev/sda1 of=/mnt/evidence/image.dd
Why it's wrong here
/dev/sda1 is a partition, not the full disk; missing partition table and other partitions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
EC-Council often tests the misconception that conv=noerror,sync is always required for forensic imaging, but in a live, healthy server scenario, it can introduce artifacts and is not the best practice.
Detailed technical explanation
How to think about this question
Under the hood, dd reads raw block devices in user-specified block sizes; a 4M block size reduces system call overhead and I/O wait, which is critical when imaging a live server to minimize performance impact and avoid data changes during acquisition. In real-world incident response, the first responder must balance speed with forensic soundness—using a larger block size (e.g., 4M or 64M) is standard practice for live Linux acquisitions, while conv=noerror,sync is reserved for damaged media to prevent the tool from stopping on errors.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CHFI question in full detail.
Incident Response and First Responder Skills — This question tests Incident Response and First Responder Skills — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use dd if=/dev/sda of=/mnt/evidence/image.dd bs=4M — Option B is correct because it uses dd with a 4M block size, which improves acquisition speed while still producing a bit-for-bit forensic image of the entire disk (/dev/sda). The conv=noerror,sync option in A is unnecessary for a live acquisition from a healthy disk and can mask read errors, while B's larger block size is more efficient for imaging a running system without shutdown.
What should I do if I get this CHFI question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best", "first". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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