This LPIC-1 practice question tests your understanding of shells, scripting and data management. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 administrator wants to monitor a log file in real-time for lines containing 'ERROR' and write them to a separate file. Which command combination is most appropriate?
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.
less logfile
Why wrong: less is a pager, does not write to file.
tail -f logfile | grep 'ERROR' > error.log
tail -f provides real-time output, grep filters.
vi logfile
Why wrong: vi is an editor, not for real-time monitoring.
cat logfile | grep 'ERROR' > error.log
Why wrong: cat reads once, not real-time.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
tail -f logfile | grep 'ERROR' > error.log
Option A is correct: tail -f follows the file and grep filters lines. Option B uses cat which does not monitor live. Option C is a pager. Option D is a text editor.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
less logfile
Why it's wrong here
less is a pager, does not write to file.
tail -f logfile | grep 'ERROR' > error.log
Why this is correct
tail -f provides real-time output, grep filters.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
vi logfile
Why it's wrong here
vi is an editor, not for real-time monitoring.
cat logfile | grep 'ERROR' > error.log
Why it's wrong here
cat reads once, not real-time.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related LPIC-1 NAT questions on configuration and troubleshooting.
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FAQ
Shells, Scripting and Data Management — This question tests Shells, Scripting and Data Management — Static NAT maps one inside address to one outside address..
The correct answer is: tail -f logfile | grep 'ERROR' > error.log — Option A is correct: tail -f follows the file and grep filters lines. Option B uses cat which does not monitor live. Option C is a pager. Option D is a text editor.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related LPIC-1 NAT questions on configuration and troubleshooting.
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.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
This LPIC-1 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-1 exam.
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