The correct command is `tar -xzf /backup/logs.tar.gz --to-stdout var/log/app.log > /var/log/app.log`. This works because the `-xzf` flags extract from a compressed archive, but by specifying the exact file path (without the leading slash) and using `--to-stdout`, the command sends only that file’s content to standard output instead of decompressing the entire archive to disk. The redirection operator then recreates the file at its original location. On the LFCS exam, this tests your understanding of selective extraction and stream redirection—a common trap is attempting `tar -xzf` without `--to-stdout`, which would still extract the single file but could overwrite other files if the archive contains multiple entries. Remember that `tar` strips leading slashes by default, so the path inside the archive is `var/log/app.log`, not `/var/log/app.log`. Memory tip: think “pipe the one file out, don’t unpack the whole house.”
LFCS Essential Commands Practice Question
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.
A developer accidentally deleted a critical file /var/log/app.log. The system administrator knows that the file was recently backed up using a cron job that runs 'tar -czf /backup/logs.tar.gz /var/log/'. Which command should the administrator use to restore the file from the backup without extracting the entire archive?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
tar -xzf /backup/logs.tar.gz --to-stdout var/log/app.log > /var/log/app.log
Option C is correct because `tar -xzf` extracts the specified file (`var/log/app.log`) from the compressed archive and `--to-stdout` sends its content to standard output, which is then redirected to recreate the file at `/var/log/app.log`. This restores the single file without extracting the entire archive, matching the requirement precisely.
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.
✗
tar -xf /backup/logs.tar.gz var/log/app.log
Why it's wrong here
This extracts all files, not just the single file.
✗
tar -tf /backup/logs.tar.gz | grep app.log
Why it's wrong here
This only lists the file, does not extract it.
✓
tar -xzf /backup/logs.tar.gz --to-stdout var/log/app.log > /var/log/app.log
Why this is correct
Correctly extracts the single file to stdout and redirects to restore it.
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.
cp does not work with archives; this syntax is invalid.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume `tar -xf` works with `.tar.gz` files without the `-z` flag, or that `cp` can directly reference files inside a tar archive using a colon syntax, which is not supported by the standard `cp` command.
Detailed technical explanation
How to think about this question
The `--to-stdout` option (or `-O` shorthand) redirects the extracted file data to stdout instead of writing it to disk, allowing redirection to a specific path. This is particularly useful when the archive was created with an absolute or relative path that differs from the desired restore location, or when you need to avoid overwriting other files in the archive. Under the hood, tar reads the archive sequentially, finds the matching member by path, decompresses it on the fly (with `-z`), and writes the data to stdout.
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 LFCS 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.
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: tar -xzf /backup/logs.tar.gz --to-stdout var/log/app.log > /var/log/app.log — Option C is correct because `tar -xzf` extracts the specified file (`var/log/app.log`) from the compressed archive and `--to-stdout` sends its content to standard output, which is then redirected to recreate the file at `/var/log/app.log`. This restores the single file without extracting the entire archive, matching the requirement precisely.
What should I do if I get this LFCS 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: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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