The correct answer is to clear log files using the 'clear log messages' command, as this immediately frees disk space in the /var partition without disrupting device operation. This command truncates the active log files—such as messages and interactive-commands—while leaving the directory structure intact, allowing logging to continue normally. On the JNCIA-Junos exam, this scenario tests your understanding of Junos operational commands and disk management, often appearing as a trap where candidates might incorrectly choose to reboot or delete files manually. A common memory tip is to remember that "clear" in Junos means to empty, not delete, so the logs remain as empty files ready for new data. For quick recall, think: "Clear logs, not delete—space freed, logs still neat."
JNCIA-JUNOS Junos OS Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos os fundamentals. 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 technician notices that the /var partition on a Junos device is 95% full. Which action will immediately free up disk space without affecting device operation?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "immediately / without restart"
Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Clear log files using 'clear log messages'
Option D is correct because the 'clear log messages' command immediately removes the contents of the active log files (e.g., messages, interactive-commands) without requiring a reboot or affecting running processes. This directly frees up space in /var/log, which is a primary consumer of the /var partition, while leaving the directory structure intact so logging continues normally.
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.
✗
Delete unused software packages using 'request system software delete'
Why it's wrong here
Deleting packages frees space but requires a commitment; it's not immediate and may need a reboot.
✗
Reboot the device
Why it's wrong here
Rebooting does not free space; it may cause temporary disruption.
✗
Remove the /var/log directory
Why it's wrong here
Removing system directories would break logging and may cause system instability.
✓
Clear log files using 'clear log messages'
Why this is correct
Clearing log files immediately frees space in /var with no impact on operations.
Clue confirmation
The clue word "immediately / without restart" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think rebooting (Option B) clears all temporary files and logs, but Junos does not automatically delete persistent log files on reboot; only volatile /tmp is cleared, so /var remains full.
Detailed technical explanation
How to think about this question
Under the hood, Junos uses a circular logging mechanism where log files are rotated based on size or time, but old rotated logs (e.g., messages.0.gz) accumulate in /var/log until manually cleaned or pruned by a configured retention policy. The 'clear log messages' command truncates the active log file to zero bytes and removes all rotated log files for that facility, instantly reclaiming space without restarting the syslog daemon. In real-world scenarios, a common oversight is forgetting to set 'log-rotate-frequency' or 'max-log-size' in the syslog configuration, leading to unexpected /var partition exhaustion during high-traffic events.
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 JNCIA-JUNOS 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.
Junos OS Fundamentals — This question tests Junos OS Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Clear log files using 'clear log messages' — Option D is correct because the 'clear log messages' command immediately removes the contents of the active log files (e.g., messages, interactive-commands) without requiring a reboot or affecting running processes. This directly frees up space in /var/log, which is a primary consumer of the /var partition, while leaving the directory structure intact so logging continues normally.
What should I do if I get this JNCIA-JUNOS 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: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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