Quick Answer
The answer is the `show system storage` command, which is the correct way to check disk space usage on a Junos device. This command works because it queries the filesystem table directly, displaying total, used, and available space for each mounted partition—including critical directories like `/var`—along with the percentage of utilization. On the JNCIA-Junos exam, this question tests your ability to monitor operational resources, often appearing as a straightforward command-identification item where a common trap is confusing it with `show system statistics` or `show file list`. Remember that `show system storage` is the Junos equivalent of `df -h` on Linux, making it your go-to for disk usage checks. A simple memory tip: “Storage shows space,” so when you need to see how full your disk is, think of the word “storage” in the command.
This JNCIA-JUNOS practice question tests your understanding of operational monitoring and maintenance. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 Juniper device is running out of disk space on the /var partition. Which command can be used to check disk usage?
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.
show system storage
Displays filesystem usage including /var.
show system disk-space
Why wrong: Not a valid Junos command.
show system memory
Why wrong: Shows memory usage, not disk.
show system resource
Why wrong: Not a standard command for disk.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
show system storage
The correct command to check disk usage on a Juniper device is 'show system storage'. This command displays detailed information about disk partitions, including total, used, and available space, as well as the percentage of usage for each mounted filesystem, such as /var. It is the standard operational mode command for monitoring storage utilization in Junos OS.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
show system storage
Why this is correct
Displays filesystem usage including /var.
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.
show system disk-space
Why it's wrong here
Not a valid Junos command.
show system memory
Why it's wrong here
Shows memory usage, not disk.
show system resource
Why it's wrong here
Not a standard command for disk.
Common exam traps
The trap here is that candidates familiar with other operating systems might expect a command like 'show system disk-space' or confuse memory with storage, but Junos uses the specific phrase 'storage' for disk usage monitoring.
Trap categories for this question
Command / output trap
Not a valid Junos command.
Detailed technical explanation
The 'show system storage' command queries the filesystem statistics from the kernel, similar to the Unix 'df -h' command, and presents them in a Junos-specific format. It is particularly useful for monitoring the /var partition, which stores logs, configuration backups, and core files, and can fill up quickly in high-traffic environments. A real-world scenario is when a syslog flood or excessive core dumps consume /var space, causing operational issues like failed commits or inability to write logs.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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
Operational Monitoring and Maintenance — This question tests Operational Monitoring and Maintenance — Read the scenario before looking for a memorised answer..
The correct answer is: show system storage — The correct command to check disk usage on a Juniper device is 'show system storage'. This command displays detailed information about disk partitions, including total, used, and available space, as well as the percentage of usage for each mounted filesystem, such as /var. It is the standard operational mode command for monitoring storage utilization in Junos OS.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This JNCIA-JUNOS practice question is part of Courseiva's free Juniper Networks 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 JNCIA-JUNOS exam.
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