Quick Answer
The answer is to use the show log messages command, along with show log dm and show log | match. The show log messages command is correct because it directly reads the /var/log/messages file, which is the primary system log file in Junos OS, capturing kernel messages, system startup events, and critical operational logs. On the JNCIA-Junos exam, this question tests your ability to recall the default log file and the commands that interact with it; a common trap is confusing the traceoptions logs in /var/log with the main system log, or forgetting that show log dm is a valid alias for the default messages file. To view system log messages effectively, remember that show log without a filename defaults to messages, and you can pipe any log output through | match to filter for specific events. A helpful memory tip is to think of "messages" as the master log—if you need to check system health or boot events, that is your go-to file.
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.
Which three commands can be used to view system log messages? (Choose three.)
show system syslog
Why wrong: Shows syslog configuration, not messages.
show log messages
Displays messages log file.
monitor start messages
Starts real-time monitoring of syslog messages.
show log dm
Displays the daemon messages log file.
tail -f /var/log/messages
Why wrong: Unix command, not available in Junos CLI (requires shell).
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 log messages
Option B is correct because the 'show log messages' command displays the contents of the /var/log/messages file, which is the primary system log file on Junos OS. This file contains kernel messages, system startup events, and other critical operational logs, making it a standard way to view system log messages.
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 syslog
Why it's wrong here
Shows syslog configuration, not messages.
show log messages
Why this is correct
Displays messages log file.
Related concept
Read the scenario before looking for a memorised answer.
monitor start messages
Why this is correct
Starts real-time monitoring of syslog messages.
Related concept
Read the scenario before looking for a memorised answer.
show log dm
Why this is correct
Displays the daemon messages log file.
Related concept
Read the scenario before looking for a memorised answer.
tail -f /var/log/messages
Why it's wrong here
Unix command, not available in Junos CLI (requires shell).
Common exam traps
The trap here is that candidates may confuse the Unix shell command 'tail -f /var/log/messages' with a valid Junos CLI command, or assume 'show system syslog' is a valid operational command when it is actually a configuration context command.
Trap categories for this question
Command / output trap
Shows syslog configuration, not messages.
Detailed technical explanation
Junos OS stores log messages in files under /var/log/, with the default system log file being 'messages'. The 'show log' command reads these files directly, while 'monitor start' provides a real-time tail-like view by streaming new log entries to the terminal. The 'dm' file is a separate log for chassis daemon messages, often used for debugging hardware-related issues. Understanding the distinction between viewing static logs and monitoring live logs is crucial for operational troubleshooting.
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
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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 log messages — Option B is correct because the 'show log messages' command displays the contents of the /var/log/messages file, which is the primary system log file on Junos OS. This file contains kernel messages, system startup events, and other critical operational logs, making it a standard way to view system log messages.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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