JN0-106 Junos OS Fundamentals Practice Question
During a maintenance window, an engineer needs to apply a series of configuration changes that are stored in a text file. Which command sequence should be used to load and apply the changes from the file?
⚠ Common exam trap
It's easy for candidates to confuse 'load merge' with 'load override' or 'load patch', not realizing that 'load merge' is the correct command for applying incremental changes from a standard configuration text file, while 'load override' wipes the entire configuration and 'load patch' requires a specific diff format.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
configure; load merge /var/tmp/changes.txt; commit
The engineer needs to enter configuration mode (configure) and then use the 'load merge' command to merge the contents of the text file into the candidate configuration without replacing the entire configuration. The 'commit' command then activates the changes. This is the standard Junos workflow for applying incremental changes from a file.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
request system configuration rescue save
Why it's wrong here
This command saves the current active configuration as the rescue configuration, which is used for recovery from commit errors or system instabilities. It does not load or merge any changes from an external file; instead, it overwrites the rescue configuration with the running configuration. Therefore, executing it would not apply /var/tmp/changes.txt, and it could unintentionally replace a previously saved rescue configuration, undermining its purpose.
- ✗
load override /var/tmp/changes.txt; commit
Why it's wrong here
The load override command replaces the entire candidate configuration with the contents of the specified file. Since changes.txt presumably contains only the incremental modifications and not the full device configuration, all existing statements not present in the file would be removed. The subsequent commit would then activate this stripped-down configuration, deleting critical settings like interfaces, routing protocols, or security policies, and potentially causing a major outage. This approach is too destructive for applying a maintenance change; a merge is required.
- ✗
configure; load patch /var/tmp/changes.txt; commit
Why it's wrong here
The load patch command is intended specifically for applying an XML patch file, which represents configuration differences in a structured XML format (e.g., generated with `show configuration | display patch`). It is not designed for plain-text configuration snippets or 'set' command lists. If changes.txt is a standard text configuration, load patch will either raise a syntax error or apply the patch incorrectly because the file does not conform to the expected XML patch schema. Thus, this command is unsuitable for the task.
- ✓
configure; load merge /var/tmp/changes.txt; commit
Why this is correct
This sequence correctly applies the configuration changes by merging the contents of changes.txt into the current candidate configuration. The load merge command overlays the file's statements onto the existing configuration, adding new statements and updating existing ones while leaving all unrelated configuration untouched. The commit then activates the candidate configuration, making the changes effective. This is the safest and most precise way to apply an incremental change during a maintenance window, as it avoids deleting any existing configuration.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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