Hi
yes you can modify the behavior of device-template interactions w/ devices.
If you look in the documentation :: e.g. "NSO 4.7.3.2 Getting Started Guide" on Chapter 3 - NSO Basics
and page 19 where it describes "Device Templates" you will find a discussion about "tags"...
Tags are very important to XML and control its behavior. NSO templates assume tags="merge" as the default behavior.
from the document
"""
Another important question is how to control if the template shall merge the list or replace the list. This is managed via "tags". The default behavior of templates is to merge the configuration. Tags can be inserted at any point in the template. Tag values are merge, replace, delete, create and nocreate.
"""
and later...
"""
Any existing values in the list are replaced in this case. The following tags are available:
* merge (default): the template changes will be merged with the existing template
* replace: the template configuration will be replaced by the new configuration
* create: the template will create those nodes which does not exist. If a node already exists this will
result in an error.
* nocreate: the merge will only affect configuration items that already exist in the template. It will never create the configuration with this tag, or any associated commands inside it. It will only modify existing configuration structures.
* delete: delete anything from this point
"""
What you want is (if i understand your question) is to wrap the ntp section with tags="replace" for that entire section. Be sure to give all the relevant NTP servers (I assume you are also using variable substitution in your device-template).
this will then ensure that _THESE_ and ONLY THESE ntp servers exist on the device. (if there are extra ones they will be remove; if there are missing ones they will be added).
How do you add these tags? The documentation also describes how to add them from NSO CLI, but personally, i find it cumbersome to work this way - so - i typically save the device-template as an XML file, then edit the file (with vi for example), or your favorite editor), and then "load merge" the edited file to replace the old one...
to save it you can "pipe" the file
show xxxxx | display xml | save foofile.xml
then edit foofile.xml, add your tag, and then load-merge the file
you'll probably end up with something like...
<config>
<ntp xmlns="http://tail-f.com/ned/cisco-ios-xr">
<server tags="replace">
<server-list>
etc.
etc.
best,
gregg
