LibreNMS supports grouping your devices together in much the same way as you can configure alerts. This document will hopefully help you get started.
The rule is based on the MySQL structure your data is in. Such as tablename.columnname. If you already know the entity you want, you can browse around inside MySQL using
show tables and
As a working example and a common question, let's assume you want to group devices by hostname. If your hostname format is dcX.[devicetype].example.com. You would use the field
If you want to group them by device type, you would add a rule for routers of
If you want to group them by DC, you could use the rule
dc1\..*\.example\.com (Don't forget to escape periods in the regex)
You can create static groups (and convert dynamic groups to static) to put specific devices in a group. Just select static as the type and select the devices you want in the group.
You can now select this group from the Devices -> All Devices link in the navigation at the top. You can also use the group to map alert rules to by creating an alert mapping
Overview -> Alerts -> Rule Mapping.