Is there a list of what can be monitored by Icinga with out the agent and with the agent? I want to see what’s available and compare it against what’s available with Micro Focus SiteScope.
Icinga relies on check plugins which can check nearly anything, from a typical server as an agent, to network hardware to even an IoT enabled device, like your washing machine.
In case there’s no plugin available, and a daemon or script fires events, such can be passed in as external check result via the REST API as well.
That being said, a list and comparison with other tools is quite hard. I would focus on the other things available - dashboards, reporting, visualization (maps, metrics, etc.), integration with log event management tools, automated deployments, etc.
Sadly the Icinga monitoring capabilities can not be summed up in a simple document because it is limited by the imagination and the coding capabilities of the community.
To get a measure of the things Icinga can do, go to https://exchange.icinga.com/, and see what is available.
to try and simplify it, i can say this : if it has a port , it can be monitored without an agent.
if it is internal to the OS, you may need an agent ( but we do consider SSH as an agent for that purpose) , your call.