Previously we only added the Check_MK service if the host had passive services.
We now add it always, unless the host is a ping-only host.
Originally the main job of the Check_MK service was to trigger the passive services, so it was not needed for hosts without them.
However, for a while now the service also reports the success of the data sources, which may be relevant for hosts without passive services as well.
In particular, a failing data source may be the reason why we don't see passive services in the first place.
For example there are special agents that only create services on piggybacked hosts.
If you configure such an agent on a dedicated host, you would not have seen the status of the agent at all.
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