CheckMK is a great monitoring solution that can be used for free if you want to know what is going on with e.g. your Puppet server or your own Mail- and Cloud server.

If you want to use it for free, there are two different options. Either you use CheckMK Raw, which does not offer all features of the Enterprise Edition, or you use CheckMK Free which offers all features but is limited to 10 hosts. For me the limit of 10 hosts is not enough so I use CheckMK Raw for my needs. For a comparison of the available editions you should check out the official site.

The documentation of CheckMK is superb and I really urge you to use it. Here I just want to describe some specialties which are either not part of CheckMK, or where the documentation is not 100% clear.

If you are using Puppet for configuration and state management, and you are not using the Enterprise edition, it is quite difficult to have an overview of the state of your Puppet runs (especially the failing ones).

Luckily, there is this excellent plugin for CheckMK from Allan Good, which makes it possible to monitor your Puppet clients and their status.

His Plugin is based on either the Puppet Enterprise Edition, or another distribution than Debian however, so some slight modifications are necessary.