It's beyond the scope of this wiki to fully describe what OMD is, except to say that it is a bundling of open source monitoring tools built around Nagios. It includes such packages as Nagios, Nagios plugins, Check_MK, mk_livestatus, mk_multisite, pnp4nagios. Effectively using OMD requires an administrator to have prior knowledge of these tools. Much documentation can be found here:

Nagios Docs http://nagios.sourceforge.net/docs/3_0/toc.html

Check_MK Docs http://mathias-kettner.de/checkmk.html

Check_MK Variable Reference http://mathias-kettner.de/checkmk_configvars.html

* The OMD source can be freely downloaded via git.

omd.git

* Compile from source:

git clone http://git.mathias-kettner.de/omd.git
cd omd
./configure
make
make rpm