What is the Open Monitoring Distribution?

One of the great advantages of OMD is that all of the important components can be installed with an RPM/DEB package, and dependencies on OS packages are also taken into account. This means that with OMD, monitoring is ready for use immediately after installation.

An OMD-based installation has the following features:

• the ability to run multiple sites in parallel,
• the possibility to do so with differing versions of the monitoring software,
• an intelligent and convenient upgrade mechanism,
• uniform file paths – regardless of the Linux platform used,
• a very easy installation – without dependency on third party software – and
• a perfect pre-configuration of all components.

A major advantage of OMD is that it can run any number of monitoring sites on one server without virtualization. Each of these sites is a closed monitoring system that runs separately from the others. However, all sites can be administered centrally and thus, for example, updates can be rolled out specifically to the desired instance. A further advantage of OMD's structure is that all of a site's data is located in a single directory, which makes data backup much easier.

The operation of several sites on a single server is made possible by the way the Open Monitoring Distribution works – it generates a unique name for each site, which the user assigns when setting it up. This name corresponds to a Linux user and thus follows the same conventions as usernames under Linux. The necessary processes of the sites then run under the user's own Linux username.

Due to the strict separation of software and data, it is also possible to install several versions of OMD in parallel, in addition to operating several sites on one server. In doing so, OMD determines for each site which of the installed versions it will use.

This is made possible by the way OMD carries out an update. You do not have to update the complete Open Monitoring Distribution at once, rather only one site at a time. This gives you the choice of which of the sites you want to update to the new version and which not.

After installing the new OMD version via an RPM or DEB package, the desired site can be updated to the new version with the omd update command. Afterwards, the old OMD version can be uninstalled if it is no longer needed.

The copy function with the omd cp command also offers an additional, convenient way to carry out the update.

These days, there is no longer just one OMD variant, rather there are two. This is because the initiators of the project decided that it made sense to develop two specialized OMD versions. One is still the original version, which contains further extensions in addition to the original components. The second version is Checkmk, an independent and powerful monitoring solution with more than 2,000 official plug-ins for monitoring the IT infrastructure. Checkmk is fully compatible with OMD.

The decisive factor for the separate further development was the original idea of wanting to provide a perfectly-coordinated monitoring system. Checkmk founder Mathias Kettner no longer saw this as a given with a package of several optional monitoring tools, so he concentrated on the further development of Checkmk. In this way, he wanted to ensure that Checkmk would provide a finely-tuned monitoring system.

As a special OMD version, Checkmk benefits from all the advantages of the Open Monitoring Distribution. This means that by simply installing a package, you get a perfectly pre-configured Checkmk, you can run several Checkmk sites – even with differing Checkmk versions – on one server and upgrade the individual sites conveniently. The migration of a site from one Checkmk edition to another, for example from Checkmk Community to Checkmk Pro, is also possible without any problems. The control and configuration of the monitoring sites can easily be done with the omd command.

In addition, Checkmk has a built-in mechanism for creating backups and restoring Checkmk sites. The basis for this are the commands omd backup and omd restore, which pack all the data from an instance into a tar archive and unpack it again, respectively. Creating a backup file via omd backup can also be done by a site user without root permissions.

As already mentioned, after installing a DEB/RPM package, it is possible to set up Checkmk with the omd command. This overview shows the most important OMD commands for Checkmk, where MySite serves as a placeholder for the chosen name of the site (if you do not execute the command as a site user):

omd create [MySite] → Creates a new site [MySite].
omd start [MySite] → Starts all services of [MySite].
omd stop [MySite] → Stops all services of [MySite].
omd restart [MySite] → Restarts all services of [MySite].
omd rm [MySite] → Removes [MySite] and its data.
omd status [MySite] → Shows the status of [MySite].
omd config [MySite] → Opens an interactive menu that enables the configuration of [MySite].
omd update [MySite] → Updates [MySite] to a different OMD version.
omd cp [MySite] [NewSite] → Creates a copy of [MySite] with the name [NewSite].
omd backup [MySite] → Creates a backup of [MySite].
omd restore [MySite] → Restores [MySite] from a backup.
omd cleanup → Uninstalls all Checkmk versions that are not in use by any site.