1. Selecting a Checkmk edition

Before you begin installing Checkmk, you must first decide which of the four available editions you want to use:

The CRE Checkmk Raw Edition (CRE) is free, 100% open source and incorporates Nagios as its core. You can use it to comprehensively monitor complex environments. Support is available in our Forum from the Checkmk community.

The CFE Checkmk Enterprise Free Edition (CFE) is the right one for you if you want to test the Standard Edition without obligation or if you want to use Checkmk on a small scale with one site with up to 25 monitored hosts. The Free Edition contains all of the features of the Standard Edition, is free of charge and unlimited for the first 30 days. Both the Free Edition and the Raw Edition can be upgraded directly to the Standard Edition later without any extra complications.

The CSE Checkmk Enterprise Standard Edition (CEE) is primarily aimed at professional users and offers a number of interesting features beyond the scope of the Raw Edition, such as the Checkmk Micro Core (CMC) with its own very high-performance core which replaces Nagios, reporting, a sophisticated system for the visualisation of performance metrics, a flexible distribution of Checkmk monitoring agents (which obtain information from the monitored target systems), and much more. For the Standard Edition you can optionally receive professional support from us or from one of our partners.

The CME Checkmk Enterprise Managed Services Edition (CME) is a multi-client-capable extension of the Standard Edition which, via distributed monitoring, has all of the necessary functions for operating an individual Checkmk site for each one of multiple independent customers. If you want to provide these services for your customers, this is your edition. More detailed information on the concept of managed services can be found in the introduction to this article.

You can find a table of the differences between the editions on our homepage.

CEE Whenever in this User guide we discuss functions that apply to only one of the Enterprise Editions — i.e. the CEE, CFE or CME — we indicate this with the symbol as in this paragraph.

2. Selecting your version

We are continually developing all editions of Checkmk and therefore there are different versions of each edition. To get started, we generally recommend the latest stable version. A detailed overview of what other versions are available can be found in this article.

3. The software installation

The Checkmk server fundamentally requires a Linux system on which it can run. (Of course, you can still monitor Windows and other operating systems). If you do not want to set up your own Linux server, you can also run Checkmk using Docker or an appliance. There are four options in total, which we briefly present below and which are installed in different ways. When you have finished installing your variant, continue reading in the next chapter, which is about creating a site.

3.1. Linux server

The installation of Checkmk on a Linux server — whether on a 'real' or on a virtual machine — is the standard scenario. If you have basic Linux knowledge, the installation is very simple. All the software you need is either included in your Linux distribution or in our Checkmk package.

Checkmk supports the following Linux distributions: Red Hat Enterprise Linux (RHEL)/CentOS, SUSE Linux Enterprise Server (SLES), Debian and Ubuntu. For each Checkmk edition, Checkmk version and Linux distribution, there is a separate customised package from us that you can install with the package manager in your Linux distribution.

3.2. The virtual appliance

With the Checkmk virt1 virtual appliance you get a ready-to-use virtual machine with an OVA (Open Virtualization Archive) file format that you can use in a hypervisor such as VirtualBox or VMware vSphere ESXi.

In addition to Checkmk, the virtual appliance also contains the Debian Linux operating system. The advantage with the appliance, apart from a pre-installed system, is that you can configure the operating system and Checkmk completely via a graphical user interface without having to use the Linux command line. This also includes the updating of the operating system and Checkmk.

CEE The virtual appliance is available for all Enterprise Editions, and for the Free Edition as a free demo version. You can find out how to proceed with the installation in the Quick Start Guide.

3.3. The physical appliance

You can go one step further with the physical appliance — also known as the hardware appliance — in which Checkmk comes pre-installed and ready to use on a device, for example, to install directly in your data centre. You can connect two physical appliances together to form a high-availability cluster (HA cluster) in just a few steps.

The physical appliance is available for the Standard Edition and the Managed Services Edition. You can choose between several models with differing levels of maintenance. The instructions for commissioning the appliance can be found in the Quick Start Guide.

3.4. Docker container

If you would like to provide Checkmk using a Docker container, you also have this option. We support both Raw Edition and Enterprise Editions with ready-made container images that can be set up with just a few commands.

You can find the instructions for this in the article on installing as a Docker container.

4. Creating a site

Checkmk has a special feature that may seem unimportant at first, but it is one which has proven very useful in practice — you can run several independent sites of Checkmk in parallel on the same server. Each site can even run a different version of Checkmk.

Here are two common uses for this well thought-out feature: * An uncomplicated method for trying out a new Checkmk version. * The parallel operation of a test site for the monitoring of hosts that are not yet operational.

If you have just installed Checkmk on a Linux server, there will be no sites as yet. In this chapter we will show you how to create a site following an installation of Checkmk software on a Linux distribution.

Note: Checkmk appliances are administered via a web interface that also covers the creation of sites. This is explained in the article on the appliance. If you are running Checkmk in a Docker container, a site will be created for you automatically during its installation.

First choose a name for your site. This may only consist of letters and numbers. The convention here is lower case letters. In the User guide, we use the name mysite in all examples. Replace this name with your own site name.

The creation itself is very simple. As root, simply enter the command omd create followed by the name for the site:

root@linux# omd create mysite
Adding /opt/omd/sites/mysite/tmp to /etc/fstab.
Creating temporary filesystem /omd/sites/mysite/tmp...OK
Updating core configuration...
Generating configuration for core (type cmc)...Creating helper config...OK
Restarting Apache...OK
Created new site mysite with version 2.0.0.cee.

  The site can be started with omd start mysite.
  The default web UI is available at http://linux/mysite/

  The admin user for the web applications is cmkadmin with password: jEpCM9T4
  For command line administration of the site, log in with 'omd su mysite'.
  After logging in, you can change the password for cmkadmin with 'htpasswd etc/htpasswd cmkadmin'.

When creating a new site, the following events take place:

  • A Linux user (without password) and a Linux group are created with the name of the site. This user is known as the site user.

  • A home directory is created for the site in the /omd/sites directory, e.g. /omd/sites/mysite.

  • A suitable default configuration is copied into the new directory.

  • A user with the name cmkadmin and a random password is created for the web interface in ( CMK).

Note: If you receive this or a similar error message when trying to create the site:

root@linux# omd create mysite
Group 'mysite' already existing.

then a Linux user or group already exists with the site name you specified. In such a case, simply choose a different name.

Once you have created the new site, subsequent administration is no longer carried out as the root, but instead as the site user. The easiest way to become a site user is with the following command:

root@linux# su - mysite

You can see from the changed prompt that you are now logged into the site, and as the command pwd shows, you will then be automatically in the site’s home directory:

OMD[mysite]:~$ pwd

As you have seen in the output from omd create, an administrative Checkmk user named cmkadmin is automatically created when the site is created. This user is for logging into the web interface in Checkmk and has been given a random password. As the site user, you can easily change this password:

OMD[mysite]:~$ htpasswd -m etc/htpasswd cmkadmin
New password: *****
Re-type new password: *****
Updating password for user cmkadmin

By the way — whenever we give file path names in the User guide that do not begin with a slash, they refer to the home directory for the site. If you are in this directory, you can therefore use such paths directly in this way. This also applies, for example, to the file etc/htpasswd, whose absolute path here is /omd/sites/mysite/etc/htpasswd. This file contains the passwords for the Checkmk users of this site. Do not confuse this file with /etc/htpasswd.

5. Starting a site

A site can be started or stopped. The start type is automatic, which means that a started site is also restarted after a reboot of the computer. Newly-created sites nevertheless begin their lives in a stopped state. You can easily check this with the command omd status, which shows the status of all of the individual processes that are necessary to operate the site:

OMD[mysite]:~$ omd status
mkeventd:       stopped
liveproxyd:     stopped
mknotifyd:      stopped
rrdcached:      stopped
cmc:            stopped
apache:         stopped
dcd:            stopped
redis:          stopped
crontab:        stopped
Overall state:  stopped

With a simple omd start you can start the site:

OMD[mysite]:~$ omd start
Creating temporary filesystem /omd/sites/mysite/tmp...OK
Starting mkeventd...OK
Starting liveproxyd...OK
Starting mknotifyd...OK
Starting rrdcached...OK
Starting cmc...OK
Starting apache...OK
Starting dcd...OK
Starting redis...OK
Initializing Crontab...OK

As expected, afterwards the status shows all services as running:

OMD[mysite]:~$ omd status
mkeventd:       running
liveproxyd:     running
mknotifyd:      running
rrdcached:      running
cmc:            running
apache:         running
dcd:            running
redis:          running
crontab:        running
Overall state:  running

CRE Since the Raw Edition does not have all the features of the Enterprise Editions, you will see fewer services there. In addition, you will find nagios as the core instead of cmc:

OMD[mysite]:~$ omd status
mkeventd:       running
rrdcached:      running
npcd:           running
nagios:         running
apache:         running
redis:          running
crontab:        running
Overall state:  running

The omd command provides many more options for controlling and configuring sites, and these are described in the article on sites. In addition, you can find out how the directory structure for Checkmk is set up in the article on Checkmk in the command line.

6. Logging in

With the site running, you can now proceed. Each site has its own URL that you can open in your browser. This URL consists of the IP address or the host name of the Checkmk server, a slash and the name of the site, e.g. http://mycmkserver/mysite. You will find this login dialogue at this address:


Now log in with the user name cmkadmin and the password you chose or changed at the beginning. This will take you to the start page in Checkmk, which we will look at in more detail in the next chapter.

If your site has not started, you will see the following error message instead of the login dialogue:

omd site not started

If there is no site with this name at all — or you have landed on a server without Checkmk — it will look more like this:

omd site not found

Important: As soon as you are running Checkmk productively, we recommend that for security reasons you only allow access to the interface in a secured manner. You can find out what you need to do for this in the article on securing the web interface with HTTPS.

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