Installation with OMD

Today, the fastest way to get a working Nagios and Check_MK installation is using OMD. There is a free community version and a subscriber version with various additional features available. The difference between the versions is explained in detail here.

In this article we show you how to carry out the installation and to configure the first host and services.

1. Linux Installation

At first you need to install a basic linux system with a distribution of your choice. Supported Distributions are Debian, Ubuntu, CentOS, RedHat and SLES11. Before you choose a particular version, service pack and architecture you should check if a corresponding download package of OMD is available for that version. For most newer distributions this should be that case.

You can find an overview of available packages here:

• For the free community version: Download page of the OMD community project
• For your subscription: Download page of the Check_MK Monitoring Project

Please note that OMD is installed to the /opt/omd directory, which on some linux installations might be on the root filesystem with limited disk space available. /opt/omd will contain your OMD software as well as your sites, potentially including a lot of data. So if you plan to build a large OMD site you might want to either mount a dedicated partition on /opt, or link it to some other directory on another partition with at least several GB disk space available. Note that very large sites with several 1000 hosts may require several 100GB of disk space when they also collect performance data.

Upon installation a link from /omd to /opt/omd is also created for your convenience.

2. Installing the OMD Package

Once you have your linux server up and running you can download the corresponding package and install it.

2.1. Debian and Ubuntu

The easiest way is to use gdebi to install the package, since it automatically installs all packages the omd package depends on.

root@linux# gdebi omd-2013.08.27.mk_0.wheezy_amd64.deb

Since OMD requires two apache proxy modules, you will need to enable these afterwards:

root@linux# a2enmod proxy_http
root@linux# /etc/init.d/apache2 restart

2.2. SLES 11

On SLES zypper is a convenient tool to install OMD and all the depending packages. If you need to install from DVDs, you must have the first SLES 11 DVD and also the first SLE 11 SDK DVD available. Also be careful to select the matching service pack of the DVDs and the OMD-package.

root@linux# zypper install omd-1.2.2p2.mk-sles11sp1-30.i586.rpm

2.3. RedHat and CentOS

On RedHat and CentOS you first need to install the epel repository. For CentOS 5 this can be done with the following command:

root@linux# rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-4.noarch.rpm

To install the OMD package yum is the way to go.

root@linux# yum install --nogpgcheck omd-0.42-0.42-centos55.14.x86_64.rpm

The option --nogpgcheck might be needed if the package is not signed.

3. Creating your first OMD site

OMD Sites are completely independent instances of OMD. You can have several sites on your OMD host, for example one for production use, one for configuration tests, and one for upgrade tests.

Creating your first OMD site is very easy. You just have to choose a site name, say prod. Then, as root user, you simply type

root@linux# omd create prod
Adding /opt/omd/sites/prod/tmp to /etc/fstab.
Restarting Apache...OK
Creating temporary filesystem /omd/sites/prod/tmp...OK
Created new site prod with version 2013.08.01.mmk.

  The site can be started with omd start prod.
  The default web UI is available at http://<yourhost>/prod/
  The admin user for the web applications is omdadmin with password omd.
  Please do a su - prod for administration of this site.

A site user and group prod is created, as well as a home directory for the user in /omd/sites/prod. You should now switch to that user and start the site (even though sites can be started and maintained as the root user as well).

root@linux# su - prod
user@host:~$ omd start
Starting dedicated Apache for site prod...OK
Starting Livestatus Proxy-Daemon...OK
Starting rrdcached...OK
Starting npcd...OK
Starting nagios...OK
Initializing Crontab...OK

Now you can already visit the Check_MK GUI of your site with your browser:

http://mysite/prod/

We will soon configure the first host and checks, but first we take a closer look at the omd command and how to manage your site with it.

4. The omd-command

The omd command is used to create, start, stop and update sites, and to do many more things. omd can be executed as site user to modify just that site, or as root user. As the root user omd offers more option such as copying, renaming, disabling or uninstalling sites.

user@host:~$ omd
Usage (called as site user):

 omd help                        Show general help
 omd version    [SITE]           Show version of OMD
 omd versions                    List installed OMD versions
 omd sites                       Show list of sites
 omd update                      Update site to other version of OMD
 omd start      [SERVICE]        Start services of one or all sites
 omd stop       [SERVICE]        Stop services of site(s)
 omd restart    [SERVICE]        Restart services of site(s)
 omd reload     [SERVICE]        Reload services of site(s)
 omd status     [SERVICE]        Show status of services of site(s)
 omd config     ...              Show and set site configuration parameters
 omd diff       ([RELBASE])      Shows differences compared to the original version files
 omd umount                      Umount ramdisk volumes of site(s)

root@linux# omd
Usage (called as root):

 omd help                        Show general help
 omd setup                       Prepare operating system for OMD (installs packages)
 omd uninstall                   Remove OMD and all sites!
 omd setversion VERSION          Sets the default version of OMD which will be used by new sites
 omd version    [SITE]           Show version of OMD
 omd versions                    List installed OMD versions
 omd sites                       Show list of sites
 omd create     SITE             Create a new site (-u UID, -g GID)
 omd init       SITE             Populate site directory with default files and enable the site
 omd rm         SITE             Remove a site (and its data)
 omd disable    SITE             Disable a site (stop it, unmount tmpfs, remove Apache hook)
 omd enable     SITE             Enable a site (reenable a formerly disabled site)
 omd mv         SITE NEWNAME     Rename a site
 omd cp         SITE NEWNAME     Make a copy of a site
 omd update     SITE             Update site to other version of OMD
 omd start      [SITE] [SERVICE] Start services of one or all sites
 omd stop       [SITE] [SERVICE] Stop services of site(s)
 omd restart    [SITE] [SERVICE] Restart services of site(s)
 omd reload     [SITE] [SERVICE] Reload services of site(s)
 omd status     [SITE] [SERVICE] Show status of services of site(s)
 omd config     SITE ...         Show and set site configuration parameters
 omd diff       SITE ([RELBASE]) Shows differences compared to the original version files
 omd su         SITE             Run a shell as a site-user
 omd umount     [SITE]           Umount ramdisk volumes of site(s)

General Options:
 -V <version>                    set specific version, useful in combination with update/create
 omd COMMAND -h, --help          show available options of COMMAND

5. Configuring your site

To configure your site as a site user, you type:

user@host:~$ omd config

You get a simple graphical interface to the configuration options of your site.

For the your first installation you dont need to change any of the options, since most of them are for expert users only. However, here is a short overview of what you can do using this interface:

5.1. Basic

• Autostart: Lets you choose if your site is started automatically during reboot of your server
• Core: Allows you to use the traditional nagios core or the microcore (subscription users only)
• Crontab: Disables or enables site specific crontabs at boot time
• tmpfs: Disables or enables the use of a ramdisk for temporary files

5.2. Web GUI

• Apache Mode: Lets you choose to run a dedicated apache webserver for this site, or use the system webserver process directly
• Apache TCP_ADDR: Lets you choose the ip address of your apache webserver
• Apache TCP_PORT: Lets you choose the tcp port apache uses
• Default_GUI: Lets you choose other GUIs besides Check_MKs multisite GUI
• DOKUWIKI_AUTH: Enables the use of the dokuwiki user database for authentication instead of ~/etc/passwd

• MULTISITE_AUTHORISATION: Lets multisite manage the permissions of the addon users
• MULTISITE_COOKIE_AUTH: Enable or disable cookie based authentication
• NAGIOS_THEME: Switch between installed Nagios themes

5.3. Addons

• MKEVENTD: This option enables mkeventd - the event correlation and classification daemon of Check_MK
• MKNOTIFYD: Enables of disables Check_MKs notification spooler
• NAGVIS_URLS: Lets you choose which GUI is used when clicking on the NagVis map icons
• PNP4NAGIOS: Lets you enable or disable PNP4Nagios, a great addon to store nagios performance data to round robin databases

5.4. Distributed Monitoring

• LIVEPROXYD: This option enables the livestatus proxy daemon
• LIVESTATUS_TCP: Make the livestatus proxy daemon listen on a tcp port in addition to the unix socket

6. Configuring the first host and checks

The best choice for a first host to be monitored with Check_MK is the monitoring server itself.

6.1. Installing the Check_MK Agent on your monitoring server

In order to do that you need to install the Check_MK Agent on the server, which is very easy. After verifying that you have installed xinetd, you can find agents for you linux distribution on the Check_MK Download Page, and simply install them with your package manager.

For a more detailed description of the installation process, see the article about Installing the Linux Agent.

6.2. Configuring your Host

To configure your first host, choose "Create New Host" in "Hosts & Folders" of the WATO Configuration Menu:

and enter the following information as marked (choose your own name for your monitoring server), and click on the Save & Go to Services button.

6.3. Configuring services on your host

At this point, I am sure you will notice the advantage of using Check_MK. Instead of configuring services for your hosts, by clicking the Save & Go to Services Button, Check_MK has automatically done an inventory of the services on your server already. As a result you see a list of the services found.

If you click on the Save Manual Check Configuration button, the services will be saved. After clicking Activate Changes at the left top of the page, a nagios configuration will be created, and Check_MK will regularly send the results to nagios.

From then, you can see the check results in the multisite GUI. That was easy, right ?