Configuring Check_MK

1. Introduction

Check_MK distinguishes between the actual monitoring where you view host/service statuses, and the configuration environment in which you maintain hosts/services and settings.

Changes in the configuration - e.g. adding a new host - will initially have no effect on the monitoring. Changes must first be activated (by {{Activate Changes}}) in order to take effect. This might seem a little cumbersome, but it does have the advantage that more complex changes can be prepared without haste before being put into production. For example, after adding a new host you might want to define thresholds or remove some services before 'arming' the new component.

The tool for configuring Check_MK via GUI is called the WATO (Web Administration Tool). WATO maintains all configurations in a conventional text data format which experienced users can edit manually or even create with scripts. WATO can be accessed via the corresponding element in the sidebar. This element is included as standard and offers direct access to all WATO modules.

Whenever you make a change to the monitoring configuration using WATO, this change will at first be picked up and held as pending. Such changes can be identified by the button in the WATO modules and respectively the button in the sidebar. Both of these buttons open a list of the changes:

With the Activate Changes button the configuration data from WATO will be used to generate a new configuration for the monitoring core, and instruct the core to immediately begin using the new configuration:

The list of pending changes is subsequently cleared. These entries are not lost however, they can be called up with the Audit Log button. Here you can find a log file of all changes that have been made using WATO.

2. Snapshots

Whenever you activate changes in version 1.2.8 or earlier, WATO automatically creates a backup of the configuration. The list of these backups is accessed via the WATO module {{Backup & Restore}}:

A click on (details of a snaphot), and then a click on Restore Snapshot copies this back into the configuration. Important note: Only the configuration will be restored - the monitoring's state and history will not be affected.

This feature is not available anymore since version 1.4.0. It is currently in a rework progress.

3. Important WATO modules

WATO includes numerous modules - one for each important aspect of Check_MK. The following modules are particularly important:

Main Menu A list of all WATO modules, each with a short description
Monitoring Agents Here you will find Check_MK agents for Linux, Windows and other operating systems. In the  Check_MK Enterprise Edition you can also configure, package and automatically update the agents via WATO.
Hosts Management of the hosts to be monitored - perhaps the most important module.
Global Settings Global settings - those that do not apply to specific hosts, services or users.
Host & Service Parameters All settings for specific hosts or services are found here. The configuration procedure is rule based.

4. Quick access

Once you have worked longer with WATO you will know the icons off by heart. Then the smaller version of the WATO menu for the sidebar can be recommended: