How to monitor Linux servers with help of Checkmk

How to monitor Linux servers with help of Checkmk

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How to monitor Linux servers with help of Checkmk – Guide

As a system / network administrator, it is your responsibility to maintain control over the Linux servers in your data center (whether on-premises or in the cloud). Given that the Linux platform has a significant number of tools to help you monitor these servers, you may not know where to start. Among these many titles, there is a specific software package that you should definitely try out. That monitor is Checkmk.

Checkmk can monitor your servers, desktops, applications, networks and cloud environments, all from a well-designed web-based GUI dashboard.

I’ll walk you through the process of installing Checkmk and then adding a monitoring agent. We’ll do both on Ubuntu Server 20.04, but be aware that this software supports Debian and RHEL based distributions.

Start monitoring with Checkmk

It’s time to switch to the Checkmk user interface in your web browser. Each Checkmk website has its own URL, made up of the IP address or hostname of its monitoring server and the name of the Checkmk website. In this example, my Checkmk installation is located at monitoring-host-server / checkmk_demo /.

  • Open the link to your Checkmk website in your browser. You can open the link shown on your terminal.
  • Log in as the cmkadmin user, using the password you copied from the terminal.
  • Once you are logged in, you will see an empty dashboard.
  • Click the User category in the left sidebar, then click Change Password under Profile. Here you can change your password.
  • Monitoring configuration

    Checkmk supports several ways to monitor servers and the best method for server monitoring is usually using Checkmk agents. Before adding a server, you need to install the agent.

  • In the left sidebar, click on Configuration (the button with a sprocket).
  • This is the control panel where you perform all the configurations and find the monitoring agents. There are some user interface differences between Raw Edition and Enterprise Edition, but all screenshots in this article are open source Raw Edition.

  • Click Agents and select the appropriate package for your operating system.
  • The bundled agents for Linux are provided in RPM and DEB file formats.
  • Select an agent
  • Download and install the agent on your monitoring host.
  • You can test whether the agent works correctly by running the check_mk_agent command on your server endpoint.

    Adding a host

    Once the agent is installed, go back to the Setup screen and select Hosts.

  • Click Add Host.
  • Add your server name in Hostname.
  • If you have DNS set up on your network, Checkmk resolves the IP address to its hostname automatically. Otherwise, add the IP address by clicking the checkbox next to IPv4 Address. If you add an IP address, you can choose any hostname you prefer. Leave the other areas unchanged.

    Click Save and go to service configuration. Checkmk now automatically discovers all relevant monitoring services on that host and lists them as Undecided services. Also, as you can see in the screenshot, Checkmk automatically adds labels depending on the device type.

    Click Fix All to monitor all of this. This adds all detected services and host labels to your monitoring dashboard and removes missing services. Of course, you can manage the services manually, but the Fix All function makes this much easier.

    Host monitoring fix

    Then activate your changes by clicking on the field highlighted with the yellow exclamation point (!) in the upper right corner. Click Activate on selected sites and you have successfully added the first server to your monitor.

    Requiring explicit activation for changes is a security mechanism. All changes made are listed first under Pending Changes so that you can review any changes before they affect your monitoring. Checkmk differentiates between Setup as a configuration environment, in which you manage hosts, services and settings, and the area called Monitor, in which actual operational monitoring takes place. New hosts and other configuration changes initially do not affect monitoring. You must activate them before they go into production.

    SNMP monitoring

    In addition to server monitoring, another essential monitoring task is network monitoring. As an example, I would like to show you how to monitor a switch over SNMP. All you have to do is make sure the SNMP agent on the device you want to monitor is enabled and the Checkmk server can access this device.

  • Go to Setup > Hosts and click Add host.
  • Enter the hostname and IP address (as required).
  • By default, Checkmk assumes you use a Checkmk agent, so you need to edit it under Monitoring Agents.

    Activate the checkbox next to SNMP and change the checkbox to your SNMP version (most likely ‘SNMP v2 or v3’).

    Checkmk also assumes by default that its SNMP community is public because it is also the default on most SNMP devices. If that’s the case, you can leave the SNMP credentials box unchecked (like I did). Otherwise, you must check this box and add your SNMP credentials here.

    As before, click Save and go to Service Configuration and Checkmk will discover all currently online interfaces, uptime and SNMP verification information.

    If a monitoring plugin exists for a particular device type, Checkmk automatically detects more monitoring services.

  • Click Fix All and accept the changes.
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