Using the Web Interface
Nagios Web interface always offers a menu in the left frame, while current information is shown in the remaining area. You can easily access all views from the left-side menu.
In case you want to replace the standard Nagios welcome screen with your own, all you need to do is change the /opt/nagios/share/main.html file. As this page is shown to everyone after they log in correctly, it can be used to provide administrators with some guidelines on how Nagios monitoring is used within your company, and what should be done in certain circumstances. It can also be used to define links to commonly-checked hosts and commonly-accessed services.
It is also possible to extend the left side menu, which is defined in the /opt/nagios/share/side.html file. This way, quick links can be added to the menu and/or unused functionality can be removed from it.
Henceforth in this chapter, we will use configuration that is far more complex than the one we created in the previous chapter. This will allow us to see more functionality in Nagios and its web interface.
Tactical Overview
Nagios offers a panel that shows the overall status of all of the hosts, services and other features. It can be accessed by clicking on the Tactical Overview link in the left-side menu. You can use this page to assess number of hosts and services failing, flapping and pending checks. It also shows how many hosts are unreachable due to other hosts being down.
The following is a screenshot of the Tactical Overview page:
The tactical Overview presents overall information on Nagios and its monitoring. The page provides information about host and service conditions. It shows how many hosts and services are in which status. It also shows if any hosts or services have their checks, notifications, or event handlers disabled.
Performance information is shown in the top right-hand corner. This shows details of the checks that have been performed. It also reports latency while performing the checks and the average time that it takes to perform these checks. These values are quite important because if there are too many checks scheduled, Nagios might not be able to perform some of them. Usually, you should tweak your Nagios installation in cases where latency is getting larger than a couple of seconds.
Following this information is a status showing host and service health. This contains bars showing the number of hosts and services that are in an OK state. If all of the services are currently working properly, the bar is green across its full width. If some hosts or services are not working, the color of the bar will change to yellow or red, accordingly.
The Tactical overview can also be used to view hosts or services list filtered on specific criteria. Clicking on any status count text in Network Outages, Hosts or the Services section will show a list of hosts or services with the selected status. If we click on the text 19 Ok in the Services section, it will show a list of all of the services with a status of OK.
Similarly, if any object is flagged as red in the Monitoring Features section, it is possible to go to a list of hosts or services with the selected symptoms. For example, if we click on 3 Services Disabled in the Notifications section, a list of these three services will be displayed.
Status map
Nagios allows the display of a graphical map of host parent-child relations, along with their statuses. This can be accessed by clicking on the Status Map link on the left-side menu. This information can be used to keep track of hosts and their statuses. In this way, you can see how a host being down causes other parts of your network to be unreachable.
The following is a screenshot of a status page:
The status page can be shown in many ways. The preceding image shows a circular tree of all hosts. It is also possible to show a top-down tree of all hosts.
Further, it is possible to show all your machines in a 3D environment using Virtual Reality Modeling Language (VRML). This can be accessed by clicking on the 3-D Status Map link on the left-side menu.