The Nagios web interface always offers a menu on the left frame and the current information is shown in the remaining area. You can easily access all views from the menu on the left.
In case you want to replace the standard Nagios welcome screen with your own screen, all that is needed to be done is to change the
/opt/nagios/share/main.php file. As this page is shown to everyone after they log in correctly, it can be used to provide the 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 or commonly accessed services.
It is also possible to extend the menu on the left, which is defined in the
/opt/nagios/share/side.php file. This way, quick links can be added to the menu and/or unused functionality can be removed from it.
Throughout the rest of this chapter, we will use the configuration that is different from the one we created in the previous chapter. This will allow to show more functionality in Nagios and its web interface. In the configuration used in this chapter, we have four hosts (two Linux-based, one Windows-based, and one network access point running OpenWrt software) with a total of 18 services being checked on those hosts, where two of these services are failing.
Checking the tactical overview
Nagios offers a panel that shows an overall status of all hosts, services, and other features. It can be accessed by clicking on the Tactical Overview link from the menu on the left. You can easily assess the scale of problems, such as 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 an example screenshot of the Tactical Overview page. All 4 hosts are up and running, 16 services are in the OK state, and 2 are Critical:
Tactical Overview presents the overall information on Nagios and monitoring. The page informs about the host and service conditions. It shows how many hosts and services are in which status. It also shows if any hosts and services have their checks, notifications, or event handlers disabled.
Performance information is shown in the top right-hand corner. It shows details on checks that have been performed. It also reports latency when performing checks and the time that it takes to perform checks, on average. These values are pretty important since if there are too many checks scheduled, then 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.
Below the performance information there is a status showing host and service health. It contains bars showing the number of hosts and services that are in an OK state. If all services are currently working properly then the bar spans to full width and is green. If some hosts or services are not working then the color of the bar will change to yellow or red accordingly.
Tactical Overview can also be used to view hosts or services list filtered to specific criteria. Clicking on any status count text in the Network Outages, Hosts, or Services section will show a list of hosts or services with specified status; if we would click on the 16 Ok text in the Services section, it will show a list of all services with the OK status.
Viewing the status map
Nagios can show a graphical map of host parent-child relations along with the statuses. It can be accessed by clicking on the Map link in the menu on the left of the Nagios web interface. This can be used to keep track of hosts along with their statuses. So, you can see how a host being down causes other parts of your network to be unreachable.
The following is an example screenshot of a status page depicting our Nagios Process monitoring all four hosts:
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.