In this recipe, you'll learn a shortcut to building groups of hosts using regular expressions tested against their hostnames.
This recipe is likely only of use to you if you use a naming convention for your hosts that allows them to be reasonably grouped by location, function, or some other useful metric by a shared string in their hostnames.
You will need to have a server running Nagios Core 4.0 or later, have access to the command line to change its configuration, and understand the basics of how host and servicegroups work. These are covered in the Creating a new hostgroup and Creating a new servicegroup recipes in Chapter 1, Understanding Hosts, Services, and Contacts.
In this example, we'll group three existing hosts named
web-server-03 into a new hostgroup,
web-servers, based only on their hostnames.