How Do I Get My Hands on It?
Fully functional demo versions of XI (60-day expiration) are available from nagios.org. You may download self-contained installers, or VMware disk images with XI preinstalled. The latter can be run by any system that supports the free vmplayer utility, while the former requires a relatively recent Red Hat or CentOS install.
The reason for the RHEL dependency is the dizzying array of packages that must exist for XI to run. The XI developers have chosen to rely heavily on YUM to satisfy the requisite dependencies, so although it’s possible to run XI on other distros, you won’t be able to use the official installation script to get it up and running on anything other than a Red Hat or CentOS system.