Installation of OpenNMS How-To
While it's mostly out of date, some of the concepts described in the older OpenNMS Install Guide might be useful to you, too. However, it is recommended that you start with the quick start instructions linked here.
Debian packages are available for use with the newest stable Debian release (as well as most modern Ubuntu releases). To do so, follow the Debian installation instructions.
OpenNMS can be installed on Windows using the java-based installer, documented in the Windows installation instructions.
To build from source, follow the Building OpenNMS HOWTO.
Folks have documented a number of install logs and howtos for installing on specific platforms. It is recommended to try the Yum/Debian/Windows installation instructions above if possible, but for other platforms, or specific needs, these may prove useful: