NIPAP is officially supported on Debian and Debian derivatives. This includes pre-built packages, an automated installation (using Debians post-installation script) and above all, that it is tested.
If you are running a Debian system or a Debian derivative, see installing on Debian for instructions.
NIPAP should be able to run on any Unix-like operating system but you will need to install dependencies and NIPAP manually. See installing on Unix systems for instructions.
For upgrading on Debian / Ubuntu make sure you use:
The 'upgrade' command will not install any new dependencies and since it's fairly common that we introduce new dependencies in NIPAP it's prudent to always use dist-upgrade.