Puppet, an automated administrative engine for your Linux and Unix systems, performs administrative tasks (such as adding users, installing packages, and updating server configurations) based on a centralized specification.
Documentation (and detailed install instructions) can be found online at the Puppet Wiki.
Generally, you need the following things installed:
Ruby >= 1.8.1 (earlier releases might work but probably not)
The Ruby OpenSSL library. For some reason, this often isn't included in the main ruby distributions. You can test for it by running 'ruby -ropenssl -e "puts :yep"'. If that errors out, you're missing the library.
If your distribution doesn't come with the necessary library (e.g., on Debian and Ubuntu you need to install libopenssl-ruby), then you'll probably have to compile Ruby yourself, since it's part of the standard library and not available separately. You could probably just compile and install that one library, though.
The Ruby XMLRPC client and server libraries. For some reason, this often isn't included in the main ruby distributions. You can test for it by running 'ruby -rxmlrpc/client -e "puts :yep"'. If that errors out, you're missing the library.
Facter => 1.1.1 You can get this from your package management system or the Facter site