Many Debian (and Ubuntu, which is compatible) sysadmins and users prefer to use the APT (as in apt-get) package management system for handling the installation of everything on their system. With its separate RubyGems packaging system, however, Ruby can cause a dilemma. Read more here

While some Ruby stuff is available through the regular repositories, it can be out of date and unreliable. No longer.. DebGem provides an APT repository with Debian and Ubuntu packages for “virtually all gems” available on RubyForge and Github.