I had 800MB of space taken up by old kernels, header files, and kernel modules. On most modern systems, this is no big deal. On my netbook, with it’s 30GB ssd, every gig is precious.
Ruby Version Manager (rvm) is a shell function that lets you easily switch between versions of ruby (and their corresponding gems). These instructions walk you through installing rvm, ruby, and rails on linux for a single-user setup (files kept in ~/.rvm). Following these instructions as root should set everything up for a multi-user installation.
