Great how-to is located at http://www.rubywizards.com/viewtopic.php?pid=19 Here’s the copy of it:
* Bring up the terminal, login as system root, and create temporary directory to store downloaded files.
[~/] mkdir local
[~/] cd local
* Download official source distribution. This will create a file named ruby-1.8.5.tar.gz in your local directory.
[~/local] wget ftp://ftp.ruby-lang.org/pub/ruby/ruby-1.8.5.tar.gz
* Extract all the files from downloaded archive. This will create local/ruby-1.8.5 subdirectory that stores extracted files.
[~/local] tar xvfz ruby-1.8.5.tar.gz
* Install GNU C++ compiler you’ll need to build Ruby from source.
[~/local] apt-get install build-essential
* Run configure utility to determine your system configuration.
[~/local] cd ruby-1.8.5
* Run make command to compile and build Ruby.
* Test newly built Ruby executable by running regression test suite. Upon successfull completion you’ll see a message like: “Finished in 44.904424 seconds. 1440 tests, 13585 assertions, 0 failures, 0 errors.”
[~/local/ruby-1.8.5] make test-all
* Install Ruby onto your system. This will move Ruby executable and utilities to /usr/local/bin and standard Ruby libraries to /usr/local/lib/ruby.
[~/local/ruby-1.8.5] make install
* Install Ruby documentation. This will compile Ruby documentation in format required for ri command.
[~/local/ruby-1.8.5] make install-doc
At this point the installation of Ruby 1.8.5 is complete. If you had previous version of Ruby installed in /usr/local/bin, you should take two extra steps:
* Make sure /usr/local/bin comes before /usr/bin in your $PATH:
[~/local/ruby-1.8.5] echo $PATH
* Logout from your current terminal session and login again to reload hashed value of ruby:
[~/local/ruby-1.8.5] which ruby
[~/local/ruby-1.8.5] ruby -v
ruby 1.8.5 (2006-08-25) [i686-linux]
Mike Dvorkin, Ruby Wizards Admin