unfortunately, ubuntu 8.04 hardy comes with ruby version 1.8.6 by default. The latest rubygems doesn’t work well with this version. so we need to get a new version for ruby.
might want to check if you have these libraries first:
sudo apt-get install libncurses5-dev
sudo apt-get install libreadline5-dev
Download the ruby the latest source and compile it.
wget ftp://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.1-p243.tar.gz
tar -xzvf ruby.19.1-p243.tar.gz
cd ruby1.9.1-p243
./configure
make
make install
if getting errors like so:
cd ruby.19.1-p243/ext/readline
ruby extconf.rb
make
sudo make install
If you have an old gem running, you can update it by
gem update --system
else you might want to visit rubygems.org to get the latest file... then extract and compile it just like before.