Problema instalacion debian

saludos

estoy tratando de instalar ruby on rails en el debian 4 etch, y tengo
problemas al tratar de instalar los gems, aca les coloco lo que me
arroja la consola a ver si alguien le ha sucedido esto antes.

gem install postgres-rp
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require': no such file to load -- zlib (LoadError) from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from /usr/local/lib/ruby/site_ruby/1.8/rubygems/package.rb:10
from
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require' from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from /usr/local/lib/ruby/site_ruby/1.8/rubygems/format.rb:9
from
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require' from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from /usr/local/lib/ruby/site_ruby/1.8/rubygems/installer.rb:11
… 11 levels…
from
/usr/local/lib/ruby/site_ruby/1.8/rubygems/command_manager.rb:103:in
process_args' from /usr/local/lib/ruby/site_ruby/1.8/rubygems/command_manager.rb:74:inrun’
from
/usr/local/lib/ruby/site_ruby/1.8/rubygems/gem_runner.rb:39:in `run’
from /usr/local/bin/gem:22

gracias por su tiempo.

Busca “no such file to load – zlib (LoadError)” en Google. Mira entre
los primeros resultados.