Ttgjyuk

I tried installing rails according to this guide, and when I do, I get this error:

$ sudo gem install rails
 WARNING: Error fetching data: Errno::ENOENT: No such file or directory - getaddrinfo (http://rubygems.org/specs.4.8.gz)
 WARNING: Error fetching data: Errno::ENOENT: No such file or directory - getaddrinfo (http://rubygems.org/latest_specs.4.8.gz)
 Building native extensions. This could take a while...
 ERROR: Error installing rails:
 ERROR: Failed to build gem native extension.

 /usr/bin/ruby1.9.1 extconf.rb
 /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)
 from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
 from extconf.rb:1:in `<main>'


 Gem files will remain installed in /var/lib/gems/1.9.1/gems/json-1.8.0 for inspection.
 Results logged to /var/lib/gems/1.9.1/gems/json- 1.8.0/ext/json/ext/generator/gem_make.out

I've never seen anything like this before, so any feedback would be greatly appreciated.

Try to re-install Ruby, then Gem and then install Rails. Problem maybe is on Ruby or Gem.

Try using rvm or rbenv; they both works great... I personally prefer rvm because I want to keep gem-sets separate for different projects. See rbenv repository if you want to simple installation just using one ruby version. I've written a blog post on Rbenv Installation

1. 
   

   Installing rbenv

   
   
   

   Setup:

   
   
   

   sudo apt-get update
   sudo apt-get upgrade -y
   

   
   
   

   Install required components for Ruby and other dependencies.

   
   
   

   sudo apt-get install git-core -y
   sudo apt-get install curl -y
   sudo apt-get install build-essential openssl libreadline6 libreadline6-dev curl git-core zlib1g zlib1g-dev libssl-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt-dev autoconf libc6-dev libgdbm-dev ncurses-dev automake libtool bison subversion pkg-config libffi-dev
   git clone git://github.com/sstephenson/rbenv.git ~/.rbenv
   echo ‘export PATH="$HOME/.rbenv/bin:$PATH"’ >> ~/.profile
   echo ‘eval "$(rbenv init -)"’ >> ~/.profile
   

   
   
   

   (Note: modify .bash_profile , .bash_login or .zshrc according to your needs.)

   
   
   

   Now install some required rbenv plugins.

   
   
   

   cd ~/.rbenv/
   mkdir plugins
   cd ~/.rbenv/plugins
   git clone git://github.com/sstephenson/ruby-build.git
   

   
   
   

   Restart the terminal.

   
   


2. 
   

   Installing Ruby

   
   
   

   rbenv install 1.9.3-p385
   

   
   
   

   Set your global Ruby version.

   
   
   

   rbenv global 1.9.3-p385
   rbenv rehash
   ruby -v
   

   
   


3. 
   

   Install Ruby on Rails Framework

   
   
   

   gem install bundler
   gem install rails
   

   
   
   

   (Don't panic, installing rails will take some time.)