Rails 2.2 - undefined method 'write_inheritable_attribute'

After installing Rails 2.2, I got what appears to be a common problem, where write_inheritable_attribute is no longer found.

$ rails test
/usr/lib/ruby/gems/1.8/gems/rails-2.2.2/bin/../lib/rails_generator/options.rb:32:in `default_options': undefined method `write_inheritable_attribute' for Rails::Generator::Base:Class (NoMethodError)
       from /usr/lib/ruby/gems/1.8/gems/rails-2.2.2/bin/../lib/rails_generator/base.rb:90
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
       from /usr/lib/ruby/gems/1.8/gems/rails-2.2.2/bin/../lib/rails_generator.rb:34
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
       from /usr/lib/ruby/gems/1.8/gems/rails-2.2.2/bin/rails:13
       from /usr/bin/rails:19:in `load'
       from /usr/bin/rails:19

But this is clearly defined in activesupport-2.2.2. If you encounter this problem, check to see if you can load activesupport in irb:

$ irb
irb(main):001:0> require 'rubygems'
=> true
irb(main):002:0> require 'activesupport'
LoadError: no such file to load -- iconv
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
       from /usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/inflector.rb:3
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
       from /usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support.rb:26
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
       from /usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/activesupport.rb:1
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
       from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
       from (irb):2

If you see "LoadError: no such file to load -- iconv" your problem is a missing libiconv, which supports internationalization in Rails 2.2.

The rails wiki has the instructions on how to install and build iconv if you need them.

Hope this helps....

Update: For Debian, I got the same error, but had a different solution.