gistfile1.rb

### Rakefile

task :template do
  require 'yaml'
  require 'erb'

  base    = File.join(File.dirname(__FILE__), 'config')
  source  = File.join(base, 'dna.json.erb')
  target  = File.join(base, 'dna.json')
  recipes = ENV['recipe'] || %w(packages users gems)
  @to_run = recipes.collect {|r| %Q("#{r}")}.join(',')

  t = ERB.new(File.read(source)).result(binding)
  File.open(target, 'w') {|f| f.write(t)}
end

desc "Run chef-solo cookbook(s)."
task :solo => :template do
  sh("chef-solo -l debug -c config/solo.rb -j config/dna.json")
end

### dna.json

{
  "user":"root",
  "packages":[],
  "gems":[],
  "users":[],
  "recipes":[<%= @to_run %>]
}