packages.rb

# role

name 'base-packages'
default_attributes :packages => {
  'build-essential' => "latest",
  'gcc' => "3.0"
}
run_list "recipe[install-packages]"

# cookbooks/install-packages/recipe/default.rb

node.packages.each do |name, version_number|
  package name do
    version vesion_number if version_number != "latest" 
    action :install
  end 
end