About the Recipe DSL

The Recipe DSL is a Ruby DSL that is primarily used to declare resources from within a recipe. The Recipe DSL also helps ensure that recipes interact with nodes (and node properties) in the desired manner. Most of the methods in the Recipe DSL are used to find a specific parameter and then tell the chef-client what action(s) to take, based on whether that parameter is present on a node.

Because the Recipe DSL is a Ruby DSL, then anything that can be done using Ruby can also be done in a recipe, including if and case statements, using the include? Ruby method, including recipes in recipes, and checking for dependencies.

Use Ruby

Common Ruby techniques can be used with the Recipe DSL methods.

if Statements

An if statement can be used to specify part of a recipe to be used when certain conditions are met. else and elseif statements can be used to handle situations where either the initial condition is not met or when there are other possible conditions that can be met. Since this behavior is 100% Ruby, do this in a recipe the same way here as anywhere else.

For example, using an if statement with the platform node attribute:

if node['platform'] == 'ubuntu'
  # do ubuntu things
end

case Statements

A case statement can be used to handle a situation where there are a lot of conditions. Use the when statement for each condition, as many as are required.

For example, using a case statement with the platform node attribute:

case node['platform']
when 'debian', 'ubuntu'
  # do debian/ubuntu things
when 'redhat', 'centos', 'fedora'
  # do redhat/centos/fedora things
end

For example, using a case statement with the platform_family node attribute:

case node['platform_family']
when 'debian'
  # do things on debian-ish platforms (debian, ubuntu, linuxmint)
when 'rhel'
  # do things on RHEL platforms (redhat, centos, scientific, etc)
end

include? Method

The include? method can be used to ensure that a specific parameter is included before an action is taken. For example, using the include? method to find a specific parameter:

if ['debian', 'ubuntu'].include?(node['platform'])
  # do debian/ubuntu things
end

or:

if %w{rhel}.include?(node['platform_family'])
  # do RHEL things
end

Array Syntax Shortcut

The %w syntax is a Ruby shortcut for creating an array without requiring quotes and commas around the elements.

For example:

if %w{debian ubuntu}.include?(node['platform'])
  # do debian/ubuntu things with the Ruby array %w{} shortcut
end

Include Recipes

A recipe can include one (or more) recipes located in external cookbooks by using the include_recipe method. When a recipe is included, the resources found in that recipe will be inserted (in the same exact order) at the point where the include_recipe keyword is located.

The syntax for including a recipe is like this:

include_recipe 'recipe'

For example:

include_recipe 'apache2::mod_ssl'

If the include_recipe method is used more than once to include a recipe, only the first inclusion is processed and any subsequent inclusions are ignored.

Reload Attributes

Attributes sometimes depend on actions taken from within recipes, so it may be necessary to reload a given attribute from within a recipe. For example:

ruby_block 'some_code' do
  block do
    node.from_file(run_context.resolve_attribute('COOKBOOK_NAME', 'ATTR_FILE'))
  end
  action :nothing
end

Accessor Methods

Attribute accessor methods are automatically created and the method invocation can be used interchangeably with the keys. For example:

default.apache.dir          = '/etc/apache2'
default.apache.listen_ports = [ '80','443' ]

This is a matter of style and preference for how attributes are reloaded from recipes, and may be seen when retrieving the value of an attribute.

Recipe DSL Methods

The Recipe DSL provides support for using attributes, data bags (and encrypted data), and search results in a recipe, as well as four helper methods that can be used to check for a node’s platform from the recipe to ensure that specific actions are taken for specific platforms. The helper methods are:

• platform?
• platform_family?
• value_for_platform
• value_for_platform_family

attribute?

Use the attribute? method to ensure that certain actions only execute in the presence of a particular node attribute. The attribute? method will return true if one of the listed node attributes matches a node attribute that is detected by Ohai during every chef-client run.

The syntax for the attribute? method is as follows:

attribute?('name_of_attribute')

For example:

if node.attribute?('ipaddress')
  # the node has an ipaddress
end

cookbook_name

Use the cookbook_name method to return the name of a cookbook.

The syntax for the cookbook_name method is as follows:

cookbook_name

This method is often used as part of a log entry. For example:

Chef::Log.info('I am a message from the #{recipe_name} recipe in the #{cookbook_name} cookbook.')

data_bag

A data bag is a global variable that is stored as JSON data and is accessible from a Chef server. A data bag is indexed for searching and can be loaded by a recipe or accessed during a search.

Use the data_bag method to get a list of the contents of a data bag.

The syntax for the data_bag method is as follows:

data_bag(bag_name)

Examples

The following example shows how the data_bag method can be used in a recipe.

Get a data bag, and then iterate through each data bag item

data_bag('users') #=> ['sandy', 'jill']

Iterate over the contents of the data bag to get the associated data_bag_item:

data_bag('users').each do |user|
  data_bag_item('users', user)
end

The id for each data bag item will be returned as a string.

data_bag_item

A data bag is a global variable that is stored as JSON data and is accessible from a Chef server. A data bag is indexed for searching and can be loaded by a recipe or accessed during a search.

The data_bag_item method can be used in a recipe to get the contents of a data bag item.

The syntax for the data_bag_item method is as follows:

data_bag_item(bag_name, item, secret)

where secret is the secret used to load an encrypted data bag. If secret is not specified, the chef-client looks for a secret at the path specified by the encrypted_data_bag_secret setting in the client.rb file.

Examples

The following examples show how the data_bag_item method can be used in a recipe.

Get a data bag, and then iterate through each data bag item

data_bag('users') #=> ['sandy', 'jill']

Iterate over the contents of the data bag to get the associated data_bag_item:

data_bag('users').each do |user|
  data_bag_item('users', user)
end

The id for each data bag item will be returned as a string.

Use the contents of a data bag in a recipe

The following example shows how to use the data_bag and data_bag_item methods in a recipe, also using a data bag named sea-power):

package 'sea-power' do
  action :install
end

directory node['sea-power']['base_path'] do
  # attributes for owner, group, mode
end

gale_warnings = data_bag('sea-power').map do |viking_north|
  data_bag_item('sea-power', viking_north)['source']
end

template '/etc/seattle/power.list' do
  source 'seattle-power.erb'
  # attributes for owner, group, mode
  variables(
    :base_path => node['sea-power']['base_path'],
    # more variables
    :repo_location => gale_warnings
  )
end

For a more complete version of the previous example, see the default recipe in the https://github.com/hw-cookbooks/apt-mirror community cookbook.

platform?

Use the platform? method to ensure that certain actions are run for specific platform. The platform? method will return true if one of the listed parameters matches the node['platform'] attribute that is detected by Ohai during every chef-client run.

The syntax for the platform? method is as follows:

platform?('parameter', 'parameter')

where:

• parameter is a comma-separated list, each specifying a platform, such as Red Hat, CentOS, or Fedora
• platform? method is typically used with an if, elseif, or case statement that contains Ruby code that is specific for the platform, if detected

Parameters

The following parameters can be used with this method:

Parameter	Platforms
aix	AIX. All platform variants of AIX return aix.
arch	Arch Linux
debian	Debian, Linux Mint, Ubuntu
fedora	Fedora
freebsd	FreeBSD. All platform variants of FreeBSD return freebsd.
gentoo	Gentoo
hpux	HP-UX. All platform variants of HP-UX return hpux.
mac_os_x	Mac OS X
netbsd	NetBSD. All platform variants of NetBSD return netbsd.
openbsd	OpenBSD. All platform variants of OpenBSD return openbsd.
slackware	Slackware
solaris	Solaris. For Solaris-related platforms, the platform_family method does not support the Solaris platform family and will default back to platform_family = platform. For example, if the platform is OmniOS, the platform_family is omnios, if the platform is SmartOS, the platform_family is smartos, and so on. All platform variants of Solaris return solaris.
suse	openSUSE, SUSE Enterprise Linux Server.
windows	Microsoft Windows. All platform variants of Microsoft Windows return windows.

For example:

platform?('debian')

or:

platform?('rhel', 'debian')

Examples

The following example shows how the platform? method can be used in a recipe.

Use an if statement with the platform recipe DSL method

The following example shows how an if statement can be used with the platform? method in the Recipe DSL to run code specific to Microsoft Windows. The code is defined using the ruby_block resource:

# the following code sample comes from the ``client`` recipe
# in the following cookbook: https://github.com/chef-cookbooks/mysql

if platform?('windows')
  ruby_block 'copy libmysql.dll into ruby path' do
    block do
      require 'fileutils'
      FileUtils.cp "#{node['mysql']['client']['lib_dir']}\\libmysql.dll",
        node['mysql']['client']['ruby_dir']
    end
    not_if { File.exist?("#{node['mysql']['client']['ruby_dir']}\\libmysql.dll") }
  end
end

platform_family?

Use the platform_family? method to ensure that certain actions are run for specific platform family. The platform_family? method will return true if one of the listed parameters matches the node['platform_family'] attribute that is detected by Ohai during every chef-client run.

The syntax for the platform_family? method is as follows:

platform_family?('parameter', 'parameter')

where:

• 'parameter' is a comma-separated list, each specifying a platform family, such as Debian, or Red Hat Enterprise Linux
• platform_family? method is typically used with an if, elseif, or case statement that contains Ruby code that is specific for the platform family, if detected

For example:

if platform_family?('rhel')
  # do RHEL things
end

or:

if platform_family?('debian', 'rhel')
  # do things on debian and rhel families
end

For example:

platform_family?('gentoo')

or:

platform_family?('slackware', 'suse', 'arch')

Examples

The following examples show how the platform_family? method can be used in a recipe.

Use a specific binary for a specific platform

The following is an example of using the platform_family? method in the Recipe DSL to create a variable that can be used with other resources in the same recipe. In this example, platform_family? is being used to ensure that a specific binary is used for a specific platform before using the remote_file resource to download a file from a remote location, and then using the execute resource to install that file by running a command.

if platform_family?('rhel')
  pip_binary = '/usr/bin/pip'
else
  pip_binary = '/usr/local/bin/pip'
end

remote_file "#{Chef::Config[:file_cache_path]}/distribute_setup.py" do
  source 'http://python-distribute.org/distribute_setup.py'
  mode '0755'
  not_if { File.exist?(pip_binary) }
end

execute 'install-pip' do
  cwd Chef::Config[:file_cache_path]
  command <<-EOF
    # command for installing Python goes here
    EOF
  not_if { File.exist?(pip_binary) }
end

where a command for installing Python might look something like:

#{node['python']['binary']} distribute_setup.py
#{::File.dirname(pip_binary)}/easy_install pip

reboot_pending?

Use the reboot_pending? method to test if a node needs a reboot, or is expected to reboot. reboot_pending? returns true when the node needs a reboot.

The syntax for the reboot_pending? method is as follows:

reboot_pending?

recipe_name

Use the recipe_name method to return the name of a recipe.

The syntax for the recipe_name method is as follows:

recipe_name

This method is often used as part of a log entry. For example:

Chef::Log.info('I am a message from the #{recipe_name} recipe in the #{cookbook_name} cookbook.')

resources

Use the resources method to look up a resource in the resource collection. The resources method returns the value for the resource that it finds in the resource collection. The preferred syntax for the resources method is as follows:

resources('resource_type[resource_name]')

but the following syntax can also be used:

resources(:resource_type => 'resource_name')

where in either approach resource_type is the name of a resource and resource_name is the name of a resource that can be configured by the chef-client.

The resources method can be used to modify a resource later on in a recipe. For example:

file '/etc/hosts' do
  content '127.0.0.1 localhost.localdomain localhost'
end

and then later in the same recipe, or elsewhere:

f = resources('file[/etc/hosts]')
f.mode '0644'

where file is the type of resource, /etc/hosts is the name, and f.mode is used to set the mode property on the file resource.

search

Search indexes allow queries to be made for any type of data that is indexed by the Chef server, including data bags (and data bag items), environments, nodes, and roles. A defined query syntax is used to support search patterns like exact, wildcard, range, and fuzzy. A search is a full-text query that can be done from several locations, including from within a recipe, by using the search subcommand in knife, the search method in the Recipe DSL, the search box in the Chef management console, and by using the /search or /search/INDEX endpoints in the Chef server API. The search engine is based on Apache Solr and is run from the Chef server.

Use the search method to perform a search query against the Chef server from within a recipe.

The syntax for the search method is as follows:

search(:index, 'query')

where:

• :index is of name of the index on the Chef server against which the search query will run: :client, :data_bag_name, :environment, :node, and :role
• 'query' is a valid search query against an object on the Chef server (see below for more information about how to build the query)

For example, using the results of a search query within a variable:

webservers = search(:node, 'role:webserver')

and then using the results of that query to populate a template:

template '/tmp/list_of_webservers' do
  source 'list_of_webservers.erb'
  variables(:webservers => webservers)
end

Query Syntax

A search query is comprised of two parts: the key and the search pattern. A search query has the following syntax:

key:search_pattern

where key is a field name that is found in the JSON description of an indexable object on the Chef server (a role, node, client, environment, or data bag) and search_pattern defines what will be searched for, using one of the following search patterns: exact, wildcard, range, or fuzzy matching. Both key and search_pattern are case-sensitive; key has limited support for multiple character wildcard matching using an asterisk (“*”) (and as long as it is not the first character).

Keys

A field name/description pair is available in the JSON object. Use the field name when searching for this information in the JSON object. Any field that exists in any JSON description for any role, node, chef-client, environment, or data bag can be searched.

Nested Fields

A nested field appears deeper in the JSON data structure. For example, information about a network interface might be several layers deep: node[:network][:interfaces][:en1]. When nested fields are present in a JSON structure, the chef-client will extract those nested fields to the top-level, flattening them into compound fields that support wildcard search patterns.

By combining wildcards with range-matching patterns and wildcard queries, it is possible to perform very powerful searches, such as using the vendor part of the MAC address to find every node that has a network card made by the specified vendor.

Consider the following snippet of JSON data:

{"network":
  [
  //snipped...
    "interfaces",
      {"en1": {
        "number": "1",
        "flags": [
          "UP",
          "BROADCAST",
          "SMART",
          "RUNNING",
          "SIMPLEX",
          "MULTICAST"
        ],
        "addresses": {
          "fe80::fa1e:dfff:fed8:63a2": {
            "scope": "Link",
            "prefixlen": "64",
            "family": "inet6"
          },
          "f8:1e:df:d8:63:a2": {
            "family": "lladdr"
          },
          "192.168.0.195": {
            "netmask": "255.255.255.0",
            "broadcast": "192.168.0.255",
            "family": "inet"
          }
        },
        "mtu": "1500",
        "media": {
          "supported": {
            "autoselect": {
              "options": [

              ]
            }
          },
          "selected": {
            "autoselect": {
              "options": [

              ]
            }
          }
        },
        "type": "en",
        "status": "active",
        "encapsulation": "Ethernet"
      },
  //snipped...

Before this data is indexed on the Chef server, the nested fields are extracted into the top level, similar to:

"broadcast" => "192.168.0.255",
"flags"     => ["UP", "BROADCAST", "SMART", "RUNNING", "SIMPLEX", "MULTICAST"]
"mtu"       => "1500"

which allows searches like the following to find data that is present in this node:

node "broadcast:192.168.0.*"

or:

node "mtu:1500"

or:

node "flags:UP"

This data is also flattened into various compound fields, which follow the same pattern as the JSON hierarchy and use underscores (_) to separate the levels of data, similar to:

# ...snip...
"network_interfaces_en1_addresses_192.168.0.195_broadcast" => "192.168.0.255",
"network_interfaces_en1_addresses_fe80::fa1e:tldr_family"  => "inet6",
"network_interfaces_en1_addresses"                         => ["fe80::fa1e:tldr","f8:1e:df:tldr","192.168.0.195"]
# ...snip...

which allows searches like the following to find data that is present in this node:

node "network_interfaces_en1_addresses:192.168.0.195"

This flattened data structure also supports using wildcard compound fields, which allow searches to omit levels within the JSON data structure that are not important to the search query. In the following example, an asterisk (*) is used to show where the wildcard can exist when searching for a nested field:

"network_interfaces_*_flags"     => ["UP", "BROADCAST", "SMART", "RUNNING", "SIMPLEX", "MULTICAST"]
"network_interfaces_*_addresses" => ["fe80::fa1e:dfff:fed8:63a2", "192.168.0.195", "f8:1e:df:d8:63:a2"]
"network_interfaces_en0_media_*" => ["autoselect", "none", "1000baseT", "10baseT/UTP", "100baseTX"]
"network_interfaces_en1_*"       => ["1", "UP", "BROADCAST", "SMART", "RUNNING", "SIMPLEX", "MULTICAST",
                                     "fe80::fa1e:dfff:fed8:63a2", "f8:1e:df:d8:63:a2", "192.168.0.195",
                                     "1500", "supported", "selected", "en", "active", "Ethernet"]

For each of the wildcard examples above, the possible values are shown contained within the brackets. When running a search query, the query syntax for wildcards is to simply omit the name of the node (while preserving the underscores), similar to:

network_interfaces__flags

This query will search within the flags node, within the JSON structure, for each of UP, BROADCAST, SMART, RUNNING, SIMPLEX, and MULTICAST.

Patterns

A search pattern is a way to fine-tune search results by returning anything that matches some type of incomplete search query. There are four types of search patterns that can be used when searching the search indexes on the Chef server: exact, wildcard, range, and fuzzy.

Exact Match

An exact matching search pattern is used to search for a key with a name that exactly matches a search query. If the name of the key contains spaces, quotes must be used in the search pattern to ensure the search query finds the key. The entire query must also be contained within quotes, so as to prevent it from being interpreted by Ruby or a command shell. The best way to ensure that quotes are used consistently is to quote the entire query using single quotes (‘ ‘) and a search pattern with double quotes (” ”).

Wildcard Match

A wildcard matching search pattern is used to query for substring matches that replace zero (or more) characters in the search pattern with anything that could match the replaced character. There are two types of wildcard searches:

• A question mark (?) can be used to replace exactly one character (as long as that character is not the first character in the search pattern)
• An asterisk (*) can be used to replace any number of characters (including zero)

Range Match

A range matching search pattern is used to query for values that are within a range defined by upper and lower boundaries. A range matching search pattern can be inclusive or exclusive of the boundaries. Use square brackets (“[ ]”) to denote inclusive boundaries and curly braces (“{ }”) to denote exclusive boundaries and with the following syntax:

boundary TO boundary

where TO is required (and must be capitalized).

Fuzzy Match

A fuzzy matching search pattern is used to search based on the proximity of two strings of characters. An (optional) integer may be used as part of the search query to more closely define the proximity. A fuzzy matching search pattern has the following syntax:

"search_query"~edit_distance

where search_query is the string that will be used during the search and edit_distance is the proximity. A tilde (“~”) is used to separate the edit distance from the search query.

Operators

An operator can be used to ensure that certain terms are included in the results, are excluded from the results, or are not included even when other aspects of the query match. Searches can use the following operators:

Operator	Description
AND	Use to find a match when both terms exist.
OR	Use to find a match if either term exists.
NOT	Use to exclude the term after NOT from the search results.

Special Characters

A special character can be used to fine-tune a search query and to increase the accuracy of the search results. The following characters can be included within the search query syntax, but each occurrence of a special character must be escaped with a backslash (\):

+  -  &&  | |  !  ( )  { }  [ ]  ^  "  ~  *  ?  :  \

For example:

\(1\+1\)\:2

Examples

The following examples show how the search method can be used in a recipe.

Use the search recipe DSL method to find users

The following example shows how to use the search method in the Recipe DSL to search for users:

#  the following code sample comes from the openvpn cookbook: https://github.com/chef-cookbooks/openvpn

search("users", "*:*") do |u|
  execute "generate-openvpn-#{u['id']}" do
    command "./pkitool #{u['id']}"
    cwd '/etc/openvpn/easy-rsa'
    environment(
      'EASY_RSA' => '/etc/openvpn/easy-rsa',
      'KEY_CONFIG' => '/etc/openvpn/easy-rsa/openssl.cnf',
      'KEY_DIR' => node['openvpn']['key_dir'],
      'CA_EXPIRE' => node['openvpn']['key']['ca_expire'].to_s,
      'KEY_EXPIRE' => node['openvpn']['key']['expire'].to_s,
      'KEY_SIZE' => node['openvpn']['key']['size'].to_s,
      'KEY_COUNTRY' => node['openvpn']['key']['country'],
      'KEY_PROVINCE' => node['openvpn']['key']['province'],
      'KEY_CITY' => node['openvpn']['key']['city'],
      'KEY_ORG' => node['openvpn']['key']['org'],
      'KEY_EMAIL' => node['openvpn']['key']['email']
    )
    not_if { File.exist?("#{node['openvpn']['key_dir']}/#{u['id']}.crt") }
  end

  %w{ conf ovpn }.each do |ext|
    template "#{node['openvpn']['key_dir']}/#{u['id']}.#{ext}" do
      source 'client.conf.erb'
      variables :username => u['id']
    end
  end

  execute "create-openvpn-tar-#{u['id']}" do
    cwd node['openvpn']['key_dir']
    command <<-EOH
      tar zcf #{u['id']}.tar.gz \
      ca.crt #{u['id']}.crt #{u['id']}.key \
      #{u['id']}.conf #{u['id']}.ovpn \
    EOH
    not_if { File.exist?("#{node['openvpn']['key_dir']}/#{u['id']}.tar.gz") }
  end
end

where

• the search will use both of the execute resources, unless the condition specified by the not_if commands are met
• the environments property in the first execute resource is being used to define values that appear as variables in the OpenVPN configuration
• the template resource tells the chef-client which template to use

tag, tagged?, untag

A tag is a custom description that is applied to a node. A tag, once applied, can be helpful when managing nodes using knife or when building recipes by providing alternate methods of grouping similar types of information.

Tags can be added and removed. Machines can be checked to see if they already have a specific tag. To use tags in your recipe simply add the following:

tag('mytag')

To test if a machine is tagged, add the following:

tagged?('mytag')

to return true or false. tagged? can also use an array as an argument.

To remove a tag:

untag('mytag')

For example:

tag('machine')

if tagged?('machine')
   Chef::Log.info('Hey I'm #{node[:tags]}')
end

untag('machine')

if not tagged?('machine')
   Chef::Log.info('I has no tagz')
end

Will return something like this:

[Thu, 22 Jul 2010 18:01:45 +0000] INFO: Hey I'm machine
[Thu, 22 Jul 2010 18:01:45 +0000] INFO: I has no tagz

value_for_platform

Use the value_for_platform method in a recipe to select a value based on the node['platform'] and node['platform_version'] attributes. These values are detected by Ohai during every chef-client run.

The syntax for the value_for_platform method is as follows:

value_for_platform( ['platform', ...] => { 'version' => 'value' } )

where:

• 'platform', ... is a comma-separated list of platforms, such as Red Hat, openSUSE, or Fedora
• version specifies the version of that platform
• Version constraints—>, <, >=, <=, ~>—may be used with version; an exception is raised if two version constraints match; an exact match will always take precedence over a match made from a version constraint
• value specifies the value that will be used if the node’s platform matches the value_for_platform method

When each value only has a single platform, use the following syntax:

value_for_platform(
  'platform' => { 'version' => 'value' },
  'platform' => { 'version' => 'value' },
  'platform' => 'value'
)

When each value has more than one platform, the syntax changes to:

value_for_platform(
  ['platform', 'platform', ... ] => {
    'version' => 'value'
  },
)

Operators

The following operators may be used:

Operator	Description
=	equal to
>	greater than
<	less than
>=	greater than or equal to; also known as “optimistically greater than”, or “optimistic”
<=	less than or equal to
~>	approximately greater than; also known as “pessimistically greater than”, or “pessimistic”

Examples

The following example will set package_name to httpd for the Red Hat platform and to apache2 for the Debian platform:

package_name = value_for_platform(
  ['centos', 'redhat', 'suse', 'fedora' ] => {
    'default' => 'httpd'
  },
  ['ubuntu', 'debian'] => {
    'default' => 'apache2'
  }
)

The following example will set package to apache-couchdb for OpenBSD platforms, dev-db/couchdb for Gentoo platforms, and couchdb for all other platforms:

package = value_for_platform(
  'openbsd' => { 'default' => 'apache-couchdb' },
  'gentoo' => { 'default' => 'dev-db/couchdb' },
  'default' => 'couchdb'
)

The following example shows using version constraints to specify a value based on the version:

value_for_platform(
  'os1' => { '< 1.0' => 'less than 1.0',
             '~> 2.0' => 'version 2.x',
             '>= 3.0' => 'version 3.0',
             '3.0.1' => '3.0.1 will always use this value' }
)

value_for_platform_family

Use the value_for_platform_family method in a recipe to select a value based on the node['platform_family'] attribute. This value is detected by Ohai during every chef-client run.

The syntax for the value_for_platform_family method is as follows:

value_for_platform_family( 'platform_family' => { 'version' => 'value' }, ... )

where:

• 'platform_family' => { 'version' => 'value' }, ... is a comma-separated list of platforms, such as Fedora, openSUSE, or Red Hat Enterprise Linux
• value specifies the value that will be used if the node’s platform family matches the value_for_platform_family method

When each value only has a single platform, use the following syntax:

value_for_platform_family(
  'platform_family' => { 'version' => 'value' },
  'platform_family' => { 'version' => 'value' },
  'platform_family' => 'value'
)

When each value has more than one platform, the syntax changes to:

value_for_platform_family(
  ['platform_family', 'platform_family', 'platform_family', 'platform_family' ] => 'value',
  ['platform_family', 'platform_family'] => 'value',
  'default' => 'value'
)

The following example will set package to httpd-devel for the Red Hat Enterprise Linux, Fedora, and openSUSE platforms and to apache2-dev for the Debian platform:

package = value_for_platform_family(
  ['rhel', 'fedora', 'suse'] => 'httpd-devel',
    'debian' => 'apache2-dev'
)

Windows Platform

Six methods are present in the Recipe DSL to help verify the registry during a chef-client run on the Microsoft Windows platform—registry_data_exists?, registry_get_subkeys, registry_get_values, registry_has_subkeys?, registry_key_exists?, and registry_value_exists?—these helpers ensure the powershell_script resource is idempotent.

registry_data_exists?

Use the registry_data_exists? method to find out if a Microsoft Windows registry key contains the specified data of the specified type under the value.

The syntax for the registry_data_exists? method is as follows:

registry_data_exists?(
  KEY_PATH,
  { :name => 'NAME', :type => TYPE, :data => DATA },
  ARCHITECTURE
)

where:

• KEY_PATH is the path to the registry key value. The path must include the registry hive, which can be specified either as its full name or as the 3- or 4-letter abbreviation. For example, both HKLM\SECURITY and HKEY_LOCAL_MACHINE\SECURITY are both valid and equivalent. The following hives are valid: HKEY_LOCAL_MACHINE, HKLM, HKEY_CURRENT_CONFIG, HKCC, HKEY_CLASSES_ROOT, HKCR, HKEY_USERS, HKU, HKEY_CURRENT_USER, and HKCU.
• { :name => 'NAME', :type => TYPE, :data => DATA } is a hash that contains the expected name, type, and data of the registry key value
• :type represents the values available for registry keys in Microsoft Windows. Use :binary for REG_BINARY, :string for REG_SZ, :multi_string for REG_MULTI_SZ, :expand_string for REG_EXPAND_SZ, :dword for REG_DWORD, :dword_big_endian for REG_DWORD_BIG_ENDIAN, or :qword for REG_QWORD.
• ARCHITECTURE is one of the following values: :x86_64, :i386, or :machine. In order to read or write 32-bit registry keys on 64-bit machines running Microsoft Windows, the architecture property must be set to :i386. The :x86_64 value can be used to force writing to a 64-bit registry location, but this value is less useful than the default (:machine) because the chef-client returns an exception if :x86_64 is used and the machine turns out to be a 32-bit machine (whereas with :machine, the chef-client is able to access the registry key on the 32-bit machine).

This method will return true or false.

registry_get_subkeys

Use the registry_get_subkeys method to get a list of registry key values that are present for a Microsoft Windows registry key.

The syntax for the registry_get_subkeys method is as follows:

subkey_array = registry_get_subkeys(KEY_PATH, ARCHITECTURE)

where:

• KEY_PATH is the path to the registry key. The path must include the registry hive, which can be specified either as its full name or as the 3- or 4-letter abbreviation. For example, both HKLM\SECURITY and HKEY_LOCAL_MACHINE\SECURITY are both valid and equivalent. The following hives are valid: HKEY_LOCAL_MACHINE, HKLM, HKEY_CURRENT_CONFIG, HKCC, HKEY_CLASSES_ROOT, HKCR, HKEY_USERS, HKU, HKEY_CURRENT_USER, and HKCU.
• ARCHITECTURE is one of the following values: :x86_64, :i386, or :machine. In order to read or write 32-bit registry keys on 64-bit machines running Microsoft Windows, the architecture property must be set to :i386. The :x86_64 value can be used to force writing to a 64-bit registry location, but this value is less useful than the default (:machine) because the chef-client returns an exception if :x86_64 is used and the machine turns out to be a 32-bit machine (whereas with :machine, the chef-client is able to access the registry key on the 32-bit machine).

This returns an array of registry key values.

registry_get_values

Use the registry_get_values method to get the registry key values (name, type, and data) for a Microsoft Windows registry key.

The syntax for the registry_get_values method is as follows:

subkey_array = registry_get_values(KEY_PATH, ARCHITECTURE)

where:

• KEY_PATH is the path to the registry key. The path must include the registry hive, which can be specified either as its full name or as the 3- or 4-letter abbreviation. For example, both HKLM\SECURITY and HKEY_LOCAL_MACHINE\SECURITY are both valid and equivalent. The following hives are valid: HKEY_LOCAL_MACHINE, HKLM, HKEY_CURRENT_CONFIG, HKCC, HKEY_CLASSES_ROOT, HKCR, HKEY_USERS, HKU, HKEY_CURRENT_USER, and HKCU.
• ARCHITECTURE is one of the following values: :x86_64, :i386, or :machine. In order to read or write 32-bit registry keys on 64-bit machines running Microsoft Windows, the architecture property must be set to :i386. The :x86_64 value can be used to force writing to a 64-bit registry location, but this value is less useful than the default (:machine) because the chef-client returns an exception if :x86_64 is used and the machine turns out to be a 32-bit machine (whereas with :machine, the chef-client is able to access the registry key on the 32-bit machine).

This returns an array of registry key values.

registry_has_subkeys?

Use the registry_has_subkeys? method to find out if a Microsoft Windows registry key has one (or more) values.

The syntax for the registry_has_subkeys? method is as follows:

registry_has_subkeys?(KEY_PATH, ARCHITECTURE)

where:

• KEY_PATH is the path to the registry key. The path must include the registry hive, which can be specified either as its full name or as the 3- or 4-letter abbreviation. For example, both HKLM\SECURITY and HKEY_LOCAL_MACHINE\SECURITY are both valid and equivalent. The following hives are valid: HKEY_LOCAL_MACHINE, HKLM, HKEY_CURRENT_CONFIG, HKCC, HKEY_CLASSES_ROOT, HKCR, HKEY_USERS, HKU, HKEY_CURRENT_USER, and HKCU.
• ARCHITECTURE is one of the following values: :x86_64, :i386, or :machine. In order to read or write 32-bit registry keys on 64-bit machines running Microsoft Windows, the architecture property must be set to :i386. The :x86_64 value can be used to force writing to a 64-bit registry location, but this value is less useful than the default (:machine) because the chef-client returns an exception if :x86_64 is used and the machine turns out to be a 32-bit machine (whereas with :machine, the chef-client is able to access the registry key on the 32-bit machine).

This method will return true or false.

registry_key_exists?

Use the registry_key_exists? method to find out if a Microsoft Windows registry key exists at the specified path.

The syntax for the registry_key_exists? method is as follows:

registry_key_exists?(KEY_PATH, ARCHITECTURE)

where:

• KEY_PATH is the path to the registry key. The path must include the registry hive, which can be specified either as its full name or as the 3- or 4-letter abbreviation. For example, both HKLM\SECURITY and HKEY_LOCAL_MACHINE\SECURITY are both valid and equivalent. The following hives are valid: HKEY_LOCAL_MACHINE, HKLM, HKEY_CURRENT_CONFIG, HKCC, HKEY_CLASSES_ROOT, HKCR, HKEY_USERS, HKU, HKEY_CURRENT_USER, and HKCU.
• ARCHITECTURE is one of the following values: :x86_64, :i386, or :machine. In order to read or write 32-bit registry keys on 64-bit machines running Microsoft Windows, the architecture property must be set to :i386. The :x86_64 value can be used to force writing to a 64-bit registry location, but this value is less useful than the default (:machine) because the chef-client returns an exception if :x86_64 is used and the machine turns out to be a 32-bit machine (whereas with :machine, the chef-client is able to access the registry key on the 32-bit machine).

This method will return true or false. (Any registry key values that are associated with this registry key are ignored.)

registry_value_exists?

Use the registry_value_exists? method to find out if a registry key value exists. Use registry_data_exists? to test for the type and data of a registry key value.

The syntax for the registry_value_exists? method is as follows:

registry_value_exists?(
  KEY_PATH,
  { :name => 'NAME' },
  ARCHITECTURE
)

where:

• KEY_PATH is the path to the registry key. The path must include the registry hive, which can be specified either as its full name or as the 3- or 4-letter abbreviation. For example, both HKLM\SECURITY and HKEY_LOCAL_MACHINE\SECURITY are both valid and equivalent. The following hives are valid: HKEY_LOCAL_MACHINE, HKLM, HKEY_CURRENT_CONFIG, HKCC, HKEY_CLASSES_ROOT, HKCR, HKEY_USERS, HKU, HKEY_CURRENT_USER, and HKCU.
• { :name => 'NAME' } is a hash that contains the name of the registry key value; if either :type or :value are specified in the hash, they are ignored
• :type represents the values available for registry keys in Microsoft Windows. Use :binary for REG_BINARY, :string for REG_SZ, :multi_string for REG_MULTI_SZ, :expand_string for REG_EXPAND_SZ, :dword for REG_DWORD, :dword_big_endian for REG_DWORD_BIG_ENDIAN, or :qword for REG_QWORD.
• ARCHITECTURE is one of the following values: :x86_64, :i386, or :machine. In order to read or write 32-bit registry keys on 64-bit machines running Microsoft Windows, the architecture property must be set to :i386. The :x86_64 value can be used to force writing to a 64-bit registry location, but this value is less useful than the default (:machine) because the chef-client returns an exception if :x86_64 is used and the machine turns out to be a 32-bit machine (whereas with :machine, the chef-client is able to access the registry key on the 32-bit machine).

This method will return true or false.

Helpers

A recipe can define specific behaviors for specific Microsoft Windows platform versions by using a series of helper methods. To enable these helper methods, add the following to a recipe:

require 'chef/win32/version'

Then declare a variable using the Chef::ReservedNames::Win32::Version class:

variable_name = Chef::ReservedNames::Win32::Version.new

And then use this variable to define specific behaviors for specific Microsoft Windows platform versions. For example:

if variable_name.helper_name?
  # Ruby code goes here, such as
  resource_name do
    # resource block
  end

elsif variable_name.helper_name?
  # Ruby code goes here
  resource_name do
    # resource block for something else
  end

else variable_name.helper_name?
  # Ruby code goes here, such as
  log 'log entry' do
    level :level
  end

end

The following Microsoft Windows platform-specific helpers can be used in recipes:

Helper	Description
cluster?	Use to test for a Cluster SKU (Windows Server 2003 and later).
core?	Use to test for a Core SKU (Windows Server 2003 and later).
datacenter?	Use to test for a Datacenter SKU.
marketing_name	Use to display the marketing name for a Microsoft Windows platform.
windows_7?	Use to test for Windows 7.
windows_8?	Use to test for Windows 8.
windows_8_1?	Use to test for Windows 8.1.
windows_2000?	Use to test for Windows 2000.
windows_home_server?	Use to test for Windows Home Server.
windows_server_2003?	Use to test for Windows Server 2003.
windows_server_2003_r2?	Use to test for Windows Server 2003 R2.
windows_server_2008?	Use to test for Windows Server 2008.
windows_server_2008_r2?	Use to test for Windows Server 2008 R2.
windows_server_2012?	Use to test for Windows Server 2012.
windows_server_2012_r2?	Use to test for Windows Server 2012 R2.
windows_vista?	Use to test for Windows Vista.
windows_xp?	Use to test for Windows XP.

The following example installs Windows PowerShell 2.0 on systems that do not already have it installed. Microsoft Windows platform helper methods are used to define specific behaviors for specific platform versions:

case node['platform']
when 'windows'

  require 'chef/win32/version'
  windows_version = Chef::ReservedNames::Win32::Version.new

  if (windows_version.windows_server_2008_r2? || windows_version.windows_7?) && windows_version.core?

    windows_feature 'NetFx2-ServerCore' do
      action :install
    end
    windows_feature 'NetFx2-ServerCore-WOW64' do
      action :install
      only_if { node['kernel']['machine'] == 'x86_64' }
    end

  elsif windows_version.windows_server_2008? || windows_version.windows_server_2003_r2? ||
      windows_version.windows_server_2003? || windows_version.windows_xp?

    if windows_version.windows_server_2008?
      windows_feature 'NET-Framework-Core' do
        action :install
      end

    else
      windows_package 'Microsoft .NET Framework 2.0 Service Pack 2' do
        source node['ms_dotnet2']['url']
        checksum node['ms_dotnet2']['checksum']
        installer_type :custom
        options '/quiet /norestart'
        action :install
      end
    end
  else
    log '.NET Framework 2.0 is already enabled on this version of Windows' do
      level :warn
    end
  end
else
  log '.NET Framework 2.0 cannot be installed on platforms other than Windows' do
    level :warn
  end
end

The previous example is from the ms_dotnet2 cookbook, created by community member juliandunn.