Chef Infra Language: Checking Platforms

platform?

Use the platform? helper method to ensure that certain actions are run for specific platforms. 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 Infra 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, elsif, or case statement that contains Ruby code that is specific for the platform, if detected

platform Values

Examples

Installing the cron package on Debian systems

package 'cron' if platform?('debian')

Deleting a file on Red Hat and Debian systems

if platform?('redhat', 'debian')
  file '/etc/some_config' do
    action :remove
  end
end

Installing the correct Firefox package

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

if platform?('windows')
  chocolatey_package 'firefox'
else
  package 'firefox'
end

platform_family?

Use the platform_family? method to ensure that certain actions are run for specific platform families. The platform_family? method will return true if one of the listed parameters matches the node['platform_family'] attribute that are detected by Ohai during every Chef Infra 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, elsif, or case statement that contains Ruby code that is specific for the platform family, if detected

platform_family Values

Examples

For example:

platform_family?('gentoo')

or:

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

Use a Specific Binary For a Specific Platform

The following is an example of using the platform_family? method in the Chef Infra Language 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

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 Infra 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:

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' => 'greater than or equal to 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 Infra Client run.

The syntax for the value_for_platform_family method is as follows:

value_for_platform_family( 'platform_family' => 'value', ... )

where:

• 'platform_family' => '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' => 'value',
  'platform_family' => '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'
)