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AWS OpsWorks
User Guide (API Version 2013-02-18)

Recipes

Recipes are Ruby applications that define a system's configuration. They install packages, create configuration files from templates, execute shell commands, create files and directories, and so on. You typically have AWS OpsWorks Stacks execute recipes automatically when a lifecycle event occurs on the instance but you can also run them explicitly at any time by using the Execute Recipes stack command. For more information, see About Recipes.

A recipe typically consists largely of a series of resources, each of which represents the desired state of an aspect of the system. Each resource includes a set of attributes that define the desired state and specify what action is to be taken. Chef associates each resource with an appropriate provider that performs the action. For more information, see Resources and Providers Reference.

A package resource helps you manage software packages on Linux instances. The following example installs the Apache package.

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... package 'apache2' do case node[:platform] when 'centos','redhat','fedora','amazon' package_name 'httpd' when 'debian','ubuntu' package_name 'apache2' end action :install end ...

Chef uses the appropriate package provider for the platform. Resource attributes are often just assigned a value, but you can use Ruby logical operations to perform conditional assignments. The example uses a case operator, which uses node[:platform] to identify the instance's operating system and sets the package_name attribute accordingly. You can insert attributes into a recipe by using the standard Chef node syntax and Chef replaces it with the associated value. You can use any attribute in the node object, not just your cookbook's attributes.

After determining the appropriate package name, the code segment ends with an install action, which installs the package. Other actions for this resource include upgrade and remove. For more information, see package.

It is often useful to break complex installation and configuration tasks into one or more subtasks, each implemented as a separate recipe, and have your primary recipe run them at the appropriate time. The following example shows the line of code that follows the preceding example:

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include_recipe 'apache2::service'

To have a recipe execute a child recipe, use the include_recipe keyword, followed by the recipe name. Recipes are identified by using the standard Chef CookbookName::RecipeName syntax, where RecipeName omits the .rb extension.

Note

An include_recipe statement effectively executes the recipe at that point in the primary recipe. However, what actually happens is that Chef replaces each include_recipe statement with the specified recipe's code before it executes the primary recipe.

A directory resource represents a directory, such as the one that is to contain a package's files. The following default.rb resource creates a Linux log directory.

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directory node[:apache][:log_dir] do mode 0755 action :create end

The log directory is defined in one of the cookbook's attribute files. The resource specifies the directory's mode as 0755, and uses a create action to create the directory. For more information, see directory. You can also use this resource with Windows instances.

The execute resource represents commands, such as shell commands or scripts. The following example generates module.load files.

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execute 'generate-module-list' do if node[:kernel][:machine] == 'x86_64' libdir = 'lib64' else libdir = 'lib' end command "/usr/local/bin/apache2_module_conf_generate.pl /usr/#{libdir}/httpd/modules /etc/httpd/mods-available" action :run end

The resource first determines the CPU type. [:kernel][:machine] is another of the automatic attributes that Chef generates to represent various system properties, the CPU type in this case. It then specifies the command, a Perl script and uses a run action to run the script, which generates the module.load files. For more information, see execute.

A template resource represents a file—typically a configuration file—that is to be generated from one of the cookbook's template files. The following example creates an httpd.conf configuration file from the apache2.conf.erb template that was discussed in Templates.

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template 'apache2.conf' do case node[:platform] when 'centos','redhat','fedora','amazon' path "#{node[:apache][:dir]}/conf/httpd.conf" when 'debian','ubuntu' path "#{node[:apache][:dir]}/apache2.conf" end source 'apache2.conf.erb' owner 'root' group 'root' mode 0644 notifies :restart, resources(:service => 'apache2') end

The resource determines the generated file's name and location based on the instance's operating system. It then specifies apache2.conf.erb as the template to be used to generate the file and sets the file's owner, group, and mode. It runs the notify action to notify the service resource that represents the Apache server to restart the server. For more information, see template.