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

Using an External Cookbook on a Linux Instance: Berkshelf

Note

Berkshelf is available only for Chef 11.10 Linux stacks.

Before you start implementing a cookbook, check out Chef Community Cookbooks, which contains cookbooks that have been created by members of the Chef community for a wide variety of purposes. Many of these cookbooks can be used with AWS OpsWorks Stacks without modification, so you might able to take advantage of them for some of your tasks instead of implementing all the code yourself.

To use an external cookbook on an instance, you need a way to install it and manage any dependencies. The preferred approach is to implement a cookbook that supports a dependency manager named Berkshelf. Berkshelf works on Amazon EC2 instances, including AWS OpsWorks Stacks instances, but it is also designed to work with Test Kitchen and Vagrant. However, the usage on Vagrant is a bit different than with AWS OpsWorks Stacks, so this topic includes examples for both platforms. For more information on how to use Berkshelf, see Berkshelf.

Using Berkshelf with Test Kitchen and Vagrant

This example shows how to use Berkshelf to install the getting-started community cookbook and execute its recipe, which installs a brief text file in your home directory on the instance.

To install Berkshelf and initialize a cookbook

  1. On your workstation, install the Berkshelf gem, as follows.

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    gem install berkshelf

    Depending on your workstation, this command might require sudo, or you can also use a Ruby environment manager such as RVM. To verify that Berkshelf was successfully installed, run berks --version.

  2. The cookbook for this topic is named external_cookbook. You can use Berkshelf to create an initialized cookbook instead of the manual approach that the previous topics have taken. To do so, navigate to the opsworks_cookbooks directory and run the following command.

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    berks cookbook external_cookbook

    The command creates the external_cookbook directory and several standard Chef and Test Kitchen subdirectories, including recipes and test. The command also creates default versions of a number of standard files, including the following:

    • metadata.rb

    • Configuration files for Vagrant, Test Kitchen, and Berkshelf

    • An empty default.rb recipe in the recipes directory

    Note

    You don't need to run kitchen init; the berks cookbook command handles those tasks.

  3. Run kitchen converge. The newly created cookbook doesn't do anything interesting at this point, but it does converge.

Note

You can also use berks init to initialize an existing cookbook to use Berkshelf.

To use Berkshelf to manage a cookbook's external dependencies, the cookbook's root directory must contain a Berksfile, which is a configuration file that specifies how Berkshelf should manage dependencies. When you used berks cookbook to create the external_cookbook cookbook, it created a Berksfile with the following contents.

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source "https://supermarket.chef.io" metadata

This file has the following declarations:

  • source – The URL of a cookbook source.

    A Berksfile can have any number of source declarations, each of which specifies a default source for dependent cookbooks. If you do not explicitly specify a cookbook's source, Berkshelf looks in the default repositories for a cookbook with the same name. The default Berksfile includes a single source attribute which specifies the community cookbook repository. That repository contains the getting-started cookbook, so you can leave the line unchanged.

  • metadata – Directs Berkshelf to include cookbook dependencies that are declared in the cookbook's metadata.rb file.

    You can also declare a dependent cookbook in the Berksfile by including a cookbook attribute, as discussed later.

There are two ways to declare a cookbook dependency:

  • By including a cookbook declaration in the Berksfile.

    This is the approach used by AWS OpsWorks Stacks. For example to specify the getting-started cookbook used in this example, include cookbook "getting-started" in the Berksfile. Berkshelf will then look in the default repositories for a cookbook with that name. You can also use cookbook to explicitly specify a cookbook source, and even a particular version. For more information, see Berkshelf.

  • By including a metadata declaration in the Berksfile and declaring the dependency in metadata.rb.

    This declaration directs Berkshelf to include cookbook dependencies that are declared in metadata.rb. For example, to declare a getting-started dependency, add a depends 'getting-started' declaration to the cookbook's metadata.rb file.

This example uses the first approach, for consistency with AWS OpsWorks Stacks.

To install the getting-started cookbook

  1. Edit the default Berksfile to replace the metadata declaration with a cookbook declaration for getting-started. The contents should look like the following.

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    source "https://supermarket.chef.io" cookbook 'getting-started'
  2. Run berks install, which downloads the getting-started cookbook from the community cookbook repository to your workstation's Berkshelf directory, which is typically ~/.berkshelf. This directory is often simply called the Berkshelf. Look in the Berkshelf's cookbooks directory, and you should see the directory for the getting-started cookbook, which will be named something like getting-started-0.4.0.

  3. Replace external_cookbook::default in the .kitchen.yml run list with getting-started::default. This example doesn't run any recipes from external_cookbook; it's basically just a way to use the getting-started cookbook. The .kitchen.yml file should now look like the following.

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    --- driver: name: vagrant provisioner: name: chef_solo platforms: - name: ubuntu-12.04 suites: - name: default run_list: - recipe[getting-started::default] attributes:
  4. Run kitchen converge and then use kitchen login to log in to the instance. The login directory should contain a file named chef-getting-started.txt with something like the following:

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    Welcome to Chef! This is Chef version 11.12.8. Running on ubuntu. Version 12.04.

    Test Kitchen installs cookbooks in the instance's /tmp/kitchen/cookbooks directory. If you list the contents of that directory, you will see two cookbooks: external_cookbook and getting-started.

  5. Run kitchen destroy to shut down the instance. The next example uses an AWS OpsWorks Stacks instance.

Using Berkshelf with AWS OpsWorks Stacks

AWS OpsWorks Stacks optionally supports Berkshelf for Chef 11.10 stacks. To use Berkshelf with your stack, you must do the following.

  • Enable Berkshelf for the stack.

    AWS OpsWorks Stacks then handles the details of installing Berkshelf on the stack's instances.

  • Add a Berksfile to your cookbook repository's root directory.

    The Berksfile should contain source and cookbook declarations for all dependent cookbooks.

When AWS OpsWorks Stacks installs your custom cookbook repository on an instance, it uses Berkshelf to install the dependent cookbooks that are declared in the repository's Berksfile. For more information, see Using Berkshelf.

This example shows how to use Berkshelf to install the getting-started community cookbook on an AWS OpsWorks Stacks instance. It also installs a version of the createfile custom cookbook, which creates a file in a specified directory. For more information on how createfile works, see Installing a File from a Cookbook.

Note

If this is the first time you have installed a custom cookbook on an AWS OpsWorks Stacks stack, you should first go through the Running a Recipe on a Linux Instance example.

Start by creating a stack, as summarized in the following. For more information, see Create a New Stack.

Create a stack

  1. Open the AWS OpsWorks Stacks console and click Add Stack.

  2. Specify the following settings, accept the defaults for the other settings, and click Add Stack.

    • Name – BerksTest

    • Default SSH key – An Amazon EC2 key pair

    If you need to create an Amazon EC2 key pair, see Amazon EC2 Key Pairs. Note that the key pair must belong to the same AWS region as the instance. The example uses the default US West (Oregon) region.

  3. Click Add a layer and add a custom layer to the stack with the following settings.

    • Name – BerksTest

    • Short name – berkstest

    You could actually use any layer type for this example. However, the example doesn't require any of the packages that are installed by the other layers, so a custom layer is the simplest approach.

  4. Add a 24/7 instance to the BerksTest layer with default settings, but don't start it yet.

With AWS OpsWorks Stacks, cookbooks must be in a remote repository with a standard directory structure. You then provide the download information to AWS OpsWorks Stacks, which automatically downloads the repository to each of the stack's instances on startup. For simplicity, the repository for this example is a public Amazon S3 archive, but AWS OpsWorks Stacks also supports HTTP archives, Git repositories, and Subversion repositories. For more information, see Cookbook Repositories.

To create the cookbook repository

  1. In your opsworks_cookbooks directory, create a directory named berkstest_cookbooks. If you prefer, you can create this directory anywhere that you find convenient, because you will upload it to a repository.

  2. Add a file named Berksfile to berkstest_cookbooks with the following contents.

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    source "https://supermarket.chef.io" cookbook 'getting-started'

    This file declares the getting-started cookbook dependency, and directs Berkshelf to download it from the community cookbook site.

  3. Add a createfile directory to berkstest_cookbooks that contains the following.

    • A metadata.rb file with the following contents.

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      name "createfile" version "0.1.0"
    • A files/default directory that contains an example_data.json file with the following content.

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      { "my_name" : "myname", "your_name" : "yourname", "a_number" : 42, "a_boolean" : true }

      The file's name and content are arbitrary. The recipe simply copies the file to the specified location.

    • A recipes directory that contains a default.rb file with the following recipe code.

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      directory "/srv/www/shared" do mode 0755 owner 'root' group 'root' recursive true action :create end cookbook_file "/srv/www/shared/example_data.json" do source "example_data.json" mode 0644 action :create_if_missing end

      This recipe creates /srv/www/shared and copies example_data.json to that directory from the cookbook's files directory.

  4. Create a .zip archive of berkstest_cookbooks, Upload the archive to an Amazon S3 bucket, make the archive public, and record the archive's URL. It should look something like https://s3.amazonaws.com/cookbook_bucket/berkstest_cookbooks.zip.

You can now install the cookbooks and run the recipe.

To install the cookbooks and run the recipes

  1. Edit the stack to enable custom cookbooks, and specify the following settings.

    • Repository typeHttp Archive

    • Repository URL – The cookbook archive URL that you recorded earlier

    • Manage BerkshelfYes

    The first two settings provide AWS OpsWorks Stacks with the information it needs to download the cookbook repository to your instances. The last setting enables Berkshelf support, which downloads the getting-started cookbook to the instance. Accept the default values for the other settings and click Save to update the stack configuration.

  2. Edit the BerksTest layer to add the following recipes to the layer's Setup lifecycle event.

    • getting-started::default

    • createfile::default

  3. Start the instance. The Setup event occurs after the instance finishes booting. AWS OpsWorks Stacks then installs the cookbook repository, uses Berkshelf to download the getting-started cookbook, and runs the layer's setup and deploy recipes, including getting-started::default and createfile::default.

  4. After the instance is online, use SSH to log in. You should see the following

    • /srv/www/shared should contain example_data.json.

    • /root should contain chef-getting-started.txt.

      AWS OpsWorks Stacks runs recipes as root, so getting-started installs the file in the /root directory rather than your home directory.