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metadata.rb

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Every cookbook requires a small amount of metadata. A file named metadata.rb is located at the top of every cookbook directory structure. The contents of the metadata.rb file provides information that helps Chef Infra Client and Server correctly deploy cookbooks to each node.

A metadata.rb file is:

  • Located at the top level of a cookbook’s directory structure.
  • Compiled whenever a cookbook is uploaded to the Chef Infra Server or when the knife cookbook metadata subcommand is run, and then stored as JSON data.
  • Created automatically by knife whenever the knife cookbook create subcommand is run.
  • Edited using a text editor, and then re-uploaded to the Chef Infra Server as part of a cookbook upload.

Error Messages

The Chef Infra Server will only try to distribute the cookbooks that are needed to configure an individual node. This is determined by identifying the roles and recipes that are assigned directly to that system, and then to expand the list of dependencies, and then to deliver that entire set to the node. In some cases, if the dependency is not specified in the cookbook’s metadata, the Chef Infra Server may not treat that dependency as a requirement, which will result in an error message. If an error message is received from the Chef Infra Server about cookbook distribution, verify the depends entries in the metadata.rb file, and then try again.

Note

A metadata.json file can be edited directly, should temporary changes be required. Any subsequent upload or action that generates metadata will cause the existing metadata.json file to be overwritten with the newly generated metadata. Therefore, any permanent changes to cookbook metadata should be done in the metadata.rb file, and then re-uploaded to the Chef Infra Server.

Version Constraints

Many fields in a cookbook’s metadata allow the user to constrain versions. There are a set of operators common to all fields:

SpecificationOperator
Pessimistic (see note below)~>
Equal to=
Greater than or equal to>=
Greater than>
Less than<
Less than or equal to<=

Note

Pessimistic locking is enabled by proper semantic versioning of cookbooks. If we’re on version 2.2.3 of a cookbook, we know that the API will be stable until the 3.0.0 release. Using traditional operators, we’d write this as >= 2.2.0, < 3.0. Instead, we can write this by combining a tilde “~” and right angle bracket “>"–often called a tilde-rocket or “twiddle-wakka”–followed by the major and minor version numbers. For example: ~> 2.2

Settings

This configuration file has the following settings:

chef_version

A range of Chef Client versions that are supported by this cookbook. All version constraint operators are applicable to this field.

For example, to match any 14.x version of the Chef Client, but not 13.x or 15.x:

chef_version '~> 14.0'

A more complex example where you set both a lower and upper bound of the Chef Infra Client version:

chef_version '>= 14.2.1', '< 14.5.1'
depends

This field requires that a cookbook with a matching name and version exists on the Chef Infra Server. When the match exists, the Chef Infra Server includes the dependency as part of the set of cookbooks that are sent to the node during a Chef Infra Client run. It is very important that the depends field contain accurate data. If a dependency statement is inaccurate, Chef Infra Client may not be able to complete the configuration of the system. All version constraint operators are applicable to this field.

For example, to set a dependency a cookbook named cats:

depends 'cats'

or, to set a dependency on the same cookbook, but only when the version is less than 1.0:

depends 'cats', '< 1.0'
description

A short description of a cookbook and its functionality.

For example:

description 'A fancy cookbook that manages a herd of cats!'
gem

Specifies a gem dependency for installation in Chef Infra Client through bundler. The gem installation occurs after all cookbooks are synchronized but before loading any other cookbooks. Use this attribute one time for each gem dependency. For example:

gem 'loofah'
gem 'chef-sugar'

Warning

Use the gem setting only for making external chef libraries shipped as gems accessible in a Chef Infra Client run for libraries and attribute files. The gem setting in metadata.rb allows for the early installation of this specific type of gem, with the fundamental limitation that it cannot install native gems. Do not install native gems with the gem setting in metadata.rb . The gem setting is not a general purpose replacement for the chef_gem resource, and does not internally re-use the chef_gem resource. Native gems require C compilation and must not be installed with metadata.rb because metadata.rb runs before any recipe code runs. Consequently, Chef Infra Client cannot install the C compilers before the gem installation occurs. Instead, install native gems with the chef_gem resource called from the recipe code. You’ll also need to use the build_essential resource in the recipe code to install the prerequisite compilers onto the system. Pure ruby gems can also be installed with metadata.rb.
issues_url

The URL for the location in which a cookbook’s issue tracking is maintained. This setting is also used by Chef Supermarket. In Chef Supermarket, this value is used to define the destination for the “View Issues” link.

For example:

issues_url 'https://github.com/chef-cookbooks/chef-client/issues'
license

The type of license under which a cookbook is distributed: Apache v2.0, GPL v2, GPL v3, MIT, or license 'Proprietary - All Rights Reserved (default). Please be aware of the licenses for files inside of a cookbook and be sure to follow any restrictions they describe.

For example:

license 'Apache-2.0'

or:

license 'GPL-3.0'

or:

license 'MIT'

or:

license 'Proprietary - All Rights Reserved'
maintainer

The name of the person responsible for maintaining a cookbook, either an individual or an organization.

For example:

maintainer 'Adam Jacob'
maintainer_email

The email address for the person responsible for maintaining a cookbook. Only one email can be listed here, so if this needs to be forwarded to multiple people consider using an email address that is already setup for mail forwarding.

For example:

maintainer_email 'adam@example.com'
name

Required. The name of the cookbook.

For example:

name 'cats'
ohai_version

A range of Ohai versions that are supported by this cookbook. All version constraint operators are applicable to this field.

For example, to match any 8.x version of Ohai, but not 7.x or 9.x:

ohai_version '~> 8'

Note

This setting is not visible in Chef Supermarket.
privacy

Specify a cookbook as private.

For example:

privacy true
source_url

The URL for the location in which a cookbook’s source code is maintained. This setting is also used by Chef Supermarket. In Chef Supermarket, this value is used to define the destination for the “View Source” link.

For example:

source_url 'https://github.com/chef-cookbooks/chef-client'
supports

Show that a cookbook has a supported platform. Use a version constraint to define dependencies for platform versions: < (less than), <= (less than or equal to), = (equal to), >= (greater than or equal to), ~> (approximately greater than), or > (greater than). To specify more than one platform, use more than one supports field, once for each platform.

For example, to support every version of Ubuntu:

supports 'ubuntu'

or, to support versions of Ubuntu greater than or equal to 16.04:

supports 'ubuntu', '>= 16.04'

or, to support only Ubuntu 18.04:

supports 'ubuntu', '= 18.04'

Here is a list of all of the supported specific operating systems:

%w( aix amazon centos fedora freebsd debian oracle mac_os_x redhat suse opensuseleap ubuntu windows zlinux ).each do |os|
  supports os
end
version

The current version of a cookbook. Version numbers always follow a simple three-number version sequence.

For example:

version '2.0.0'

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