group resource

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Use the group resource to manage a local group.

Syntax

The group resource has the following syntax:

group 'name' do
  append                true, false # default value: false
  excluded_members      String, Array
  gid                   String, Integer
  group_name            String # default value: 'name' unless specified
  members               String, Array
  non_unique            true, false # default value: false
  system                true, false # default value: false
  action                Symbol # defaults to :create if not specified
end

where:

  • group is the resource.
  • name is the name given to the resource block.
  • action identifies which steps the chef-client will take to bring the node into the desired state.
  • append, excluded_members, gid, group_name, members, non_unique, and system are the properties available to this resource.

Actions

The group resource has the following actions:

:create
Default. Create a group. If a group already exists (but does not match), update that group to match.
:manage
Manage an existing group. This action does nothing if the group does not exist.
:modify
Modify an existing group. This action raises an exception if the group does not exist.
:nothing
This resource block does not act unless notified by another resource to take action. Once notified, this resource block either runs immediately or is queued up to run at the end of the Chef Client run.
:remove
Remove a group.

Properties

The group resource has the following properties:

append

Ruby Type: true, false | Default Value: false

How members should be appended and/or removed from a group. When true, members are appended and excluded_members are removed. When false, group members are reset to the value of the members property.

excluded_members

Ruby Type: String, Array

Remove users from a group. May only be used when append is set to true.

gid

Ruby Type: String, Integer

The identifier for the group.

group_name

Ruby Type: String | Default Value: The resource block's name

The name of the group. Default value: the name of the resource block. See “Syntax” section above for more information.

members

Ruby Type: Array

Which users should be set or appended to a group. When more than one group member is identified, the list of members should be an array: members ['user1', 'user2'].

non_unique

Ruby Type: true, false | Default Value: false

Allow gid duplication. May only be used with the Groupadd provider.

system

Ruby Type: true, false | Default Value: false

Set if a group belongs to a system group. Set to true if the group belongs to a system group.

Common Resource Functionality

Chef resources include common properties, notifications, and resource guards.

Common Properties

The following properties are common to every resource:

ignore_failure

Ruby Type: true, false | Default Value: false

Continue running a recipe if a resource fails for any reason.

retries

Ruby Type: Integer | Default Value: 0

The number of attempts to catch exceptions and retry the resource.

retry_delay

Ruby Type: Integer | Default Value: 2

The retry delay (in seconds).

sensitive

Ruby Type: true, false | Default Value: false

Ensure that sensitive resource data is not logged by the chef-client.

Notifications

notifies

Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may notify another resource to take action when its state changes. Specify a 'resource[name]', the :action that resource should take, and then the :timer for that action. A resource may notify more than one resource; use a notifies statement for each resource to be notified.

A timer specifies the point during the Chef Client run at which a notification is run. The following timers are available:

:before
Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
Default. Specifies that a notification should be queued up, and then executed at the end of the Chef Client run.
:immediate, :immediately
Specifies that a notification should be run immediately, per resource notified.

The syntax for notifies is:

notifies :action, 'resource[name]', :timer
subscribes
Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may listen to another resource, and then take action if the state of the resource being listened to changes. Specify a 'resource[name]', the :action to be taken, and then the :timer for that action.

Note that subscribes does not apply the specified action to the resource that it listens to - for example:

file '/etc/nginx/ssl/example.crt' do
  mode '0600'
  owner 'root'
end

service 'nginx' do
  subscribes :reload, 'file[/etc/nginx/ssl/example.crt]', :immediately
end

In this case the subscribes property reloads the nginx service whenever its certificate file, located under /etc/nginx/ssl/example.crt, is updated. subscribes does not make any changes to the certificate file itself, it merely listens for a change to the file, and executes the :reload action for its resource (in this example nginx) when a change is detected.

A timer specifies the point during the Chef Client run at which a notification is run. The following timers are available:

:before
Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
Default. Specifies that a notification should be queued up, and then executed at the end of the Chef Client run.
:immediate, :immediately
Specifies that a notification should be run immediately, per resource notified.

The syntax for subscribes is:

subscribes :action, 'resource[name]', :timer

Guards

A guard property can be used to evaluate the state of a node during the execution phase of the chef-client run. Based on the results of this evaluation, a guard property is then used to tell the chef-client if it should continue executing a resource. A guard property accepts either a string value or a Ruby block value:

  • A string is executed as a shell command. If the command returns 0, the guard is applied. If the command returns any other value, then the guard property is not applied. String guards in a powershell_script run Windows PowerShell commands and may return true in addition to 0.
  • A block is executed as Ruby code that must return either true or false. If the block returns true, the guard property is applied. If the block returns false, the guard property is not applied.

A guard property is useful for ensuring that a resource is idempotent by allowing that resource to test for the desired state as it is being executed, and then if the desired state is present, for the chef-client to do nothing.

The following properties can be used to define a guard that is evaluated during the execution phase of the chef-client run:

not_if
Prevent a resource from executing when the condition returns true.
only_if
Allow a resource to execute only if the condition returns true.

Examples

The following examples demonstrate various approaches for using resources in recipes:

Append users to groups

group 'www-data' do
  action :modify
  members 'maintenance'
  append true
end

Add a user to group on the Windows platform

group 'Administrators' do
  members ['domain\foo']
  append true
  action :modify
end