hostname Resource

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Use the hostname resource to set the system’s hostname, configure hostname and hosts config file, and re-run the Ohai hostname plugin so the hostname will be available in subsequent cookbooks.

New in Chef Infra Client 14.0.

Syntax

The full syntax for all of the properties that are available to the hostname resource is:

hostname 'name' do
  aliases             Array
  compile_time        true, false # default value: true
  fqdn                String
  hostname            String # default value: 'name' unless specified
  ipaddress           String # default value: The node's IP address as determined by Ohai.
  windows_reboot      true, false # default value: true
  action              Symbol # defaults to :set if not specified
end

where:

• hostname is the resource.
• name is the name given to the resource block.
• action identifies which steps Chef Infra Client will take to bring the node into the desired state.
• aliases, compile_time, fqdn, hostname, ipaddress, and windows_reboot are the properties available to this resource.

Actions

The hostname resource has the following actions:

: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 a Chef Infra Client run.

:set

Sets the node’s hostname (default)

Properties

The hostname resource has the following properties:

aliases

Ruby Type: Array

An array of hostname aliases to use when configuring the hosts file.

compile_time

Ruby Type: true, false | Default Value: true

Determines whether or not the resource should be run at compile time.

fqdn

Ruby Type: String

An optional property to set the fqdn if it differs from the resource block’s hostname.

New in Chef Infra Client 17.0

hostname

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

An optional property to set the hostname if it differs from the resource block’s name.

ipaddress

Ruby Type: String | Default Value: The node's IP address as determined by Ohai.

The IP address to use when configuring the hosts file.

windows_reboot

Ruby Type: true, false | Default Value: true

Determines whether or not Windows should be reboot after changing the hostname, as this is required for the change to take effect.

Common Resource Functionality

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

Common Properties

The following properties are common to every resource:

compile_time

Ruby Type: true, false | Default Value: false

Control the phase during which the resource is run on the node. Set to true to run while the resource collection is being built (the compile phase). Set to false to run while Chef Infra Client is configuring the node (the converge phase).

ignore_failure

Ruby Type: true, false, :quiet | Default Value: false

Continue running a recipe if a resource fails for any reason. :quiet will not display the full stack trace and the recipe will continue to run if a resource fails.

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 Chef InfraClient.

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.

If the referenced resource does not exist, an error is raised. In contrast, subscribes will not fail if the source resource is not found.

A timer specifies the point during a Chef Infra 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 a Chef Infra 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.

If the other resource does not exist, the subscription will not raise an error. Contrast this with the stricter semantics of notifies, which will raise an error if the other resource does not exist.

A timer specifies the point during a Chef Infra 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 a Chef Infra 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 a Chef Infra Client run. Based on the results of this evaluation, a guard property is then used to tell Chef Infra 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 Chef Infra Client to do nothing.

The following properties can be used to define a guard that is evaluated during the execution phase of a Chef Infra 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 the hostname resource in recipes:

Set the hostname using the IP address, as detected by Ohai:

hostname 'example'

Manually specify the hostname and IP address:

hostname 'statically_configured_host' do
  hostname 'example'
  ipaddress '198.51.100.2'
end