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kernel_module resource

Resources Reference page


Use the kernel_module resource to manage kernel modules on Linux systems. This resource can load, unload, blacklist, disable, install, and uninstall modules.

New in Chef Infra Client 14.3.

Syntax


The kernel_module resource has the following syntax:

kernel_module 'name' do
  load_dir        String # default value: "/etc/modules-load.d"
  modname         String # default value: 'name' unless specified
  options         Array
  unload_dir      String # default value: "/etc/modprobe.d"
  action          Symbol # defaults to :install if not specified
end

where:

  • kernel_module 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.
  • load_dir, modname, options, and unload_dir are the properties available to this resource.

Actions


The kernel_module resource has the following actions:

:blacklist
Blacklist a kernel module.
:disable

Disable a kernel module

New in Chef Client 15.2.

:install
Default. Load kernel module, and ensure it loads on reboot.
:load
Load a kernel module.
: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.
:uninstall
Unload a kernel module and remove module config, so it doesn’t load on reboot.
:unload
Unload kernel module.

Properties


The kernel_module resource has the following properties:

load_dir
Ruby Type: String | Default Value: "/etc/modules-load.d"

The directory to load modules from.

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

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

options
Ruby Type: Array

An optional property to set options for the kernel module.

New in Chef Infra Client 15.4

unload_dir
Ruby Type: String | Default Value: "/etc/modprobe.d"

The modprobe.d directory.


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 Chef Infra 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 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.

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.

Properties

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 kernel_module resource in recipes:

Install and load a kernel module and ensure it loads on reboot.

kernel_module 'loop'

Install and load a kernel with a specific set of options and ensure it loads on reboot.

Consult kernel module documentation for specific options that are supported.

kernel_module 'loop' do
  options [ 'max_loop=4', 'max_part=8' ]
end

Load a kernel module.

kernel_module 'loop' do
  action :load
end

Unload a kernel module and remove module config so it doesn’t load on reboot.

kernel_module 'loop' do
  action :uninstall
end

Unload kernel module.

kernel_module 'loop' do
  action :unload
end

Blacklist a module from loading.

kernel_module 'loop' do
  action :blacklist
end

Disable a kernel module.

kernel_module 'loop' do
  action :disable
end