systemd_unit Resource

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Use the systemd_unit resource to create, manage, and run systemd units.

New in Chef Infra Client 12.11.

Syntax

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

systemd_unit 'name' do
  content              String, Hash
  triggers_reload      true, false # default value: true
  unit_name            String # default value: 'name' unless specified
  user                 String
  verify               true, false # default value: true
  action               Symbol # defaults to :nothing if not specified
end

where:

• systemd_unit 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.
• content, triggers_reload, unit_name, user, and verify are the properties available to this resource.

Actions

The systemd_unit resource has the following actions:

:create

Create a unit file, if it does not already exist.

:delete

Delete a unit file, if it exists.

:disable

Ensure the unit will not be started after the next system boot.

:enable

Ensure the unit will be started after the next system boot.

:mask

Ensure the unit will not start, even to satisfy dependencies.

:nothing

Default. Do nothing with the unit.

:preset

Restore the preset “enable/disable” configuration for a unit. New in Chef Client 14.0.

:reenable

Reenable a unit file. New in Chef Client 14.0.

:reload

Reload the configuration file for a unit.

:reload_or_restart

For units that are services, this action reloads the configuration of the service without restarting, if possible; otherwise, it will restart the service so the new configuration is applied.

:reload_or_try_restart

For units that are services, this action reloads the configuration of the service without restarting, if possible; otherwise, it will try to restart the service so the new configuration is applied.

:restart

Restart a unit.

:revert

Revet to a vendor’s version of a unit file. New in Chef Client 14.0.

:start

Start a unit based in its systemd unit file.

:stop

Stop a running unit.

:try_restart

Try to restart a unit if the unit is running.

:unmask

Stop the unit from being masked and cause it to start as specified.

Properties

The systemd_unit resource has the following properties:

content

Ruby Type: String, Hash

A string or hash that contains a systemd unit file definition that describes the properties of systemd-managed entities, such as services, sockets, devices, and so on. In Chef Infra Client 14.4 or later, repeatable options can be implemented with an array.

triggers_reload

Ruby Type: true, false | Default Value: true

Specifies whether to trigger a daemon reload when creating or deleting a unit.

unit_name

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

The name of the unit file if it differs from the resource block’s name.

New in Chef Client 13.7

user

Ruby Type: String

The user account that the systemd unit process is run under. The path to the unit for that user would be something like ‘/etc/systemd/user/sshd.service’. If no user account is specified, the systemd unit will run under a ‘system’ account, with the path to the unit being something like ‘/etc/systemd/system/sshd.service’.

verify

Ruby Type: true, false | Default Value: true

Specifies if the unit will be verified before installation. Systemd can be overly strict when verifying units, so in certain cases it is preferable not to verify the unit.

Unit file verification

The unit file is verified via a systemd-analyze verify call before being written to disk.

Be aware that the referenced commands and files need to already exist before verification.

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 systemd_unit resource in recipes:

Create systemd service unit file from a Hash

systemd_unit 'etcd.service' do
  content({Unit: {
            Description: 'Etcd',
            Documentation: ['https://coreos.com/etcd', 'man:etcd(1)'],
            After: 'network.target',
          },
          Service: {
            Type: 'notify',
            ExecStart: '/usr/local/etcd',
            Restart: 'always',
          },
          Install: {
            WantedBy: 'multi-user.target',
          }})
  action [:create, :enable]
end

Create systemd service unit file from a String

systemd_unit 'sysstat-collect.timer' do
  content <<~EOU
  [Unit]
  Description=Run system activity accounting tool every 10 minutes

  [Timer]
  OnCalendar=*:00/10

  [Install]
  WantedBy=sysstat.service
  EOU

  action [:create, :enable]
end