ssh_known_hosts_entry Resource

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Use the ssh_known_hosts_entry resource to add an entry for the specified host in /etc/ssh/ssh_known_hosts or a user’s known hosts file if specified.

New in Chef Infra Client 14.3.

Syntax

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

ssh_known_hosts_entry 'name' do
  file_location      String # default value: "/etc/ssh/ssh_known_hosts"
  group              String, Integer # default value: The root user's group depending on platform.
  hash_entries       true, false # default value: false
  host               String # default value: 'name' unless specified
  key                String
  key_type           String # default value: "rsa"
  mode               String # default value: "0644"
  owner              String, Integer # default value: "root"
  port               Integer # default value: 22
  timeout            Integer # default value: 30
  action             Symbol # defaults to :create if not specified
end

where:

• ssh_known_hosts_entry 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.
• file_location, group, hash_entries, host, key, key_type, mode, owner, port, and timeout are the properties available to this resource.

Actions

The ssh_known_hosts_entry resource has the following actions:

:create

Create an entry in the ssh_known_hosts file. (default)

:flush

Immediately flush the entries to the config file. Without this the actual writing of the file is delayed in the Chef Infra Client run so all entries can be accumulated before writing the file out.

: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.

Properties

The ssh_known_hosts_entry resource has the following properties:

file_location

Ruby Type: String | Default Value: /etc/ssh/ssh_known_hosts

The location of the ssh known hosts file. Change this to set a known host file for a particular user.

group

Ruby Type: String, Integer | Default Value: The root user's group depending on platform.

The file group for the ssh_known_hosts file.

hash_entries

Ruby Type: true, false | Default Value: false

Hash the hostname and addresses in the ssh_known_hosts file for privacy.

host

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

The host to add to the known hosts file.

key

Ruby Type: String

An optional key for the host. If not provided this will be automatically determined.

key_type

Ruby Type: String | Default Value: rsa

The type of key to store.

mode

Ruby Type: String | Default Value: 0644

The file mode for the ssh_known_hosts file.

owner

Ruby Type: String, Integer | Default Value: root

The file owner for the ssh_known_hosts file.

port

Ruby Type: Integer | Default Value: 22

The server port that the ssh-keyscan command will use to gather the public key.

timeout

Ruby Type: Integer | Default Value: 30

The timeout in seconds for ssh-keyscan.

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 delay in seconds between retry attempts.

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.

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, for each 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, for each 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 ssh_known_hosts_entry resource in recipes:

Add a single entry for github.com with the key auto detected

ssh_known_hosts_entry 'github.com'

Add a single entry with your own provided key

ssh_known_hosts_entry 'github.com' do
  key 'node.example.com ssh-rsa ...'
end