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user resource

Resources Reference page


Use the user resource to add users, update existing users, remove users, and to lock/unlock user passwords.

Note

System attributes are collected by Ohai at the start of every Chef Infra Client run. By design, the actions available to the user resource are processed after the start of a Chef Infra Client run. This means that system attributes added or modified by the user resource during a Chef Infra Client run must be reloaded before they can be available to Chef Infra Client. These system attributes can be reloaded in two ways: by picking up the values at the start of the (next) Chef Infra Client run or by using the ohai resource to reload the system attributes during the current Chef Infra Client run.

Syntax


A user resource block manages users on a node:

user 'a user' do
  comment 'A random user'
  uid 1234
  gid 'groupname'
  home '/home/random'
  shell '/bin/bash'
  password '$1$JJsvHslasdfjVEroftprNn4JHtDi'
end

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

user 'name' do
  comment                    String
  force                      true, false # see description
  gid                        String, Integer
  home                       String
  iterations                 Integer
  manage_home                true, false
  non_unique                 true, false
  password                   String
  salt                       String
  shell                      String
  system                     true, false
  uid                        String, Integer
  username                   String # defaults to 'name' if not specified
  action                     Symbol # defaults to :create if not specified
end

where:

  • user is the resource
  • name is the name of the resource block
  • action identifies the steps Chef Infra Client will take to bring the node into the desired state
  • comment, force, gid, home, iterations, manage_home, non_unique, password, salt, shell, system, uid, and username are properties of this resource, with the Ruby type shown. See “Properties” section below for more information about all of the properties that may be used with this resource.

Actions


The user resource has the following actions:

:create
Default. Create a user with given properties. If a user already exists (but does not match), update that user to match.
:lock
Lock a user’s password.
:manage
Manage an existing user. This action does nothing if the user does not exist.
:modify
Modify an existing user. This action raises an exception if the user 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 a Chef Infra Client run.
:remove
Remove a user.
:unlock
Unlock a user’s password.

Properties


The user resource has the following properties:

comment
Ruby Type: String

One (or more) comments about the user.

force
Ruby Type: true, false

Force the removal of a user. May be used only with the :remove action.

Warning

Using this property may leave the system in an inconsistent state. For example, a user account will be removed even if the user is logged in. A user’s home directory will be removed, even if that directory is shared by multiple users.

gid
Ruby Type: String, Integer

The identifier for the group. This property was previously named group and both continue to function.

home
Ruby Type: String

The location of the home directory.

iterations
Ruby Type: Integer

macOS platform only. The number of iterations for a password with a SALTED-SHA512-PBKDF2 shadow hash.

manage_home
Ruby Type: true, false

Manage a user’s home directory.

When used with the :create action, a user’s home directory is created based on HOME_DIR. If the home directory is missing, it is created unless CREATE_HOME in /etc/login.defs is set to no. When created, a skeleton set of files and subdirectories are included within the home directory.

When used with the :modify action, a user’s home directory is moved to HOME_DIR. If the home directory is missing, it is created unless CREATE_HOME in /etc/login.defs is set to no. The contents of the user’s home directory are moved to the new location.

non_unique
Ruby Type: true, false

Create a duplicate (non-unique) user account.

password
Ruby Type: String

The password shadow hash

salt
Ruby Type: String

A SALTED-SHA512-PBKDF2 hash.

shell
Ruby Type: String

The login shell.

system
Ruby Type: true, false

Create a system user. This property may be used with useradd as the provider to create a system user which passes the -r flag to useradd.

uid
Ruby Type: String, Integer

The numeric user identifier.

username
Ruby Type: String

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


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 user resource in recipes:

Create a system user

user 'systemguy' do
  comment 'system guy'
  system true
  shell '/bin/false'
end

Create a system user with a variable

The following example shows how to create a system user. In this instance, the home value is calculated and stored in a variable called user_home which sets the user’s home attribute.

user_home = "/home/#{node['cookbook_name']['user']}"

user node['cookbook_name']['user'] do
  gid node['cookbook_name']['group']
  shell '/bin/bash'
  home user_home
  system true
  action :create
end

Use SALTED-SHA512-PBKDF2 passwords

macOS 10.8 (and higher) calculates the password shadow hash using SALTED-SHA512-PBKDF2. The length of the shadow hash value is 128 bytes, the salt value is 32 bytes, and an integer specifies the number of iterations. The following code will calculate password shadow hashes for macOS 10.8 (and higher):

password = 'my_awesome_password'
salt = OpenSSL::Random.random_bytes(32)
iterations = 25000 # Any value above 20k should be fine.

shadow_hash = OpenSSL::PKCS5::pbkdf2_hmac(
  password,
  salt,
  iterations,
  128,
  OpenSSL::Digest::SHA512.new
).unpack('H*').first
salt_value = salt.unpack('H*').first

Use the calculated password shadow hash with the user resource:

user 'my_awesome_user' do
  password 'cbd1a....fc843'  # Length: 256
  salt 'bd1a....fc83'        # Length: 64
  iterations 25000
end