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script resource

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Resources Reference page

Use the script resource to execute scripts using a specified interpreter, such as Bash, csh, Perl, Python, or Ruby. This resource may also use any of the actions and properties that are available to the execute resource. Commands that are executed with this resource are (by their nature) not idempotent, as they are typically unique to the environment in which they are run. Use not_if and only_if to guard this resource for idempotence.

This resource is the base resource for several other resources used for scripting on specific platforms. For more information about specific resources for specific platforms, see the following topics:

Changed in 12.19 to support windows alternate user identity in execute resources

Syntax

A script resource block typically executes scripts using a specified interpreter, such as Bash, csh, Perl, Python, or Ruby:

script 'extract_module' do
  interpreter "bash"
  cwd ::File.dirname(src_filepath)
  code <<-EOH
    mkdir -p #{extract_path}
    tar xzf #{src_filename} -C #{extract_path}
    mv #{extract_path}/*/* #{extract_path}/
  EOH
  not_if { ::File.exist?(extract_path) }
end

where:

  • interpreter specifies the command shell to use
  • cwd specifies the directory from which the command is run

  • code specifies the command to run

    It is more common to use the script-based resource that is specific to the command shell. Chef has shell-specific resources for Bash, csh, ksh, Perl, Python, and Ruby.

    The same command as above, but run using the bash resource:

    bash 'extract_module' do
  cwd ::File.dirname(src_filepath)
  code <<-EOH
    mkdir -p #{extract_path}
    tar xzf #{src_filename} -C #{extract_path}
    mv #{extract_path}/*/* #{extract_path}/
  EOH
  not_if { ::File.exist?(extract_path) }
end

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

script 'name' do
  code                       String
  creates                    String
  cwd                        String
  environment                Hash
  flags                      String
  group                      String, Integer
  interpreter                String
  path                       Array
  returns                    Integer, Array
  timeout                    Integer, Float
  user                       String
  password                   String
  domain                     String
  umask                      String, Integer
  action                     Symbol # defaults to :run if not specified
end

where:

  • script is the resource
  • name is the name of the resource block
  • cwd is the location from which the command is run
  • action identifies the steps Chef Infra Client will take to bring the node into the desired state
  • code, creates, cwd, environment, flags, group, interpreter, path, returns, timeout, user, password, domain and umask 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 script resource has the following actions:

:nothing
Prevent a command from running. This action is used to specify that a command is run only when another resource notifies it.
:run
Default. Run a script.

Properties

The script resource has the following properties:

code
Ruby Type: String

A quoted (" “) string of code to be executed.

creates
Ruby Type: String

Prevent a command from creating a file when that file already exists.

cwd
Ruby Type: String

The current working directory from which the command will be run.

environment
Ruby Type: Hash

A Hash of environment variables in the form of ({"ENV_VARIABLE" => "VALUE"}). (These variables must exist for a command to be run successfully.)

flags
Ruby Type: String

One or more command line flags that are passed to the interpreter when a command is invoked.

group
Ruby Type: String, Integer

The group name or group ID that must be changed before running a command.

interpreter
Ruby Type: String

The script interpreter to use during code execution.

returns
Ruby Type: Integer, Array | Default Value: 0

The return value for a command. This may be an array of accepted values. An exception is raised when the return value(s) do not match.

timeout
Ruby Type: Integer, Float | Default Value: 3600

The amount of time (in seconds) a command is to wait before timing out.

user
Ruby Type: String

The user name of the user identity with which to launch the new process. Default value: nil. The user name may optionally be specified with a domain, i.e. domainuser or user@my.dns.domain.com via Universal Principal Name (UPN)format. It can also be specified without a domain simply as user if the domain is instead specified using the domain attribute. On Windows only, if this property is specified, the password property must be specified.

password
Ruby Type: String

Windows only: The password of the user specified by the user property. Default value: nil. This property is mandatory if user is specified on Windows and may only be specified if user is specified. The sensitive property for this resource will automatically be set to true if password is specified.

domain
Ruby Type: String

Windows only: The domain of the user user specified by the user property. Default value: nil. If not specified, the user name and password specified by the user and password properties will be used to resolve that user against the domain in which the system running Chef client is joined, or if that system is not joined to a domain it will resolve the user as a local account on that system. An alternative way to specify the domain is to leave this property unspecified and specify the domain as part of the user property.

umask
Ruby Type: String, Integer

The file mode creation mask, or umask.


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.

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.

Guard Interpreter

Any resource that passes a string command may also specify the interpreter that will be used to evaluate that string command. This is done by using the guard_interpreter property to specify a script-based resource.

Attributes

The guard_interpreter property may be set to any of the following values:

:bash

Evaluates a string command using the bash resource.

:batch

Evaluates a string command using the batch resource. Default value (within a batch resource block): :batch.

:csh

Evaluates a string command using the csh resource.

:default

Default. Executes the default interpreter as identified by Chef Infra Client.

:perl

Evaluates a string command using the perl resource.

:powershell_script

Evaluates a string command using the powershell_script resource. Default value (within a powershell_script resource block): :powershell_script.

:python

Evaluates a string command using the python resource.

:ruby

Evaluates a string command using the ruby resource.

Inheritance

The guard_interpreter property is set to :default by default for the bash, csh, perl, python, and ruby resources. When the guard_interpreter property is set to :default, not_if or only_if guard statements do not inherit properties that are defined by the script-based resource.

Warning

The batch and powershell_script resources inherit properties by default. The guard_interpreter property is set to :batch or :powershell_script automatically when using a not_if or only_if guard statement within a batch or powershell_script resource, respectively.

For example, the not_if guard statement in the following resource example does not inherit the environment property:

bash 'javatooling' do
  environment 'JAVA_HOME' => '/usr/lib/java/jdk1.7/home'
  code 'java-based-daemon-ctl.sh -start'
  not_if 'java-based-daemon-ctl.sh -test-started'
end

and requires adding the environment property to the not_if guard statement so that it may use the JAVA_HOME path as part of its evaluation:

bash 'javatooling' do
  environment 'JAVA_HOME' => '/usr/lib/java/jdk1.7/home'
  code 'java-based-daemon-ctl.sh -start'
  not_if 'java-based-daemon-ctl.sh -test-started', :environment => 'JAVA_HOME' => '/usr/lib/java/jdk1.7/home'
end

To inherit properties, add the guard_interpreter property to the resource block and set it to the appropriate value:

  • :bash for bash
  • :csh for csh
  • :perl for perl
  • :python for python
  • :ruby for ruby

For example, using the same example as from above, but this time adding the guard_interpreter property and setting it to :bash:

bash 'javatooling' do
  guard_interpreter :bash
  environment 'JAVA_HOME' => '/usr/lib/java/jdk1.7/home'
  code 'java-based-daemon-ctl.sh -start'
  not_if 'java-based-daemon-ctl.sh -test-started'
end

The not_if statement now inherits the environment property and will use the JAVA_HOME path as part of its evaluation.

Example

For example, the following code block will ensure the command is evaluated using the default interpreter as identified by Chef Infra Client:

resource 'name' do
  guard_interpreter :default
  # code
end

Examples

The following examples demonstrate various approaches for using the script resource in recipes:

Use a named provider to run a script

bash 'install_something' do
  user 'root'
  cwd '/tmp'
  code <<-EOH
    wget http://www.example.com/tarball.tar.gz
    tar -zxf tarball.tar.gz
    cd tarball
    ./configure
    make
    make   install
  EOH
end

Run a script

script 'install_something' do
  interpreter 'bash'
  user 'root'
  cwd '/tmp'
  code <<-EOH
    wget http://www.example.com/tarball.tar.gz
    tar -zxf tarball.tar.gz
    cd tarball
    ./configure
    make
    make install
  EOH
end

or something like:

bash 'openvpn-server-key' do
  environment('KEY_CN' => 'server')
  code <<-EOF
    openssl req -batch -days #{node['openvpn']['key']['expire']} \
      -nodes -new -newkey rsa:#{key_size} -keyout #{key_dir}/server.key \
      -out #{key_dir}/server.csr -extensions server \
      -config #{key_dir}/openssl.cnf
  EOF
  not_if { File.exist?('#{key_dir}/server.crt') }
end

where code contains the OpenSSL command to be run. The not_if property tells Chef Infra Client not to run the command if the file already exists.

Install a file from a remote location using bash

The following is an example of how to install the foo123 module for Nginx. This module adds shell-style functionality to an Nginx configuration file and does the following:

  • Declares three variables
  • Gets the Nginx file from a remote location
  • Installs the file using Bash to the path specified by the src_filepath variable
# the following code sample is similar to the ``upload_progress_module``
# recipe in the ``nginx`` cookbook:
# https://github.com/chef-cookbooks/nginx

src_filename = "foo123-nginx-module-v#{
  node['nginx']['foo123']['version']
}.tar.gz"
src_filepath = "#{Chef::Config['file_cache_path']}/#{src_filename}"
extract_path = "#{
  Chef::Config['file_cache_path']
  }/nginx_foo123_module/#{
  node['nginx']['foo123']['checksum']
}"

remote_file 'src_filepath' do
  source node['nginx']['foo123']['url']
  checksum node['nginx']['foo123']['checksum']
  owner 'root'
  group 'root'
  mode '0755'
end

bash 'extract_module' do
  cwd ::File.dirname(src_filepath)
  code <<-EOH
    mkdir -p #{extract_path}
    tar xzf #{src_filename} -C #{extract_path}
    mv #{extract_path}/*/* #{extract_path}/
  EOH
  not_if { ::File.exist?(extract_path) }
end

Install an application from git using bash

The following example shows how Bash can be used to install a plug-in for rbenv named ruby-build, which is located in git version source control. First, the application is synchronized, and then Bash changes its working directory to the location in which ruby-build is located, and then runs a command.

git "#{Chef::Config[:file_cache_path]}/ruby-build" do
  repository 'git://github.com/sstephenson/ruby-build.git'
  revision 'master'
  action :sync
end

bash 'install_ruby_build' do
  cwd "#{Chef::Config[:file_cache_path]}/ruby-build"
  user 'rbenv'
  group 'rbenv'
  code <<-EOH
    ./install.sh
  EOH
  environment 'PREFIX' => '/usr/local'
end

To read more about ruby-build, see here: https://github.com/sstephenson/ruby-build.

Store certain settings

The following recipe shows how an attributes file can be used to store certain settings. An attributes file is located in the attributes/ directory in the same cookbook as the recipe which calls the attributes file. In this example, the attributes file specifies certain settings for Python that are then used across all nodes against which this recipe will run.

Python packages have versions, installation directories, URLs, and checksum files. An attributes file that exists to support this type of recipe would include settings like the following:

default['python']['version'] = '2.7.1'

if python['install_method'] == 'package'
  default['python']['prefix_dir'] = '/usr'
else
  default['python']['prefix_dir'] = '/usr/local'
end

default['python']['url'] = 'http://www.python.org/ftp/python'
default['python']['checksum'] = '80e387...85fd61'

and then the methods in the recipe may refer to these values. A recipe that is used to install Python will need to do the following:

  • Identify each package to be installed (implied in this example, not shown)
  • Define variables for the package version and the install_path
  • Get the package from a remote location, but only if the package does not already exist on the target system
  • Use the bash resource to install the package on the node, but only when the package is not already installed
#  the following code sample comes from the ``oc-nginx`` cookbook on |github|: https://github.com/cookbooks/oc-nginx

version = node['python']['version']
install_path = "#{node['python']['prefix_dir']}/lib/python#{version.split(/(^\d+\.\d+)/)[1]}"

remote_file "#{Chef::Config[:file_cache_path]}/Python-#{version}.tar.bz2" do
  source "#{node['python']['url']}/#{version}/Python-#{version}.tar.bz2"
  checksum node['python']['checksum']
  mode '0755'
  not_if { ::File.exist?(install_path) }
end

bash 'build-and-install-python' do
  cwd Chef::Config[:file_cache_path]
  code <<-EOF
    tar -jxvf Python-#{version}.tar.bz2
    (cd Python-#{version} && ./configure #{configure_options})
    (cd Python-#{version} && make && make install)
  EOF
  not_if { ::File.exist?(install_path) }
end

Run a command as an alternate user

Note: When Chef is running as a service, this feature requires that the user that Chef runs as has ‘SeAssignPrimaryTokenPrivilege’ (aka ‘SE_ASSIGNPRIMARYTOKEN_NAME’) user right. By default only LocalSystem and NetworkService have this right when running as a service. This is necessary even if the user is an Administrator.

This right can be added and checked in a recipe using this example:

# Add 'SeAssignPrimaryTokenPrivilege' for the user
Chef::ReservedNames::Win32::Security.add_account_right('<user>', 'SeAssignPrimaryTokenPrivilege')

# Check if the user has 'SeAssignPrimaryTokenPrivilege' rights
Chef::ReservedNames::Win32::Security.get_account_right('<user>').include?('SeAssignPrimaryTokenPrivilege')

The following example shows how to run mkdir test_dir from a Chef Infra Client run as an alternate user.

# Passing only username and password
script 'mkdir test_dir' do
 interpreter "bash"
 code  "mkdir test_dir"
 cwd Chef::Config[:file_cache_path]
 user "username"
 password "password"
end

# Passing username and domain
script 'mkdir test_dir' do
 interpreter "bash"
 code  "mkdir test_dir"
 cwd Chef::Config[:file_cache_path]
 domain "domain-name"
 user "username"
 password "password"
end

# Passing username = 'domain-name\\username'. No domain is passed
script 'mkdir test_dir' do
 interpreter "bash"
 code  "mkdir test_dir"
 cwd Chef::Config[:file_cache_path]
 user "domain-name\\username"
 password "password"
end

# Passing username = 'username@domain-name'. No domain is passed
script 'mkdir test_dir' do
 interpreter "bash"
 code  "mkdir test_dir"
 cwd Chef::Config[:file_cache_path]
 user "username@domain-name"
 password "password"
end