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bash Resource

This page is generated from the Chef Infra Client source code.
To suggest a change, edit the bash.rb file and submit a pull request to the Chef Infra Client repository.

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Use the bash resource to execute scripts using the Bash interpreter. 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.

Syntax

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

bash 'name' do
  code             String
  command          String, Array # default value: 'name' unless specified
  creates          String
  cwd              String
  default_env      true, false # default value: false
  domain           String
  elevated         true, false # default value: false
  environment      Hash
  flags            String
  group            String, Integer
  input            String
  interpreter      String
  live_stream      true, false # default value: false
  login            true, false # default value: false
  password         String
  returns          Integer, Array # default value: 0
  timeout          Integer, String, Float # default value: 3600
  user             String, Integer
  action           Symbol # defaults to :run if not specified
end

where:

  • bash 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.
  • code, command, creates, cwd, default_env, domain, elevated, environment, flags, group, input, interpreter, live_stream, login, password, returns, timeout, and user are the properties available to this resource.

Actions

The bash resource has the following actions:

: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.
:run
Run a command. (default)

Properties

The bash resource has the following properties:

code
Ruby Type: String | REQUIRED

A quoted string of code to be executed.

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

An optional property to set the command to be executed if it differs from the resource block’s name.

Note

Use the execute resource to run a single command. Use multiple execute resource blocks to run multiple commands.

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.

default_env
Ruby Type: true, false | Default Value: false

When true this enables ENV magic to add path_sanity to the PATH and force the locale to English+UTF-8 for parsing output.

New in Chef Client 14.2

domain
Ruby Type: String

Windows only: The domain of the user specified by the user property. If not specified, the username 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 Infra 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.

New in Chef Client 12.21

elevated
Ruby Type: true, false | Default Value: false

Determines whether the script will run with elevated permissions to circumvent User Access Control (UAC) from interactively blocking the process. This will cause the process to be run under a batch login instead of an interactive login. The user running chef-client needs the ‘Replace a process level token’ and ‘Adjust Memory Quotas for a process’ permissions. The user that is running the command needs the ‘Log on as a batch job’ permission. Because this requires a login, the user and password properties are required.

New in Chef Client 13.3

environment
Ruby Type: Hash

A Hash of environment variables in the form of ({'ENV_VARIABLE' => 'VALUE'}). Note: 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.

input
Ruby Type: String

An optional property to set the input sent to the command as STDIN.

New in Chef Infra Client 16.2

live_stream
Ruby Type: true, false | Default Value: false

Send the output of the command run by this execute resource block to the Chef Infra Client event stream.

login
Ruby Type: true, false | Default Value: false

Use a login shell to run the commands instead of inheriting the existing execution environment.

New in Chef Infra Client 17.0

password
Ruby Type: String

Windows only: The password of the user specified by the user property. 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.

New in Chef Client 12.21

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, String, Float | Default Value: 3600

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

user
Ruby Type: String, Integer

The user name of the user identity with which to launch the new process. The user name may optionally be specified with a domain, i.e. domain\user 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 property. On Windows only, if this property is specified, the password property must be specified.

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.

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 bash resource in recipes:

Compile an application

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

Using escape characters in a string of code

In the following example, the find command uses an escape character (\). Use a second escape character (\\) to preserve the escape character in the code string:

bash 'delete some archives ' do
  code <<-EOH
    find ./ -name "*.tar.Z" -mtime +180 -exec rm -f {} \\;
  EOH
  ignore_failure true
end

Install a file from a remote location

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
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

git "#{Chef::Config[:file_cache_path]}/ruby-build" do
  repository 'git://github.com/rbenv/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

Using Attributes in Bash Code

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
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
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