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.
Note
The bash script resource (which is based on the script resource) is different from the ruby_block resource because Ruby code that is run with this resource is created as a temporary file and executed like other script resources, rather than run inline.
A bash resource block executes scripts using Bash:
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
where
cwd
specifies the directory from which the command is runcode
specifies the command to runThe full syntax for all of the properties that are available to the bash resource is:
bash 'name' do code String creates String cwd String environment Hash flags String group String, Integer notifies # see description path Array provider Chef::Provider::Script::Bash returns Integer, Array subscribes # see description timeout Integer, Float user String, Integer umask String, Integer action Symbol # defaults to :run if not specified end
where
bash
is the resourcename
is the name of the resource blockcwd
is the location from which the command is run:action
identifies the steps the chef-client will take to bring the node into the desired statecode
, creates
, cwd
, environment
, flags
, group
, path
, provider
, returns
, timeout
, user
, 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.This resource has the following actions:
:nothing
:run
This 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.
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 Types: String, Integer
The group name or group ID that must be changed before running a command.
ignore_failure
Ruby Types: TrueClass, FalseClass
Continue running a recipe if a resource fails for any reason. Default value: false
.
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 notifiy more than one resource; use a notifies
statement for each resource to be notified.
A timer specifies the point during the chef-client run at which a notification is run. The following timers are available:
:before
:delayed
:immediate
, :immediately
The syntax for notifies
is:
notifies :action, 'resource[name]', :timer
path
Ruby Type: Array
An array of paths to use when searching for a command. These paths are not added to the command’s environment $PATH. The default value uses the system path.
Warning
For example:
bash 'mycommand' do environment 'PATH' => "/my/path/to/bin:#{ENV['PATH']}" end
provider
Ruby Type: Chef Class
Optional. Explicitly specifies a provider. See “Providers” section below for more information.
retries
Ruby Type: Integer
The number of times to catch exceptions and retry the resource. Default value: 0
.
retry_delay
Ruby Type: Integer
The retry delay (in seconds). Default value: 2
.
returns
Ruby Types: Integer, Array
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. Default value: 0
.
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.
A timer specifies the point during the chef-client run at which a notification is run. The following timers are available:
:before
:delayed
:immediate
, :immediately
The syntax for subscribes
is:
subscribes :action, 'resource[name]', :timer
timeout
Ruby Types: Integer, Float
The amount of time (in seconds) a command is to wait before timing out. Default value: 3600
.
user
Ruby Types: String, Integer
The user name or user ID that should be changed before running a command.
umask
Ruby Types: String, Integer
The file mode creation mask, or umask.
A guard property can be used to evaluate the state of a node during the execution phase of the chef-client run. Based on the results of this evaluation, a guard property is then used to tell the chef-client if it should continue executing a resource. A guard property accepts either a string value or a Ruby block value:
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
.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 the chef-client to do nothing.
Attributes
The following properties can be used to define a guard that is evaluated during the execution phase of the chef-client run:
not_if
true
.only_if
true
.Arguments
The following arguments can be used with the not_if
or only_if
guard properties:
:user
Specify the user that a command will run as. For example:
not_if 'grep adam /etc/passwd', :user => 'adam'
:group
Specify the group that a command will run as. For example:
not_if 'grep adam /etc/passwd', :group => 'adam'
:environment
Specify a Hash of environment variables to be set. For example:
not_if 'grep adam /etc/passwd', :environment => { 'HOME' => '/home/adam' }
:cwd
Set the current working directory before running a command. For example:
not_if 'grep adam passwd', :cwd => '/etc'
:timeout
Set a timeout for a command. For example:
not_if 'sleep 10000', :timeout => 10
Where a resource represents a piece of the system (and its desired state), a provider defines the steps that are needed to bring that piece of the system from its current state into the desired state.
The chef-client will determine the correct provider based on configuration data collected by Ohai at the start of the chef-client run. This configuration data is then mapped to a platform and an associated list of providers.
Generally, it’s best to let the chef-client choose the provider, and this is (by far) the most common approach. However, in some cases, specifying a provider may be desirable. There are two approaches:
yum_package "foo" do
instead of package "foo" do
, script "foo" do
instead of bash "foo" do
, and so on—when availableprovider
property within the resource block to specify the long name of the provider as a property of a resource. For example: provider Chef::Provider::Long::Name
This resource has the following providers:
Chef::Provider::Script
, script
Chef::Provider::Script::Bash
, bash
The following examples demonstrate various approaches for using resources in recipes. If you want to see examples of how Chef uses resources in recipes, take a closer look at the cookbooks that Chef authors and maintains: https://github.com/chef-cookbooks.
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
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:
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' reference '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:
version
and the install_path
# 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
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https://docs-archive.chef.io/release/12-13/resource_bash.html