execute Resource

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Use the execute resource to execute a single command. 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

An execute resource block typically executes a single command that is unique to the environment in which a recipe will run. Some execute resource commands are run by themselves, but often they are run in combination with other Chef resources. For example, a single command that is run by itself:

execute 'apache_configtest' do
  command '/usr/sbin/apachectl configtest'
end

where:

• '/usr/sbin/apachectl configtest' is a command that tests if the configuration files for Apache are valid.

  Commands are often run in combination with other Chef resources. The following example shows the template resource run with the execute resource to add an entry to a LDAP Directory Interchange Format (LDIF) file:

  execute 'slapadd' do command 'slapadd < /tmp/something.ldif' creates '/var/lib/slapd/uid.bdb' action :nothing
  end
  
  template '/tmp/something.ldif' do source 'something.ldif' notifies :run, 'execute[slapadd]', :immediately
  end
  

  where

• '/tmp/something.ldif' specifies the location of the file
• 'something.ldif' specifies template file from which /tmp/something.ldif is created
• 'slapadd < /tmp/something.ldif' is the command that is run
• /var/lib/slapd/uid.bdb prevents the execute resource block from running if that file already exists

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

execute 'name' do
  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
  group            String, Integer
  input            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:

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

Actions

The execute 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 execute resource has the following properties:

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.

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.

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 execute resource in recipes:

Run a command upon notification:

execute 'slapadd' do
  command 'slapadd < /tmp/something.ldif'
  creates '/var/lib/slapd/uid.bdb'

  action :nothing
end

template '/tmp/something.ldif' do
  source 'something.ldif'

  notifies :run, 'execute[slapadd]', :immediately
end

Run a touch file only once while running a command:

execute 'upgrade script' do
  command 'php upgrade-application.php && touch /var/application/.upgraded'

  creates '/var/application/.upgraded'
  action :run
end

Run a command which requires an environment variable:

execute 'slapadd' do
  command 'slapadd < /tmp/something.ldif'
  creates '/var/lib/slapd/uid.bdb'

  action :run
  environment ({'HOME' => '/home/my_home'})
end

Delete a repository using yum to scrub the cache:

# the following code sample thanks to gaffneyc @ https://gist.github.com/918711
execute 'clean-yum-cache' do
  command 'yum clean all'
  action :nothing
end

file '/etc/yum.repos.d/bad.repo' do
  action :delete
  notifies :run, 'execute[clean-yum-cache]', :immediately
end

Prevent restart and reconfigure if configuration is broken:

Use the :nothing action (common to all resources) to prevent the test from starting automatically, and then use the subscribes notification to run a configuration test when a change to the template is detected.

execute 'test-nagios-config' do
  command 'nagios3 --verify-config'
  action :nothing
  subscribes :run, 'template[/etc/nagios3/configures-nagios.conf]', :immediately
end

Notify in a specific order:

To notify multiple resources, and then have these resources run in a certain order, do something like the following.

execute 'foo' do
  command '...'
  notifies :create, 'template[baz]', :immediately
  notifies :install, 'package[bar]', :immediately
  notifies :run, 'execute[final]', :immediately
end

template 'baz' do
  #...
  notifies :run, 'execute[restart_baz]', :immediately
end

package 'bar'
  execute 'restart_baz'
  execute 'final' do
  command '...'
end

where the sequencing will be in the same order as the resources are listed in the recipe: execute 'foo', template 'baz', execute [restart_baz], package 'bar', and execute 'final'.

Execute a command using a template:

The following example shows how to set up IPv4 packet forwarding using the execute resource to run a command named forward_ipv4 that uses a template defined by the template resource.

execute 'forward_ipv4' do
  command 'echo > /proc/.../ipv4/ip_forward'
  action :nothing
end

template '/etc/file_name.conf' do
  source 'routing/file_name.conf.erb'

 notifies :run, 'execute[forward_ipv4]', :delayed
end

where the command property for the execute resource contains the command that is to be run and the source property for the template resource specifies which template to use. The notifies property for the template specifies that the execute[forward_ipv4] (which is defined by the execute resource) should be queued up and run at the end of a Chef Infra Client run.

Add a rule to an IP table:

The following example shows how to add a rule named test_rule to an IP table using the execute resource to run a command using a template that is defined by the template resource:

execute 'test_rule' do
  command "command_to_run
    --option value
    --option value
    --source #{node[:name_of_node][:ipsec][:local][:subnet]}
    -j test_rule"

  action :nothing
end

template '/etc/file_name.local' do
  source 'routing/file_name.local.erb'
  notifies :run, 'execute[test_rule]', :delayed
end

where the command property for the execute resource contains the command that is to be run and the source property for the template resource specifies which template to use. The notifies property for the template specifies that the execute[test_rule] (which is defined by the execute resource) should be queued up and run at the end of a Chef Infra Client run.

Stop a service, do stuff, and then restart it:

The following example shows how to use the execute, service, and mount resources together to ensure that a node running on Amazon EC2 is running MySQL. This example does the following:

• Checks to see if the Amazon EC2 node has MySQL
• If the node has MySQL, stops MySQL
• Installs MySQL
• Mounts the node
• Restarts MySQL

# the following code sample comes from the ``server_ec2``
# recipe in the following cookbook:
# https://github.com/chef-cookbooks/mysql

if (node.attribute?('ec2') && !FileTest.directory?(node['mysql']['ec2_path']))
  service 'mysql' do
    action :stop
  end

  execute 'install-mysql' do
    command "mv #{node['mysql']['data_dir']} #{node['mysql']['ec2_path']}"
    not_if { ::File.directory?(node['mysql']['ec2_path']) }
  end

  [node['mysql']['ec2_path'], node['mysql']['data_dir']].each do |dir|
    directory dir do
      owner 'mysql'
      group 'mysql'
    end
  end

  mount node['mysql']['data_dir'] do
    device node['mysql']['ec2_path']
    fstype 'none'
    options 'bind,rw'
    action [:mount, :enable]
  end

  service 'mysql' do
    action :start
  end
end

where

• the two service resources are used to stop, and then restart the MySQL service
• the execute resource is used to install MySQL
• the mount resource is used to mount the node and enable MySQL

Use the platform_family? method:

The following is an example of using the platform_family? method in the Recipe DSL to create a variable that can be used with other resources in the same recipe. In this example, platform_family? is being used to ensure that a specific binary is used for a specific platform before using the remote_file resource to download a file from a remote location, and then using the execute resource to install that file by running a command.

if platform_family?('rhel')
  pip_binary = '/usr/bin/pip'
else
  pip_binary = '/usr/local/bin/pip'
end

remote_file "#{Chef::Config[:file_cache_path]}/distribute_setup.py" do
  source 'http://python-distribute.org/distribute_setup.py'
  mode '0755'
  not_if { ::File.exist?(pip_binary) }
end

execute 'install-pip' do
  cwd Chef::Config[:file_cache_path]
  command <<~EOF
    # command for installing Python goes here
  EOF
  not_if { ::File.exist?(pip_binary) }
end

where a command for installing Python might look something like:

#{node['python']['binary']} distribute_setup.py #{::File.dirname(pip_binary)}/easy_install pip

Control a service using the execute resource:

Do something like this:

service 'tomcat' do
  action :start
end

and NOT something like this:

execute 'start-tomcat' do
  command '/etc/init.d/tomcat start'
  action :run
end

There is no reason to use the execute resource to control a service because the service resource exposes the start_command property directly, which gives a recipe full control over the command issued in a much cleaner, more direct manner.

Use the search Infra Language helper to find users:

The following example shows how to use the search method in the Chef Infra Language to search for users:

#  the following code sample comes from the openvpn cookbook:

search("users", "*:*") do |u|
  execute "generate-openvpn-#{u['id']}" do
    command "./pkitool #{u['id']}"
    cwd '/etc/openvpn/easy-rsa'
  end

  %w{ conf ovpn }.each do |ext|
    template "#{node['openvpn']['key_dir']}/#{u['id']}.#{ext}" do
      source 'client.conf.erb'
      variables :username => u['id']
    end
  end
end

where

• the search data will be used to create execute resources
• the template resource tells Chef Infra Client which template to use

Enable remote login for macOS:

execute 'enable ssh' do
  command '/usr/sbin/systemsetup -setremotelogin on'
  not_if '/usr/sbin/systemsetup -getremotelogin | /usr/bin/grep On'
  action :run
end

Execute code immediately, based on the template resource:

By default, notifications are :delayed, that is they are queued up as they are triggered, and then executed at the very end of a Chef Infra Client run. To run an action immediately, use :immediately:

template '/etc/nagios3/configures-nagios.conf' do
  # other parameters
  notifies :run, 'execute[test-nagios-config]', :immediately
end

and then Chef Infra Client would immediately run the following:

execute 'test-nagios-config' do
  command 'nagios3 --verify-config'
  action :nothing
end

Sourcing a file:

The execute resource cannot be used to source a file (e.g. command 'source filename'). The following example will fail because source is not an executable:

execute 'foo' do
  command 'source /tmp/foo.sh'
end

Instead, use the script resource or one of the script-based resources (bash, csh, perl, python, or ruby). For example:

bash 'foo' do
  code 'source /tmp/foo.sh'
end

Run a Knife command:

execute 'create_user' do
  command <<~EOM
    knife user create #{user}
      --admin
      --password password
      --disable-editing
      --file /home/vagrant/.chef/user.pem
      --config /tmp/knife-admin.rb
    EOM
end

Run install command into virtual environment:

The following example shows how to install a lightweight JavaScript framework into Vagrant:

execute "install q and zombiejs" do
  cwd "/home/vagrant"
  user "vagrant"
  environment ({'HOME' => '/home/vagrant', 'USER' => 'vagrant'})
  command "npm install -g q zombie should mocha coffee-script"
  action :run
end

Run a command as a named user:

The following example shows how to run bundle install from a Chef Infra Client run as a specific user. This will put the gem into the path of the user (vagrant) instead of the root user (under which the Chef Infra Client runs):

execute '/opt/chefdk/embedded/bin/bundle install' do
  cwd node['chef_workstation']['bundler_path']
  user node['chef_workstation']['user']

  environment ({
    'HOME' => "/home/#{node['chef_workstation']['user']}",
    'USER' => node['chef_workstation']['user']
  })
  not_if 'bundle check'
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
execute 'mkdir test_dir' do
  cwd Chef::Config[:file_cache_path]

  user "username"
  password "password"
end

# Passing username and domain
execute 'mkdir test_dir' do
  cwd Chef::Config[:file_cache_path]

  domain "domain-name"
  user "user"
  password "password"
end

# Passing username = 'domain-name\username'. No domain is passed
execute 'mkdir test_dir' do
  cwd Chef::Config[:file_cache_path]

  user "domain-name\username"
  password "password"
end

# Passing username = 'username@domain-name'.  No domain is passed
execute 'mkdir test_dir' do
  cwd Chef::Config[:file_cache_path]

  user "username@domain-name"
  password "password"
end

Run a command with an external input file:

execute ‘md5sum’ do input File.read(FILE) end