execute Resource
This page is generated from the Chef Infra Client source code.To suggest a change, edit the execute.rb file and submit a pull request to the Chef Infra Client repository.
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.
Note
Use the script resource to execute a script using a specific interpreter (Ruby, Python, Perl, csh, or Bash).
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
, anduser
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
andpassword
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
oruser@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 (theconverge 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 anotifies
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 returntrue
in addition to0
. - A block is executed as Ruby code that must return either
true
orfalse
. If the block returnstrue
, the guard property is applied. If the block returnsfalse
, 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.
PropertiesThe 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:
Warning
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