execute resource¶
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).
Changed in 12.19 to support windows alternate user identity in execute resources.
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 # defaults to 'name' if not specified
creates String
cwd String
environment Hash # env is an alias for environment
group String, Integer
live_stream true, false
notifies # see description
returns Integer, Array
sensitive true, false
subscribes # see description
timeout Integer, Float
umask String, Integer
user String
password String
domain String
action Symbol # defaults to :run if not specified
end
where
execute
is the resourcename
is the name of the resource blockcommand
is the command to be runaction
identifies the steps the chef-client will take to bring the node into the desired statecommand
,creates
,cwd
,environment
,group
,live_stream
,returns
,sensitive
,timeout
,user
,password
,domain
andumask
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 execute 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 command.
Properties¶
This resource has the following properties:
command
Ruby Type: String, Array
The name of the command to be executed. Default value: the
name
of the resource block. See “Syntax” section above for more information.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 a command is 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.)group
Ruby Type: String, Integer
The group name or group ID that must be changed before running a command.
ignore_failure
Ruby Type: true, false | Default Value:
false
Continue running a recipe if a resource fails for any reason.
live_stream
Ruby Type: true, false | Default Value:
false
Send the output of the command run by this execute resource block to the chef-client event stream.
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.A timer specifies the point during the Chef 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 the Chef 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
retries
Ruby Type: Integer | Default Value:
0
The number of times to catch exceptions and retry the resource.
retry_delay
Ruby Type: Integer | Default Value:
2
The retry delay (in seconds).
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.
sensitive
Ruby Type: true, false | Default Value:
false
Ensure that sensitive resource data is not logged by the chef-client. Default value:
false
.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 thenginx
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 examplenginx
) when a change is detected.A timer specifies the point during the Chef 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 the Chef 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
timeout
Ruby Type: Integer, Float
The amount of time (in seconds) a command is to wait before timing out. Default value:
3600
.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 specifed 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.
Guards¶
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:
- 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 the chef-client to do nothing.
Note
When using the not_if
and only_if
guards with the execute resource, the guard’s environment is inherited from the resource’s environment. For example:
execute 'bundle install' do
cwd '/myapp'
not_if 'bundle check' # This is run from /myapp
end
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
- Prevent a resource from executing when the condition returns
true
. only_if
- Allow a resource to execute only if the condition returns
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
Examples¶
The following examples demonstrate various approaches for using resources 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/myhome'})
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
notifies :create, 'ruby_block[reload-internal-yum-cache]', :immediately
end
Install repositories from a file, trigger a command, and force the internal cache to reload
The following example shows how to install new Yum repositories from a file, where the installation of the repository triggers a creation of the Yum cache that forces the internal cache for the chef-client to reload:
execute 'create-yum-cache' do
command 'yum -q makecache'
action :nothing
end
ruby_block 'reload-internal-yum-cache' do
block do
Chef::Provider::Package::Yum::YumCache.instance.reload
end
action :nothing
end
cookbook_file '/etc/yum.repos.d/custom.repo' do
source 'custom'
mode '0755'
notifies :run, 'execute[create-yum-cache]', :immediately
notifies :create, 'ruby_block[reload-internal-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 the chef-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 the chef-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 do FileTest.directory?(node['mysql']['ec2_path']) end
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
This is an example of something that should NOT be done. Use the service resource to control a service, not 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/tomcat6 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 recipe DSL method to find users
The following example shows how to use the search
method in the Recipe DSL to search for users:
# the following code sample comes from the openvpn cookbook: https://github.com/chef-cookbooks/openvpn
search("users", "*:*") do |u|
execute "generate-openvpn-#{u['id']}" do
command "./pkitool #{u['id']}"
cwd '/etc/openvpn/easy-rsa'
environment(
'EASY_RSA' => '/etc/openvpn/easy-rsa',
'KEY_CONFIG' => '/etc/openvpn/easy-rsa/openssl.cnf',
'KEY_DIR' => node['openvpn']['key_dir'],
'CA_EXPIRE' => node['openvpn']['key']['ca_expire'].to_s,
'KEY_EXPIRE' => node['openvpn']['key']['expire'].to_s,
'KEY_SIZE' => node['openvpn']['key']['size'].to_s,
'KEY_COUNTRY' => node['openvpn']['key']['country'],
'KEY_PROVINCE' => node['openvpn']['key']['province'],
'KEY_CITY' => node['openvpn']['key']['city'],
'KEY_ORG' => node['openvpn']['key']['org'],
'KEY_EMAIL' => node['openvpn']['key']['email']
)
not_if { File.exist?("#{node['openvpn']['key_dir']}/#{u['id']}.crt") }
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
execute "create-openvpn-tar-#{u['id']}" do
cwd node['openvpn']['key_dir']
command <<-EOH
tar zcf #{u['id']}.tar.gz \
ca.crt #{u['id']}.crt #{u['id']}.key \
#{u['id']}.conf #{u['id']}.ovpn \
EOH
not_if { File.exist?("#{node['openvpn']['key_dir']}/#{u['id']}.tar.gz") }
end
end
where
- the search will use both of the execute resources, unless the condition specified by the
not_if
commands are met - the
environments
property in the first execute resource is being used to define values that appear as variables in the OpenVPN configuration - the template resource tells the chef-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-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 the chef-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.gsub(/\s+/, ' ').strip!
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-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-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-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