cron Resource
This page is generated from the Chef Infra Client source code.To suggest a change, edit the cron.rb file and submit a pull request to the Chef Infra Client repository.
Use the cron resource to manage cron entries for time-based job scheduling. Properties for a schedule will default to * if not provided. The cron resource requires access to a crontab program, typically cron.
Warning
The cron resource should only be used to modify an entry in a crontab file. The cron_d
resource directly manages cron.d
files. This resource ships in Chef Infra Client 14.4 or later and can also be found in the cron cookbook) for previous Chef Infra Client releases.
Syntax
The full syntax for all of the properties that are available to the cron resource is:
cron 'name' do
command String
day Integer, String # default value: "*"
environment Hash # default value: {}
home String
hour Integer, String # default value: "*"
mailto String
minute Integer, String # default value: "*"
month Integer, String # default value: "*"
path String
shell String
time Symbol
time_out Hash # default value: {}
user String # default value: "root"
weekday Integer, String, Symbol # default value: "*"
action Symbol # defaults to :create if not specified
end
where:
cron
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
,day
,environment
,home
,hour
,mailto
,minute
,month
,path
,shell
,time
,time_out
,user
, andweekday
are the properties available to this resource.
Actions
The cron resource has the following actions:
:create
- Create an entry in a cron table file (crontab). If an entry already exists (but does not match), update that entry to match. (default)
:delete
- Delete an entry from a cron table file (crontab).
: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.
Properties
The cron resource has the following properties:
command
- Ruby Type: String |
REQUIRED
The command to be run, or the path to a file that contains the command to be run.
day
- Ruby Type: Integer, String | Default Value:
*
The day of month at which the cron entry should run (
1 - 31
).
environment
- Ruby Type: Hash | Default Value:
{}
A Hash containing additional arbitrary environment variables under which the cron job will be run in the form of
({'ENV_VARIABLE' => 'VALUE'})
. Note: These variables must exist for a command to be run successfully.
home
- Ruby Type: String
Set the
HOME
environment variable.
hour
- Ruby Type: Integer, String | Default Value:
*
The hour at which the cron entry is to run (
0 - 23
).
mailto
- Ruby Type: String
Set the
MAILTO
environment variable.
minute
- Ruby Type: Integer, String | Default Value:
*
The minute at which the cron entry should run (
0 - 59
).
month
- Ruby Type: Integer, String | Default Value:
*
The month in the year on which a cron entry is to run (
1 - 12
,jan-dec
, or*
).
path
- Ruby Type: String
Set the
PATH
environment variable.
shell
- Ruby Type: String
Set the
SHELL
environment variable.
time
- Ruby Type: SymbolAllowed Values:
:annually, :daily, :hourly, :midnight, :monthly, :reboot, :weekly, :yearly
A time interval.
time_out
- Ruby Type: Hash | Default Value:
{}
A Hash of timeouts in the form of
({'OPTION' => 'VALUE'})
. Accepted valid options are:preserve-status
(BOOL, default: ‘false’),foreground
(BOOL, default: ‘false’),kill-after
(in seconds),signal
(a name like ‘HUP’ or a number)
New in Chef Infra Client 15.7
user
- Ruby Type: String | Default Value:
root
The name of the user that runs the command. If the user property is changed, the original user for the crontab program continues to run until that crontab program is deleted. This property is not applicable on the AIX platform.
weekday
- Ruby Type: Integer, String, Symbol | Default Value:
*
The day of the week on which this entry is to run (
0-7
,mon-sun
,monday-sunday
, or*
), where Sunday is both0
and7
.
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 cron resource in recipes:
Run a program at a specified interval
cron 'noop' do
hour '5'
minute '0'
command '/bin/true'
end
Run an entry if a folder exists
cron 'ganglia_tomcat_thread_max' do
command "/usr/bin/gmetric
-n 'tomcat threads max'
-t uint32
-v '/usr/local/bin/tomcat-stat --thread-max'"
only_if { ::File.exist?('/home/jboss') }
end
Run every Saturday, 8:00 AM
The following example shows a schedule that will run every hour at 8:00 each Saturday morning, and will then send an email to “admin@example.com” after each run.
cron 'name_of_cron_entry' do
minute '0'
hour '8'
weekday '6'
mailto 'admin@example.com'
action :create
end
Run once a week
cron 'cookbooks_report' do
minute '0'
hour '0'
weekday '1'
user 'chefio'
mailto 'sysadmin@example.com'
home '/srv/supermarket/shared/system'
command %W{
cd /srv/supermarket/current &&
env RUBYLIB="/srv/supermarket/current/lib"
RAILS_ASSET_ID=`git rev-parse HEAD` RAILS_ENV="#{rails_env}"
bundle exec rake cookbooks_report
}.join(' ')
action :create
end
Run only in November
The following example shows a schedule that will run at 8:00 PM, every weekday (Monday through Friday), but only in November:
cron 'name_of_cron_entry' do
minute '0'
hour '20'
day '*'
month '11'
weekday '1-5'
action :create
end