sysctl Resource
This page is generated from the Chef Infra Client source code.To suggest a change, edit the sysctl.rb file and submit a pull request to the Chef Infra Client repository.
Use the sysctl resource to set or remove kernel parameters using the sysctl
command line tool and configuration files in the system’s sysctl.d
directory. Configuration files managed by this resource are named 99-chef-KEYNAME.conf
.
New in Chef Infra Client 14.0.
Syntax
The full syntax for all of the properties that are available to the sysctl resource is:
sysctl 'name' do
comment Array, String # default value: []
conf_dir String # default value: "/etc/sysctl.d"
ignore_error true, false # default value: false
key String # default value: 'name' unless specified
value Array, String, Integer, Float
action Symbol # defaults to :apply if not specified
end
where:
sysctl
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.comment
,conf_dir
,ignore_error
,key
, andvalue
are the properties available to this resource.
Actions
The sysctl resource has the following actions:
:apply
- Set the kernel parameter and update the
sysctl
settings. (default) :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.
:remove
- Remove the kernel parameter and update the
sysctl
settings.
Properties
The sysctl resource has the following properties:
comment
- Ruby Type: Array, String | Default Value:
[]
Comments, placed above the resource setting in the generated file. For multi-line comments, use an array of strings, one per line.
New in Chef Infra Client 15.8
conf_dir
- Ruby Type: String | Default Value:
/etc/sysctl.d
The configuration directory to write the config to.
ignore_error
- Ruby Type: true, false | Default Value:
false
Ignore any errors when setting the value on the command line.
key
- Ruby Type: String | Default Value:
The resource block's name
The kernel parameter key in dotted format if it differs from the resource block’s name.
value
- Ruby Type: Array, String, Integer, Float |
REQUIRED
The value to set.
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 sysctl resource in recipes:
Set vm.swappiness:
sysctl 'vm.swappiness' do
value 19
end
Remove kernel.msgmax:
Note: This only removes the sysctl.d config for kernel.msgmax. The value will be set back to the kernel default value.
sysctl 'kernel.msgmax' do
action :remove
end
Adding Comments to sysctl configuration files:
sysctl 'vm.swappiness' do
value 19
comment "define how aggressively the kernel will swap memory pages."
end
This produces /etc/sysctl.d/99-chef-vm.swappiness.conf as follows:
# define how aggressively the kernel will swap memory pages.
vm.swappiness = 1
Converting sysctl settings from shell scripts:
Example of existing settings:
fs.aio-max-nr = 1048576 net.ipv4.ip_local_port_range = 9000 65500 kernel.sem = 250 32000 100 128
Converted to sysctl resources:
sysctl 'fs.aio-max-nr' do
value '1048576'
end
sysctl 'net.ipv4.ip_local_port_range' do
value '9000 65500'
end
sysctl 'kernel.sem' do
value '250 32000 100 128'
end