Augments
An augments file can be used to define variables and classes to the execution of all CFEngine components before any parsing or evaluation happen. It's a JSON data file, so you should view and edit it with a JSON-aware editor if possible.This is a convenient way to override defaults defined in the Masterfiles Policy Framework without modifying the shipped policy itself.
The file def.json
is found like the policy file to be run:
- with no arguments, it's in
$(sys.inputdir)/def.json
because$(sys.inputdir)/promises.cf
is used - with
-f /dirname/myfile.cf
, it's in/dirname/def.json
- with
-f ./myfile.cf
, it's in./def.json
Values will be expanded, so you can use the variables from Special Variables.
An augments file can contain the following keys:
inputs
Any filenames you put here will appear in the def.augments_inputs
variable.
The standard set of masterfiles refers to this variable and will autoload those
files.
vars
Any variables you put here will be put in the def
bundle scope. Thus:
"vars":
{
"phone": "22-333-4444",
"myplatform": "$(sys.os)",
}
results in the variable def.phone
with value 22-333-4444
being defined, and
def.myplatform
with the value of your current OS. Again, note that this
happens before policy is parsed or evaluated.
You can see the list of variables thus defined in the output of cf-promises
--show-vars
(see Components and Common Control). They will be tagged with
the tag source=augments_file
. For instance, the above two variables (assuming
you placed the data in $(sys.inputdir)/def.json
) result in
cf-promises --show-vars=default:def
...
default:def.myplatform linux source=augments_file
default:def.phone 22-333-4444 source=augments_file
Variables of other types than string can be defined too, like in this example
"vars" : {
"str1" : "string 1",
"num1" : 5,
"num2" : 3.5
"slist1" : ["sliststr1", "sliststr2"]
"array1" : {
"idx1" : "val1",
"idx2" : "val2"
}
}
classes
Any class defined via augments will be evaluated and installed as
hard classes. Each element
of the array is tested against currently defined classes
as an anchored regular expression unless the string ends with ::
indicating it should be interpreted as a
class expression.
Note that augments is processed at the very beginning of agent evaluation. You can use any hard classes, persistent classes , or classes defined earlier in the augments list. Test carefully, custom soft classes may not be defined early enough for use. Thus:
"classes":
{
"augments_class_from_regex_my_always": [ "any" ],
"augments_class_from_regex_my_other_apache": [ "server[34]", "debian.*" ],
"augments_class_from_regex_my_other_always": [ "augments_class_from_regex_my_always" ],
"augments_class_from_regex_when_MISSING_not_defined": [ "^(?!MISSING).*" ]
"augments_class_from_regex": [ "cfengine_\\d+" ],
"augments_class_from_single_class_as_regex": [ "cfengine" ],
"augments_class_from_single_class_as_expression": [ "cfengine::" ],
"augments_class_from_classexpression_and": [ "cfengine.cfengine_3::" ],
"augments_class_from_classexpression_not": [ "!MISSING::" ],
"augments_class_from_classexpression_or": [ "cfengine|cfengine_3::" ],
"augments_class_from_classexpression_complex": [ "(cfengine|cfengine_3).!MISSING::" ]
}
results in
* augments_class_from_rgex_my_always
being always defined.
augments_class_from_regex_my_other_apache
will be defined if the classesserver3
orserver4
are defined, or if any class starting withdebian
is defined.augments_class_from_regex_my_other_always
will be defined becauseaugments_class_from_regex_my_always
is listed first and always defined.augments_class_from_regex_when_MISSING_not_defined
will be defined if the classMISSING
is not defined.augments_class_from_single_class_as_regex
will be defined because the classcfengine
is always defined.augments_class_from_single_class_as_expression
will be defined becausecfengine
is defined when interpreted as a class expression.augments_class_from_classexpression_and
will be defined because the classcfengine
and the classcfengine_3
are defined and the class expressioncfengine.cfengine_3::
evaluates to true.augments_class_from_classexpression_not
will be defined because the class expression!MISSING::
evaluates to false since the classMISSING
is not defined.augments_class_from_classexpression_or
will be defined because the class expressioncfengine|cfengine_3::
evaluates to true since at least one ofcfengine
orcfengine_3
will always be defined by cfengine 3 agents.augments_class_from_classexpression_complex
will be defined because the class expression(cfengine|cfengine_3).!MISSING::
evaluates to true since at least one ofcfengine
orcfengine_3
will always be defined by cfengine 3 agents andMISSING
is not defined.
You can see the list of classes thus defined through def.json
in the output
of cf-promises --show-classes
(see Components and Common Control). They
will be tagged with the tags source=augments_file,hardclass
. For instance:
% cf-promises --show-classes=my_
...
augments_class_from_regex_my_always source=augments_file,hardclass
augments_class_from_regex_my_other_always source=augments_file,hardclass
augments_class_from_regex_my_other_apache source=augments_file,hardclass
See also:
- Functions that use regular expressions with classes:
classesmatching()
,classmatch()
,countclassesmatching()
augments
A list of file names that should be merged using mergedata()
semantic
Example:
Here we merge a platform specific augments on to the def.json
loaded next to
the policy entry and see what the resulting variable values will
be.
The def.json
next to the policy entry:
{
"vars":{
"my_var": "defined in def.json",
"my_other_var": "Defined ONLY in def.json"
},
"augments": [
"/var/cfengine/augments/$(sys.flavor).json"
]
}
The platform specific augments on a CentOS 6 host:
/var/cfengine/augments/centos_6.json
:
{
"vars": {
"my_var": "Overridden in centos_6.json",
"centos_6_var": "Defined ONLY in centos_6.json"
}
}
The expected values of the variables defined in the def bundle scope:
R: def.my_var == Overridden in centos_6.json
R: def.my_other_var == Defined ONLY in def.json
R: def.centos_6_var == Defined ONLY in centos_6.json
History
- 3.12.2, 3.14.0 introduced class expression interpretation (
::
suffix) to classes key - 3.12.0 introduced the
augments
key - 3.7.3 back port
def.json
parsing in core agent and loaddef.json
if present next to policy entry - 3.8.2 removed core support for
inputs
key, loaddef.json
if present next to policy entry - 3.8.1
def.json
parsing moved from policy to core agent for resolution of classes and variables to be able to affect control bodies - 3.7.0 introduced augments concept into the Masterfiles Policy Framework