General template snippets - AWS CloudFormation
Base64 encoded UserData propertyBase64 encoded UserData property with AccessKey and SecretKeyParameters section with one literal string parameterParameters section with string parameter with regular expression constraintParameters section with number parameter with MinValue and MaxValue constraintsParameters section with number parameter with AllowedValues constraintParameters section with one literal CommaDelimitedList parameterParameters section with parameter value based on pseudo parameterMapping section with three mappingsDescription based on literal stringOutputs section with one literal string outputOutputs section with one resource reference and one pseudo reference outputOutputs section with an output based on a function, a literal string, a reference, and a pseudo parameterTemplate format versionAWSTags property

General template snippets

The following examples show different CloudFormation template features that aren't specific to an AWS service.

Base64 encoded UserData property

This example shows the assembly of a UserData property using the Fn::Base64 and Fn::Join functions. The references MyValue and MyName are parameters that must be defined in the Parameters section of the template. The literal string Hello World is just another value this example passes in as part of the UserData.

JSON

"UserData" : {
    "Fn::Base64" : {
        "Fn::Join" : [ ",", [
            { "Ref" : "MyValue" },
            { "Ref" : "MyName" },
            "Hello World" ] ]
    }
}

YAML

UserData:
  Fn::Base64: !Sub |
     Ref: MyValue
     Ref: MyName
     Hello World

Base64 encoded UserData property with AccessKey and SecretKey

This example shows the assembly of a UserData property using the Fn::Base64 and Fn::Join functions. It includes the AccessKey and SecretKey information. The references AccessKey and SecretKey are parameters that must be defined in the Parameters section of the template.

JSON

"UserData" : {
    "Fn::Base64" : {
        "Fn::Join" : [ "", [
            "ACCESS_KEY=", { "Ref" : "AccessKey" },
            "SECRET_KEY=", { "Ref" : "SecretKey" } ]
        ]
    }
}

YAML

UserData:
  Fn::Base64: !Sub |
     ACCESS_KEY=${AccessKey}
     SECRET_KEY=${SecretKey}

Parameters section with one literal string parameter

The following example depicts a valid Parameters section declaration in which a single String type parameter is declared.

JSON

"Parameters" : {
    "UserName" : {
        "Type" : "String",
        "Default" : "nonadmin",
        "Description" : "Assume a vanilla user if no command-line spec provided"
    }
}

YAML

Parameters:
  UserName:
    Type: String
    Default: nonadmin
    Description: Assume a vanilla user if no command-line spec provided

Parameters section with string parameter with regular expression constraint

The following example depicts a valid Parameters section declaration in which a single String type parameter is declared. The AdminUserAccount parameter has a default of admin. The parameter value must have a minimum length of 1, a maximum length of 16, and contains alphabetical characters and numbers but must begin with an alphabetical character.

JSON

"Parameters" : {
    "AdminUserAccount": {
      "Default": "admin",
      "NoEcho": "true",
      "Description" : "The admin account user name",
      "Type": "String",
      "MinLength": "1",
      "MaxLength": "16",
      "AllowedPattern" : "[a-zA-Z][a-zA-Z0-9]*"
    }
}

YAML

Parameters:
  AdminUserAccount:
    Default: admin
    NoEcho: true
    Description: The admin account user name
    Type: String
    MinLength: 1
    MaxLength: 16
    AllowedPattern: '[a-zA-Z][a-zA-Z0-9]*'

Parameters section with number parameter with MinValue and MaxValue constraints

The following example depicts a valid Parameters section declaration in which a single Number type parameter is declared. The WebServerPort parameter has a default of 80 and a minimum value 1 and maximum value 65535.

JSON

"Parameters" : {
    "WebServerPort": {
      "Default": "80",
      "Description" : "TCP/IP port for the web server",
      "Type": "Number",
      "MinValue": "1",
      "MaxValue": "65535"
    }
}

YAML

Parameters:
  WebServerPort:
    Default: 80
    Description: TCP/IP port for the web server
    Type: Number
    MinValue: 1
    MaxValue: 65535

Parameters section with number parameter with AllowedValues constraint

The following example depicts a valid Parameters section declaration in which a single Number type parameter is declared. The WebServerPort parameter has a default of 80 and allows only values of 80 and 8888.

JSON

"Parameters" : {
    "WebServerPortLimited": {
      "Default": "80",
      "Description" : "TCP/IP port for the web server",
      "Type": "Number",
      "AllowedValues" : ["80", "8888"]
    }
}

YAML

Parameters:
  WebServerPortLimited:
    Default: 80
    Description: TCP/IP port for the web server
    Type: Number
    AllowedValues:
    - 80
    - 8888

Parameters section with one literal CommaDelimitedList parameter

The following example depicts a valid Parameters section declaration in which a single CommaDelimitedList type parameter is declared. The NoEcho property is set to TRUE, which will mask its value with asterisks (*****) in the describe-stacks output, except for information stored in the locations specified below.

Important

Using the NoEcho attribute does not mask any information stored in the following:

We strongly recommend you do not use these mechanisms to include sensitive information, such as passwords or secrets.

Important

Rather than embedding sensitive information directly in your CloudFormation templates, we recommend you use dynamic parameters in the stack template to reference sensitive information that is stored and managed outside of CloudFormation, such as in the AWS Systems Manager Parameter Store or AWS Secrets Manager.

For more information, see the Do not embed credentials in your templates best practice.

JSON

"Parameters" : {
    "UserRoles" : {
        "Type" : "CommaDelimitedList",
        "Default" : "guest,newhire",
        "NoEcho" : "TRUE"
    }
}

YAML

Parameters:
  UserRoles:
    Type: CommaDelimitedList
    Default: "guest,newhire"
    NoEcho: true

Parameters section with parameter value based on pseudo parameter

The following example shows commands in the EC2 user data that use the pseudo parameters AWS::StackName and AWS::Region. For more information about pseudo parameters, see Pseudo parameters reference.

JSON

          "UserData"       : { "Fn::Base64" : { "Fn::Join" : ["", [
             "#!/bin/bash -xe\n",
             "yum install -y aws-cfn-bootstrap\n",

             "/opt/aws/bin/cfn-init -v ",
             "         --stack ", { "Ref" : "AWS::StackName" },
             "         --resource LaunchConfig ",
             "         --region ", { "Ref" : "AWS::Region" }, "\n",

             "/opt/aws/bin/cfn-signal -e $? ",
             "         --stack ", { "Ref" : "AWS::StackName" },
             "         --resource WebServerGroup ",
             "         --region ", { "Ref" : "AWS::Region" }, "\n"
        ]]}}
      }

YAML

UserData:
  Fn::Base64: !Sub |
     #!/bin/bash -xe
     yum update -y aws-cfn-bootstrap
     /opt/aws/bin/cfn-init -v --stack ${AWS::StackName} --resource LaunchConfig --region ${AWS::Region}
     /opt/aws/bin/cfn-signal -e $? --stack ${AWS::StackName} --resource WebServerGroup --region ${AWS::Region}

Mapping section with three mappings

The following example depicts a valid Mapping section declaration that contains three mappings. The map, when matched with a mapping key of Stop, SlowDown, or Go, provides the RGB values assigned to the corresponding RGBColor attribute.

JSON

"Mappings" : {
    "LightColor" : {
        "Stop" : {
            "Description" : "red",
            "RGBColor" : "RED 255 GREEN 0 BLUE 0"
        },
        "SlowDown" : {
            "Description" : "yellow",
            "RGBColor" : "RED 255 GREEN 255 BLUE 0"
        },
        "Go" : {
            "Description" : "green",
            "RGBColor" : "RED 0 GREEN 128 BLUE 0"
        }
    }
}

YAML

Mappings:
  LightColor:
    Stop:
      Description: red
      RGBColor: "RED 255 GREEN 0 BLUE 0"
    SlowDown:
      Description: yellow
      RGBColor: "RED 255 GREEN 255 BLUE 0"
    Go:
      Description: green
      RGBColor: "RED 0 GREEN 128 BLUE 0"

Description based on literal string

The following example depicts a valid Description section declaration where the value is based on a literal string. This snippet can be for templates, parameters, resources, properties, or outputs.

JSON

"Description" : "Replace this value"

YAML

Description: "Replace this value"

Outputs section with one literal string output

This example shows a output assignment based on a literal string.

JSON

"Outputs" : {
    "MyPhone" : {
        "Value" : "Please call 555-5555",
        "Description" : "A random message for aws cloudformation describe-stacks"
    }
}

YAML

Outputs:
  MyPhone:
    Value: Please call 555-5555
    Description: A random message for aws cloudformation describe-stacks

Outputs section with one resource reference and one pseudo reference output

This example shows an Outputs section with two output assignments. One is based on a resource, and the other is based on a pseudo reference.

JSON


"Outputs" : {
   "SNSTopic" : { "Value" : { "Ref" : "MyNotificationTopic" } },
   "StackName" : { "Value" : { "Ref" : "AWS::StackName" } }
}

YAML

Outputs:
  SNSTopic:
    Value: !Ref MyNotificationTopic
  StackName:
    Value: !Ref AWS::StackName

Outputs section with an output based on a function, a literal string, a reference, and a pseudo parameter

This example shows an Outputs section with one output assignment. The Join function is used to concatenate the value, using a percent sign as the delimiter.

JSON

"Outputs" : {
    "MyOutput" : {
        "Value" : { "Fn::Join" :
            [ "%", [ "A-string", {"Ref" : "AWS::StackName" } ] ]
        }
    }
}

YAML

Outputs:
  MyOutput:
    Value: !Join [ %, [ 'A-string', !Ref 'AWS::StackName' ]]

Template format version

The following snippet depicts a valid AWSTemplateFormatVersion section declaration.

JSON

"AWSTemplateFormatVersion" : "2010-09-09"

YAML

AWSTemplateFormatVersion: '2010-09-09'

AWSTags property

This example shows an AWS Tags property. You would specify this property within the Properties section of a resource. When the resource is created, it will be tagged with the tags you declare.

JSON

"Tags" : [
      {
        "Key" : "keyname1",
        "Value" : "value1"
      },
      {
        "Key" : "keyname2",
        "Value" : "value2"
      }
    ]

YAML

Tags: 
  - 
    Key: "keyname1"
    Value: "value1"
  - 
    Key: "keyname2"
    Value: "value2"