区分 Shell 变量和 Cloudformation 模板参数

Question

I have come across a usecase where i am seeing conflict between Shell Variables and Cloudformation Parameters .

Example:

I am writing AWS::ImageBuilder::Component

Parameters:
  cloudVersion:
    Type: String
    Default: "1.10.11"
    Description: Cloud Version to release
Resources:
  CloudInstallComponent:
    Type: AWS::ImageBuilder::Component
    Properties:
      Name: CloudAMI
      Version: !Ref cloudVersion
      Description: Install the latest cloud.
      ChangeDescription: Cloud First version
      Platform: Linux
      Data: !Sub |
        name: DeployCloudComponents
        description: This is to deploy cloud components.
        schemaVersion: 1.0
        phases:
          - name: build
            steps:
              - name: CreateUser
                action: ExecuteBash
                inputs:
                  commands:
                    - "Creating New User cloud"
                    - export GroupID=7560
                    - export UserID=7560
                    - export USER=cloud
                    - sudo groupadd --gid ${GroupID} ${USER}
                    - sudo useradd --uid ${UserID} --gid ${GroupID} --create-home --shell /bin/bash ${USER}
                    - sudo usermod -G wheel ${USER}
                    - |-
                        echo "${USER}    ALL=(ALL)       NOPASSWD: ALL" >> /etc/sudoers
                    - sudo wget -O a.tgz 'abc.net/mg/api/v1/help/${cloudVersion}/on/download/a.tgz'

Now in above code snippet GroupID , UserID and USER are shell variables while cloudVersion is cloudformation parameter.

Question is how to differentiate between them?

I am seeing errors in cfn-linter like below

Error   Cfn-Lint    Parameter GroupID for Fn::Sub not found at Resources/CloudInstallComponent/Properties/Data/Fn::Sub  160:7
Error   Cfn-Lint    Parameter USER for Fn::Sub not found at Resources/K2CloudInstallComponent/Properties/Data/Fn::Sub   160:7
Error   Cfn-Lint    Parameter UserID for Fn::Sub not found at Resources/K2CloudInstallComponent/Properties/Data/Fn::Sub 160:7

I can solve the ambiguity by taking three shell variables as cloudformation parameters.

But if anyone can suggest an existing way to differentiate between both kind of variables would be good.

Thanks in advance.

Answer 1

You have to escape your variables using ${!} notation:

Parameters:
  cloudVersion:
    Type: String
    Default: "1.10.11"
    Description: Cloud Version to release
Resources:
  CloudInstallComponent:
    Type: AWS::ImageBuilder::Component
    Properties:
      Name: CloudAMI
      Version: !Ref cloudVersion
      Description: Install the latest cloud.
      ChangeDescription: Cloud First version
      Platform: Linux
      Data: !Sub |
        name: DeployCloudComponents
        description: This is to deploy cloud components.
        schemaVersion: 1.0
        phases:
          - name: build
            steps:
              - name: CreateUser
                action: ExecuteBash
                inputs:
                  commands:
                    - "Creating New User cloud"
                    - export GroupID=7560
                    - export UserID=7560
                    - export USER=cloud
                    - sudo groupadd --gid ${!GroupID} ${!USER}
                    - sudo useradd --uid ${!UserID} --gid ${!GroupID} --create-home --shell /bin/bash ${!USER}
                    - sudo usermod -G wheel ${!USER}
                    - |-
                        echo "${!USER}    ALL=(ALL)       NOPASSWD: ALL" >> /etc/sudoers
                    - sudo wget -O a.tgz 'abc.net/mg/api/v1/help/${cloudVersion}/on/download/a.tgz'