Your team uses a CloudFormation template to launch AWS resources for an application.
The following script is used in the template to initialize files and install packages in EC2 instances: UserData: Fn::Base64: !Sub | #!/bin/bash -xe yum update -y aws-cfn-bootstrap /opt/aws/bin/cfn-init -v --stack ${AWS::StackName} --resource LaunchConfig --configsets packages_install -- region us-east-1 The CloudFormation template works well in the us-east-1 region.
However, when you try to use the same template in the us-west-1 region, the cfn-init helper script reports an error.
How would you modify the script so that the CloudFormation template is portable and can be used in different AWS regions?
Click on the arrows to vote for the correct answer
A. B. C. D.Correct Answer: B.
Option A is incorrect because the region option cannot be “us-east-1/us-west-1”
The option must be the CloudFormation regional endpoint according to https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-init.html.
Option B is CORRECT because ${AWS::Region} is a pseudo parameter that AWS CloudFormation predefines.
The parameter returns the correct region name so that the script works no matter which region it runs.
Option C is incorrect because in the cfn-init helper script, “*” is not allowed for the region option.
Option D is incorrect because "Region" is not a parameter predefined by CloudFormation.
The pseudo parameter “${AWS::Region}” is predefined.
References:
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-sub.html, https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-init.htmlThe cfn-init helper script is used to initialize files and install packages on EC2 instances launched by a CloudFormation template. In this case, the script is failing when the same template is used in the us-west-1 region, indicating that the region parameter in the script needs to be modified to make the template portable across different regions.
Option A suggests modifying the cfn-init helper script by adding both us-east-1 and us-west-1 to the region parameter. While this may work, it is not the best approach since it requires manually updating the script each time a new region is added.
Option B is the correct answer as it provides a more scalable solution. It modifies the cfn-init helper script to use the AWS::Region pseudo parameter, which dynamically resolves to the region in which the CloudFormation stack is launched. This ensures that the script can be used in any region without manual modification.
Option C suggests using a wildcard character to indicate that the script should be executed in all regions. This is not recommended as it can result in unintended consequences and security risks.
Option D suggests using a parameter to reference the region. While this is a valid approach, it requires additional configuration of the parameter and may not be as straightforward as using the AWS::Region pseudo parameter.
In conclusion, the best approach to make the CloudFormation template portable across different AWS regions is to modify the cfn-init helper script to use the AWS::Region pseudo parameter, as suggested in option B.