Update your stack template - AWS CloudFormation (original) (raw)

To modify the resources or properties in a CloudFormation stack, you must update the stack's template. Start with the existing template for that stack and make your changes to it. If you have the template stored in a source control system, use a copy of that as your starting point. Otherwise, you can get a copy of the template from CloudFormation.

If you only want to change the parameters or settings of the stack (like a stack's Amazon SNS topic), you can reuse the existing template without getting a copy.

You can update a CloudFormation stack template by using a text editor or Infrastructure Composer.

To update an existing stack template by using Infrastructure Composer

1. Sign in to the AWS Management Console and open the AWS CloudFormation console athttps://console.aws.amazon.com/cloudformation.
2. On the Stacks page, choose the name of the stack to update.
3. Choose the Template tab, and then choose View in Infrastructure Composer.
   CloudFormation opens the template in Infrastructure Composer.
4. Update your template using one of the following methods:
   • Canvas interface: Here, you can drag and drop from theResources pallete. Configure resources by double-clicking on a card to open the Resource properties panel. Connect resources as needed. For detailed instructions on using theCanvas interface, see How to compose in AWS Infrastructure Composer.
   • Template interface: Switch from theCanvas to the Template interface. Make in-line updates to the template code. Toggle between JSON to YAML formats as needed.
5. Choose Validate to check for any syntax errors in the template.
6. When you are ready to export changes to CloudFormation, choose Update template.

To update an existing stack template by using the AWS CLI

1. To get the template for the stack you want to update, use the get-template CLI command.
2. Copy the template, paste it into a text file, modify it, and save it. Copy_only_ the template. The command encloses the template in quotation marks, but don't copy the quotation marks surrounding the template. The template itself starts with an open brace and ends with the final close brace. Specify changes to the stack's resources in this file.

Keep in mind the following points as you make changes to your template:

• You can't add, modify, or delete a parameter that's used by a resource that doesn't support updates.
• For most resources, changing the logical name of a resource is equivalent to deleting that resource and replacing it with a new one. Any other resources that depend on the renamed resource also need to be updated and might cause them to be replaced. Other resources require you to update a property (not just the logical name) in order to initiate an update.
• Some resources may have constraints about what values you can set for certain properties. For example, changes to the AllocatedStorage property for an RDS database instance must be greater than the current value. If your update violates these rules, that part will fail.
• Updating one resource can also affect others that reference it. If you use functions like Ref or GetAtt to set a property based on another resource, CloudFormation will update the referencing resource too when the referenced one changes.
• For information about the effects of updating particular resource properties, see theAWS Resource Types Reference. For each property, the effects of an update will be one of the following:
  • Update requires: No interruption
  • Update requires: Some interruptions
  • Update requires: Replacement
• You can verify the JSON or YAML syntax of your template by using the validate-template CLI command or by specifying your template on the console. The console performs validation automatically. However, these methods only verify the syntax of your template and don't validate the property values that you specified for a resource are valid for that resource. For more complex validations or to check for best practices, you might also use additional tools like CloudFormation Linter (cfn-lint) and CloudFormation Rain (rain fmt).

Note

Sometimes CloudFormation won't allow certain changes you try to make, and it will tell you the change isn't permitted. This message might occur asynchronously, however, because resources are created and updated by CloudFormation in a non-deterministic order by default.