Updating stacks using change sets

When you need to update a stack, understanding how your changes will affect running resources before you implement them can help you update stacks with confidence. Change sets allow you to preview how proposed changes to a stack might impact your running resources, including the impact on resource properties and attributes. Whether your changes will delete or replace any critical resources, AWS CloudFormation makes the changes to your stack only when you decide to execute the change set, allowing you to decide whether to proceed with your proposed changes or explore other changes by creating another change set. You can create and manage change sets using the CloudFormation console, AWS CLI, or CloudFormation API.

Topics

• Creating a change set
• Viewing a change set
• Executing a change set
• Deleting a change set
• Example change sets

Important

Change sets don't indicate whether CloudFormation will successfully update a stack. For example, a change set doesn't check if you will surpass an account limit, if you're updating a resource that doesn't support updates, or if you have insufficient permissions to modify a resource, all of which can cause a stack update to fail. If an update fails, CloudFormation attempts to roll back your resources to their original state.

Change Set Overview

The following diagram summarizes how you use change sets to update a stack:

1. Create a change set by submitting changes for the stack that you want to update. You can submit a modified stack template or modified input parameter values. CloudFormation compares your stack with the changes that you submitted to generate the change set; it doesn't make changes to your stack at this point.

2. View the change set to see which stack settings and resources will change. For example, you can see which resources CloudFormation will add, modify, or delete. Additionally, you can see a before-and-after comparison of the resource properties and attributes, such as tags, that CloudFormation will modify.

3. Optional: If you want to consider other changes before you decide which changes to make, create additional change sets. Creating multiple change sets helps you understand and evaluate how different changes will affect your resources and properties. You can create as many change sets as you need.

4. Execute the change set that contains the changes that you want to apply to your stack. CloudFormation updates your stack with those changes.

   Note

   After you execute a change, CloudFormation removes all change sets that are associated with the stack because they aren't applicable to the updated stack.

You can also delete change sets to prevent executing a change set that shouldn't be applied.