# Removing Stacks

If you ever need to delete a Quilt stack from your AWS account, you should know that:

* Your data in S3 buckets remains accessible.
* You can continue using the Quilt SDK for reading and writing packages.
* Stack-managed resources (Athena tables, Postgres database, audit logs) will be affected.
* The deletion behavior varies between CloudFormation and Terraform deployments.

***

### I. Impact Assessment and Preparation

#### What May Be Deleted

* Custom configurations specific to the Quilt stack (e.g., IAM roles, resource mappings, permissions).
* Analytics data in stack-managed buckets.
* Audit logs and Athena querying setups.
* User account and tabulator configurations.

#### Recommended Actions

* Export analytics data you need to keep.
* Save important audit logs.
* Document existing Athena configurations if you'll need to recreate them.
* Export the Postgres database (containing, e.g., user accounts and tabulator configuration) in case you want to reuse it for future stacks.

***

### II. Stack Deletion Process

#### Using CloudFormation

1. **Start the Deletion Process**
   * Navigate to the **CloudFormation** console in your AWS region.
   * Select your stack under **CloudFormation > Stacks**.
   * Click **Delete Stack** to begin the process.
2. **Empty or Ignore Non-Deleted Resources**
   * CloudFormation attempts to delete all stack-managed resources.
   * If a resource cannot be deleted (e.g., non-empty S3 bucket):
     * It will show a **DELETE\_FAILED** status in the **Events** tab.
     * Failed resources remain intact, including non-empty S3 buckets.
     * Other independent resources will still be deleted.
     * The stack enters the **DELETE\_FAILED** state.
   * If you wish to remove those resources:
     * Back up any important files.
     * Remove all files from the bucket via the S3 console or CLI.
     * Retry the deletion process.
   * Alternatively, you can leave them undeleted, though that may require manual cleanup later.

#### Using Terraform

1. **Start the Deletion Process**
   * Open a terminal in your Terraform configuration directory.
   * Run `terraform destroy`.
2. **Empty or Retain Non-Deleted Resources**
   * Terraform stops at the first resource it cannot delete (e.g., non-empty S3 buckets created by CloudFormation).
   * Dependencies of the failed resource are preserved.
   * To resolve, back up important files and clear the bucket contents.
   * Once addressed, resume deletion by re-running `terraform destroy`.

***

### III. Final Steps

* Verify deletion of all non-retained resources.
* Confirm that the stack is no longer listed in CloudFormation or Terraform.
* Check for any orphaned resources or residual costs using the **AWS Cost Explorer**.

***

### IV. After Stack Deletion

* Your S3 bucket data remains intact and accessible.
* The Quilt SDK continues to function for package operations.
* Recreate any necessary Athena/Glue configurations if needed.


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