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CloudFormation Troubleshooting

This tutorial shows you how to use AWS CloudShell to run a helper script (list-cfn-events.sh) that gathers and displays all CloudFormation events. This will show you how to quickly zero in on the resource and error message responsible for a deployment failure.

Open AWS CloudShell​

  • Sign in to the AWS Management Console.

  • Click the CloudShell icon in the top navigation bar (looks like a “>_” prompt).

Open CloudShell

Download the Script​

In CloudShell’s terminal, download the pre-built script:

curl -O https://docs.formkiq.com/scripts/list-cfn-events.sh
chmod +x list-cfn-events.sh
note

The chmod +x command sets the script’s execute permission bit, making it executable so you can run it directly with ./list-cfn-events.sh.

Run the Script​

Execute the script, passing your root stack’s name and saving the output into a file:

./list-cfn-events.sh my-root-stack-name > output

You’ll see output like:

========================================
  CloudFormation Events for Stack:
      my-root-stack-name
    (since 2025-06-14T14:30:22Z to now)
========================================

2025-06-14T15:02:10Z    MyBucket        CREATE_COMPLETE    AWS::S3::Bucket        -
2025-06-14T15:01:58Z    MyBucketPolicy  CREATE_FAILED      AWS::S3::BucketPolicy  Policy already exists
…

The script then repeats the header-and-events block for each nested stack.

The output file can be downloaded by selecting Download File under the Actions menu.

Download Output File

Interpret the Results​

  • Look for *_FAILED statusesAny line where the Status column ends in _FAILED indicates the resource that caused the rollback or failure.

  • Read the Status ReasonThe final column often contains the AWS-reported error message (e.g. “Policy already exists”, “Access denied”, etc.).

  • Nested Stack ContextIf the failure occurs inside a nested stack, you’ll see it under that nested stack’s header—so you know exactly which template and resource need fixing.