"Please specify a stack name using --stack or persist it in samconfig.toml" when deploying with Serverless Framework

Question

I’m using the Serverless Framework (sls) to deploy an AWS Lambda function. When I run:

sls deploy --stage dev

I get this error:

✖ Error: Please specify a stack name using the --stack option, or persist it in the samconfig.toml file.

Context:

• My serverless.yml already includes the service field:

  service: py-events
  provider:
    name: aws
  

• This worked previously but suddenly started failing.
• I’m not explicitly using AWS SAM, but my project has a template.yaml file.

Debug Logs:
The error traces to getCfnConfig in the Serverless Framework, with the MISSING_STACK_NAME code.

Question:
How do I resolve this stack name error, and why did it suddenly appear despite having a service defined?

What I’ve tried:

• Adding stage: dev to provider in serverless.yml.
• Specifying --stack my-stack-dev in the CLI.

Answer 1

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Answer

This error occurs when the Serverless Framework (or an integrated tool like AWS SAM) cannot resolve a CloudFormation stack name. Here’s how to fix it:

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1. Ensure service and stage Are Properly Configured

Add stage under the provider in serverless.yml. The stack name is auto-generated as ${service}-${stage}:

service: py-events
provider:
  name: aws
  stage: dev  # 👈 Required for stack name resolution
  region: us-east-1  # Optional but recommended

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2. Explicitly Define the Stack Name (Optional)

Override the default stack name in serverless.yml:

provider:
  name: aws
  stackName: py-events-${sls:stage}  # e.g., "py-events-dev"

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3. Remove Conflicting SAM Files (If Not Using SAM)

If you’re not using AWS SAM:

• Delete template.yaml (SAM’s config file).
• Remove samconfig.toml (if present).

The Serverless Framework will then use its own stack naming logic.

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4. If Using AWS SAM

If you are using SAM (e.g., for other resources):

1. Create/update samconfig.toml in your project root:

   version = 0.1
   [default.deploy.parameters]
   stack_name = "py-events-dev"
   region = "us-east-1"
   

2. Deploy with SAM instead of sls:

   sam deploy --config-file samconfig.toml
   

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Why Did This Happen Suddenly?

• SAM Integration Conflict: If a template.yaml or samconfig.toml file was added recently, the Serverless Framework may default to SAM’s deployment logic, which requires explicit stack names.
• AWS SDK/CLI Update: A recent update might have changed how SAM and Serverless Framework interact.

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Final Fix (Serverless Framework Only)

1. Ensure serverless.yml has service, stage, and region:

   service: py-events
   provider:
     name: aws
     stage: dev
     region: us-east-1
   

2. Remove SAM-related files (template.yaml, samconfig.toml).
3. Deploy:

   sls deploy --stage dev
   

This resolves the stack name ambiguity by forcing the Serverless Framework to use its internal naming convention.

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Verify the Fix

After applying the solution, check the AWS CloudFormation console for a stack.

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References:

• Serverless Framework Stack Configuration
• AWS SAM Configuration

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