cfn-init specify custom json - amazon-web-services

Question

Is there a way to tell cfn-init to use a custom JSON file loaded from disk? That way I can quickly troubleshoot problems, otherwise the only way to change the AWS::CloudFormation::Init section is to delete the stack and create it anew.
I'd rather just make changes to my template.json, then tell something like cfn-init -f C:\template.json ... so it uses C:\template.json instead of getting the template from 169.254.169.254 or however it gets it.

Answer 1

Turns out cfn-init does accept a file, but the file needs to have the "Metadata" key as the root key.
So if we save this to template.json:
{
"AWS::CloudFormation::Init": {
"config": {
"files": {
"C:\\Users\\Administrator\\Desktop\\test-file": {
"source": "https://s3.us-east-2.amazonaws.com/example-bucket/example-file"
}
}
}
},
"AWS::CloudFormation::Authentication": {
"S3AccessCreds": {
"type": "S3",
"buckets": ["example-bucket"],
"roleName": "s3access"
}
}
}
Then we can execute cfn-init -v --region us-east-2 template.json.
Note: Do not include the stack or resource, if you use cfn-init -v -s my_stack -r my_instance --region us-east-2 template.json you will get:
Error: You cannot specify more than one input source for metadata
If you put the entire template file instead of just "Metadata" as root, you will get:
Could not find 'AWS::CloudFormation::Init' key in template.json