create folder inside S3 bucket using Cloudformation

Question

I'm able to create an S3 bucket using cloudformation but would like to create a folder inside an S3 bucket..like

<mybucket>--><myfolder> 

Please let me know the template to be used to create a folder inside a bucket ...both should be created at the sametime...

I'm Using AWS lambda as below

stackname = 'myStack' client = boto3.client('cloudformation') response = client.create_stack(     StackName= (stackname),     TemplateURL= 'https://s3.amazonaws.com/<myS3bucket>/<myfolder>/nestedstack.json',     Parameters=<params> ) 

Answer 1

AWS doesn't provide an official CloudFormation resource to create objects within an S3 bucket. However, you can create a Lambda-backed Custom Resource to perform this function using the AWS SDK, and in fact the gilt/cloudformation-helpers GitHub repository provides an off-the-shelf custom resource that does just this.

As with any Custom Resource setup is a bit verbose, since you need to first deploy the Lambda function and IAM permissions, then reference it as a custom resource in your stack template.

First, add the Lambda::Function and associated IAM::Role resources to your stack template:

"S3PutObjectFunctionRole": {   "Type": "AWS::IAM::Role",   "Properties": {     "AssumeRolePolicyDocument": {       "Version" : "2012-10-17",       "Statement": [         {           "Effect": "Allow",           "Principal": {             "Service": [ "lambda.amazonaws.com" ]           },           "Action": [ "sts:AssumeRole" ]         }       ]     },     "ManagedPolicyArns": [       { "Ref": "RoleBasePolicy" }     ],     "Policies": [       {         "PolicyName": "S3Writer",         "PolicyDocument": {           "Version" : "2012-10-17",           "Statement": [             {               "Effect": "Allow",               "Action": [                 "s3:DeleteObject",                 "s3:ListBucket",                 "s3:PutObject"               ],               "Resource": "*"             }           ]         }       }     ]   } }, "S3PutObjectFunction": {   "Type": "AWS::Lambda::Function",   "Properties": {     "Code": {       "S3Bucket": "com.gilt.public.backoffice",       "S3Key": "lambda_functions/cloudformation-helpers.zip"     },     "Description": "Used to put objects into S3.",     "Handler": "aws/s3.putObject",     "Role": {"Fn::GetAtt" : [ "S3PutObjectFunctionRole", "Arn" ] },     "Runtime": "nodejs",     "Timeout": 30   },   "DependsOn": [     "S3PutObjectFunctionRole"   ] }, 

Then you can use the Lambda function as a Custom Resource to create your S3 object:

"MyFolder": {   "Type": "Custom::S3PutObject",   "Properties": {     "ServiceToken": { "Fn::GetAtt" : ["S3PutObjectFunction", "Arn"] },     "Bucket": "mybucket",     "Key": "myfolder/"   } }, 

You can also use the same Custom Resource to write a string-based S3 object by adding a Body parameter in addition to Bucket and Key (see the docs).