User data with !FindInMap [RegionMap, !Ref "AWS::Region", URL]

Question

Hello,

I'm trying to refer to a URL based on the Region map, but I'm not sure what I'm doing wrong here. I want to refer the URL parameter from the region map into the user data. This is under a launch template. Can anyone please guide of what's the correct syntax to do this?

```
    ap-southeast-2:
      AMI: "ami-12134"
      URL: "https://aws-codedeploy-ap-southeast-2.s3.amazonaws.com/latest/install"
```

```
        UserData:
          'Fn::Base64': >
            #!/bin/bash

# SSM

cd /tmp

apt-get update -y

wget
            https://s3.amazonaws.com/ec2-downloads-windows/SSMAgent/latest/debian_amd64/amazon-ssm-agent.deb

dpkg -i amazon-ssm-agent.deb

# Codedploy

apt-get install ruby2.0 -y

curl -O {URL}
            - URL: !FindInMap [RegionMap, !Ref "AWS::Region", URL]

chmod +x ./install

./install auto

apt install uuid -y
```

Steve Kinsman · Answer

The snippets you've provided are a bit small and lacking context so I'm making some guesses here.

Your first snippet is part of a mapping called RegionMap, right?

You need the !FindInMap to resolve while CloudFormation is executing.  Right now it's just treated as plain text in your UserData.  So do something like:

```
UserData:
  Fn::Base64: !Sub
    - |
           #!/bin/bash
           ...
           curl -O ${UrlSubParam}
           ...
    - UrlSubParam: !FindInMap [RegionMap, !Ref "AWS::Region", URL]
```

User data with !FindInMap [RegionMap, !Ref "AWS::Region", URL]

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