AWS CloudFormation where will UserData be stored?

Question

if I have a AWS CloudFormation template using UserData block containing script block to be executed, for example:

"UserData": {
    "Fn::Base64": {
        "Fn::Join": [
            "",
            [
                "#!/bin/bash\n",
                "apt-get update\n",
                "apt-get -y upgrade\n",
            ]
        ]
    }
}

After the instance is created,

1. I assume that this script block will be saved somewhere to be execute?
2. If so, where can I find this script on the EC2 instance?
3. Will AWS remove this temporary script after stack is created successfully?

I could not find they mention in the doc.

Thanks

Answer 1

The user-data for an instance is available for any process on the instance to retrieve at this location:

http://169.254.169.254/latest/user-data

The DNS name "instance-data" resolves to that IP address, so if you trust DNS to be up, you can also use the easier to remember:

http://instance-data/latest/user-data

Here are the Amazon docs:

http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AESDG-chapter-instancedata.html