Windows EC2 User data script not working as expected

Question

I'm trying to detach an EBS volume from an EC2 instance and attach it to a new EC2 instance which I'm starting up using a CloudFormation template(YAML). Below is the UserData section. I use a timeout command to give time for the EBS volume to properly detach. yet this script does not attach the volume to the instance properly at start up.

UserData: !Base64
        <script>
        aws ec2 detach-volume --instance-id i-05e13cbyrr78f75f7 --volume-id vol-0e5a92637c3dec929x --region us-east-1
        timeout /t 100
        for /F %%L in ('powershell Invoke-RestMethod -Uri 'http://169.254.169.254/latest/meta-data/instance-id'') do (set "ID=%%L")
        aws ec2 attach-volume --volume-id vol-0e5a92637c3dec929x --instance-id %ID% --device xvdf --region us-east-1
        </script>

But when I run the same script as a batch file after the instance is up and running, it works fine. What am I missing here? The UserdataExecution.log indicates,

2023/04/28 07:05:43Z: <script> tag was provided.. running script content
2023/04/28 07:06:14Z: Message: The errors from user data script: usage: 
Note: AWS CLI version 2, the latest major version of the AWS CLI, is now stable and recommended for general use. For more information, see the AWS CLI version 2 installation instructions at: https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html

usage: aws [options] <command> <subcommand> [<subcommand> ...] [parameters]
To see help text, you can run:

  aws help
  aws <command> help
  aws <command> <subcommand> help
aws: error: argument --instance-id: expected one argument

2023/04/28 07:06:14Z: Message: The output from user data script: 
C:\Windows\system32>aws ec2 detach-volume --instance-id i-05e13cbyrr78f75f7 --volume-id vol-0e5a92637c3dec929x --region us-east-1 timeout /t 100 for /F %L in ('powershell Invoke-RestMethod -Uri 'http://169.254.169.254/latest/meta-data/instance-id'') do (set "ID=%L") aws ec2 attach-volume --volume-id vol-0e5a92637c3dec929x --instance-id  --device xvdf --region us-east-1  

2023/04/28 07:06:14Z: User data script completed.

Can you try it like this? [AWS CloudFormation UserData Example · GitHub](https://gist.github.com/jeffbrl/abfd84d8d8586495632ba9b8489322e2) and [Trying to understand Cloudformation syntax for UserData script](https://serverfault.com/a/1111263/267968)? — John Rotenstein, Apr 28 '23 at 12:30
UserData: Fn::Base64: !Sub | This formatting worked and it does give the expected results. @JohnRotenstein — isuranger, May 03 '23 at 12:34

score 0 · Accepted Answer · answered May 03 '23 at 21:25

Here are some examples of passing User Data via YAML. Note that they use !Sub | that might fix things for you:

From AWS CloudFormation UserData Example · GitHub:

UserData:
  Fn::Base64:
    !Sub |
      #!/bin/bash -xe
      yum update -y aws-cfn-bootstrap
      /opt/aws/bin/cfn-init -v --stack ${AWS::StackName} --resource LaunchConfig --configsets wordpress_install --region ${AWS::Region}
      /opt/aws/bin/cfn-signal -e $? --stack ${AWS::StackName} --resource WebServerGroup --region ${AWS::Region}

From amazon web services - Trying to understand Cloudformation syntax for UserData script - Server Fault:

UserData:
    Fn::Base64: !Sub |
      #!/bin/bash -xe
      # Pre-Bootstrap Configuration
      yum update -y
      yum install -y aws-cfn-bootstrap git docker
      usermod -a -G docker ec2-user
      systemctl enable docker
      systemctl start docker
      curl -L https://github.com/docker/compose/releases/latest/download/docker-compose-$(uname -s)-$(uname -m) -o /usr/bin/docker-compose
      chmod +x /usr/bin/docker-compose

Windows EC2 User data script not working as expected

1 Answers1