amazon-ec2yamlaws-cloudformationamazon-ebsec2-userdata

Windows EC2 User data script not working as expected


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.

Solution

  • 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