How to config a instance using run_instance of aws-sdk-ec2/client.rb?

Question

I hope you are all well.

I want to create an instance for a cluster using ruby.

First, I created the client:

client = Aws::ECS::Client.new(Client.params)

After that, I tried to prepare a variable for the user_data field:

user_data = message = Base64.encode64("#!/bin/bash\necho ECS_CLUSTER=test >> /etc/ecs/ecs.config\n")

And last, but not least, I tried to create the instance using the run_instances method:

client.run_instances({
  image_id: '<image-id>',
  instance_type: '<instance-type>',
  key_name: '<key-name>',
  max_count: 1,
  min_count: 1,
  user_data: user_data,
  monitoring: { enabled: false },
  security_group_ids: ['<security-group-ids>'],
  iam_instance_profile: {
    name: '<iam-instance-profile>'
  }
})

The instance is created, but the contents of the ecs.config file are empty. I'm not sure what I'm doing wrong.

I was hoping that the file would have ECS_CLUSTER=test inside.

Can anyone give me a hint of how to solve this, please?

Thank you!