func fetchRootDeviceName(ami string, conn *ec2.EC2) (aws.StringValue, error) {
if ami == "" {
return nil, fmt.Errorf("Cannot fetch root device name for blank AMI ID.")
}
log.Printf("[DEBUG] Describing AMI %q to get root block device name", ami)
req := &ec2.DescribeImagesRequest{ImageIDs: []string{ami}}
if res, err := conn.DescribeImages(req); err == nil {
if len(res.Images) == 1 {
return res.Images[0].RootDeviceName, nil
} else {
return nil, fmt.Errorf("Expected 1 AMI for ID: %s, got: %#v", ami, res.Images)
}
} else {
return nil, err
}
}
