packer-cn/website/source/partials/builder/amazon/common/_BlockDevice.html.md

These will be attached when booting a new instance from your AMI. Your options here may vary depending on the type of VM you use. Example:

"builders":[{
"type":"...",
"ami_block_device_mappings":[{
          "device_name":"xvda",
          "delete_on_termination":true,
          "volume_type":"gp2"
    }]
 }

Documentation for Block Devices Mappings can be found here: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/block-device-mapping-concepts.html