Where does packer store the private key?

Question

From ubuntu shell I ran below command, to talk to aws platform, to customise amazon ami(ami-9abea4fb):

$ packer build -debug template.packer 
Debug mode enabled. Builds will not be parallelized.
amazon-ebs output will be in this color.

==> amazon-ebs: Prevalidating AMI Name...
==> amazon-ebs: Pausing after run of step 'StepPreValidate'. Press enter to continue. 
==> amazon-ebs: Inspecting the source AMI...
==> amazon-ebs: Pausing after run of step 'StepSourceAMIInfo'. Press enter to continue. 
==> amazon-ebs: Creating temporary keypair: packer 5dfe9f3b-9cc2-cbfa-7349-5c8ef50c64d5
    amazon-ebs: Saving key for debug purposes: ec2_amazon-ebs.pem
==> amazon-ebs: Pausing after run of step 'StepKeyPair'. Press enter to continue. 

where template.packer is:

{
    "builders": [
        {
            "type": "amazon-ebs",
            "region": "us-west-2",
            "source_ami": "ami-9abea4fb",
            "instance_type": "t2.micro",
            "ssh_username": "ubuntu",
            "ami_name": "MiddleTier-{{isotime | clean_ami_name}}",
            "ami_description": "Amazon AMI customised",
            "tags": {
                "role": "MiddleTier"
            },
            "run_tags":{
                "role": "buildSystem"
            }
        }
    ],
    "provisioners": [

    ],
    "post-processors":[

    ]
}

and my understanding is, AWS has created a private key(ec2_amazon-ebs.pem) for packer to talk to EC2 instance in passwordless way, as mentioned in above steps.

But I do not see packer copying the private key(ec2_amazon-ebs.pem) in my laptop(as ~/.ssh/ec2_amazon-ebs.pem)

How does packer talk to EC2? without copying as ~/.ssh/ec2_amazon-ebs.pem in my laptop

Answer 1

Unless Packer is given a private SSH with the ssh_private_key_file Packer creates an ephemeral that is only kept in memory while Packer is running.

When you run with the -debug flag this ephemeral key is saved into the current working directory. This is to enable you to troubleshoot the build by manually SSH'ing into the instance.