Run the following to build image.
packer build -var 'aws_access_key=<AWS-access-key>' -var 'aws_secret_key=<AWS-secret-key>' -var 'ami_name=<AMI-name>' -var 'account_name=<account-name>' build.json
aws_access_key is the AWS Access Key Id used for programmatic (API) access to AWS services.
aws_secret_key is the AWS Secret Key Id used for programmatic (API) access to AWS services.
ami_name is the name of AMI.
account_name (Optional) is the user name used in script for locking unnecessary account and adding a custom new user.