A configuration files for creating a lightly modified AMI for ubuntu 12.04LTS

packer_example.sh

# to get my credentials in place --> to create env vars with my key/secret
source ~/ry_aws.sh

packer build \
    -var aws_access_key=$AWS_ACCESS_KEY \
    -var aws_secret_key=$AWS_SECRET_KEY \
    packer_example_aws.json

packer_example_aws.json

{
  "variables": {
    "aws_access_key": "",
    "aws_secret_key": ""
  },
  "builders": [{
    "type": "amazon-ebs",
    "access_key": "{{user `aws_access_key`}}",
    "secret_key": "{{user `aws_secret_key`}}",
    "region": "us-east-1",
    "source_ami": "ami-de0d9eb7",
    "instance_type": "t1.micro",
    "ssh_username": "ubuntu",
    "ami_name": "packer-example {{timestamp}}"
  }],
  "provisioners": [{
    "type": "shell",
    "inline": [
      "sleep 30",
      "sudo apt-get update",
      "sudo apt-get install -y redis-server"
    ]
  }]
}