How to do it...

1. Create a new Packer template file, and start by defining an amazon-ebs builder in the builders section:

      "builders": [ 
        { 
          "type": "amazon-ebs", 
          "instance_type": "t2.micro", 
          "region": "us-east-1", 
          "source_ami": "ami-9be6f38c", 
          "ssh_username": "ec2-user", 
          "ami_name": "aws-linux-apache {{timestamp}}" 
        } 
      ],

The entire template file must be a valid JSON object. Remember to enclose the sections in curly braces: { ... }.

2. Create a provisioners section, and include the following snippet to install and activate Apache:

      "provisioners": [ 
        { 
          "type": "shell", 
          "inline": [ 
            "sudo yum install -y httpd", 
            "sudo chkconfig httpd on" 
          ] 
        } 
      ]

3. Save the file with a specific name, such as 04-creating-machine-images.json.

4. Validate the configuration file you've created with the following packer validate command:

      packer validate 04-creating-machine-images.json

5. When valid, build the AMI with the following command:

      packer build 04-creating-machine-images.json

6. Wait until the process is complete. While it is running, you will see an output similar to the following:

7. Take note of the AMI ID returned by Packer so that you can use it when launching instances in the future: