To launch an EC2 instance, we first need an AMI to launch the image from. Although it is possible to create your own customized AMI from scratch, this is an advanced topic that we will leave for Chapter 6. In the meantime we will take advantage of preexisting images that are available to the public and use one of these as a starting point. We will use a public image provided by Amazon specifically for the purpose of experimenting with the EC2 service. The AMI we will use goes by the catchy name of ec2-public-images/getting-started.manifest.xml.
To be completely accurate, the AMI is not really named like this; the unwieldy title above is actually the location of the manifest file in S3 that describes the image. In the API operations available in EC2 for managing images, the manifest file name is the closest thing to a long-term name for an AMI; it is therefore the most convenient way to refer to this image.
To start an AMI instance, we need to know the identifier value assigned to the AMI in EC2. The identifier we need is distinct from the location of the AMI’s manifest, and it can potentially change over time if the AMI file is updated or reregistered. In fact, the ID value for this AMI may well be different by the time you read this book. To launch an instance from an AMI, we must first look up its identifier value.
The DescribeImages operation shown in Table 5-8 lists the AMIs available to you in the EC2 environment. The AMIs available ...