Amazon Machine Image

Introduction

In Amazon EC2 (Elastic Compute Cloud), an Amazon Machine Image (AMI) is a pre-configured virtual machine image, which includes the necessary information to launch an instance, such as the operating system, application server, and applications. AMIs provide a convenient way to create instances with specific configurations, software, and settings. Here are key points about AMIs in EC2:

1. AMI Components:

   • Root Volume: The root volume contains the operating system, and it serves as the base for the instance.

   • Block Device Mapping: AMIs can include additional volumes and block device mapping information for data storage.

2. Public and Private AMIs:

   • Public AMIs: AWS provides a repository of publicly available AMIs that users can use as a starting point for their instances. These AMIs are shared by the AWS community.

   • Private AMIs: Users can also create their own custom AMIs and keep them private, limiting access to specified AWS accounts.

3. AMI Creation:

   • Bundle and Upload: Users can create custom AMIs by bundling the root file system and additional volumes, and then uploading the bundled image to Amazon S3.

   • Instance Creation: Alternatively, users can create an instance, customize it, and then create an AMI from that instance.

4. Instance Launch:

   • AMI Selection: When launching an EC2 instance, users choose an AMI to use as the base for the instance.

   • Instance Configuration: Users can specify the instance type, key pair, security groups, and other configuration settings during launch.

5. AMI Types:

   • Amazon Linux AMIs: Optimized and maintained by AWS, Amazon Linux AMIs provide a lightweight and secure Linux environment.

   • Windows AMIs: Include various editions of Windows Server, providing flexibility for Windows-based workloads.

   • Custom AMIs: Users can create custom AMIs based on their specific requirements and configurations.

6. Updating and Versioning:

   • AMI Updates: Over time, users may need to update their AMIs to include security patches, software updates, or new configurations.

   • AMI Versioning: Users can create new versions of AMIs to track changes and improvements.

7. Snapshot Dependency:

   • EBS Snapshots: The root volume of an instance is often an Amazon Elastic Block Store (EBS) volume. When creating an AMI, a snapshot of the root volume is typically taken, and the AMI references that snapshot.

8. Sharing AMIs:

   • AMI Sharing: Users can share custom AMIs with other AWS accounts, making it possible for others to use those images.