Amazon Machine Image
An Amazon Machine Image (AMI) is a special type of virtual appliance that is used to instantiate (create) a virtual machine within the Amazon Elastic Compute Cloud ("EC2"). It serves as the basic unit of deployment for services delivered using EC2.
Like all virtual appliances, the main component of an AMI is a read-only filesystem image which includes an operating system (e.g., Linux, Unix, or Windows) and any additional software required to deliver a service or a portion of it.
The AMI filesystem is compressed, encrypted, signed, split into a series of 10MB chunks and uploaded into Amazon S3 for storage. An XML manifest file stores information about the AMI, including name, version, architecture, default kernel id, decryption key and digests for all of the filesystem chunks.
An AMI does not include a kernel image, only a pointer to the default kernel id, which can be chosen from an approved list of safe kernels maintained by Amazon and its partners (e.g., Red Hat, Canonical, Microsoft). Users may choose kernels other than the default when booting an AMI.
Operating systems 
When it launched in August 2006, the EC2 service offered Linux and later Sun Microsystems' OpenSolaris and Solaris Express Community Edition. In October 2008, EC2 added the Windows Server 2003 and Windows Server 2008 operating systems to the list of available operating systems. As of December 2010 it has also been reported to run FreeBSD; in March 2011, NetBSD AMIs became available.
Amazon Linux AMI 
Amazon has their own Linux distribution based on Red Hat Enterprise Linux and later linux-xen-kernel. Amazon has developed Amazon Linux AMI as a low cost offering. This offering has been in production since September 2011, and in development since 2010. The most recent release is version 2013.03 and utilizes version 3.4.37 of the Linux kernel, among other enhancements.
Types of images 
- Public: an AMI image that can be used by anyone.
- Paid: a for-pay AMI image that is registered with Amazon DevPay and can be used by any one who subscribes for it. DevPay allows developers to mark-up Amazon's usage fees and optionally add monthly subscription fees.
- Shared: a private AMI that can only be used by Amazon EC2 users who are allowed access to it by the developer.
- Amazon. "Amazon EC2 Functionality".
- Amazon. "Creating an Image".
- Feature Guide: Amazon EC2 User Selectable Kernels
- Shankland, Stephen (October 23, 2008). "Amazon's Linux cloud computing out of beta, joined by Windows". CNet News. Retrieved October 24, 2008.
- "Amazon Elastic Compute Cloud (EC2) Running Microsoft Windows Server and SQL Server". Amazon.com. October 23, 2008. Archived from the original on 1 December 2008. Retrieved October 25, 2008.
- Brockmeier, Joe (9 27, 2011). "Amazon's Linux AMI is All Grown Up". readwriteweb. Retrieved October 11, 2011.
- "Amazon Linux AMI - what distro is this based on?". Amazon web forums. 9 27, 2011. Retrieved October 11, 2011.
- "Amazon Linux AMI - 2011.09 release notes". Amazon. 9 27, 2011. Retrieved October 11, 2011.
- "Amazon Linux AMI - 2012.03 release notes". Amazon. 9 27, 2011. Retrieved October 11, 2011.
- "amazon-linux-ami 2012.03 packages". Amazon. 9 27, 2011. Retrieved October 11, 2011.
- "Updated List of Amazon Linux AMI’s". Jamie Begin. 2 28, 2013. Retrieved February 28, 2013.
- "Amazon Linux AMI 2013.03 Release Notes".
- Creating and preparing AMIs
- Amazon Web Services Developer Community : Amazon Machine Images (AMIs)
- Amazon Linux AMI