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  Amazon Machine Images (AMIs)

Speaking of images, AMI or Amazon Machine Image, that's what is used for launching your instances. This is one of the core concepts in Cloud Computing and this concept allows you to replicate the same data, the same environment, the same OS, everything. It allows you to replicate everything into multiple computers, not just in the same region, but in different regions and different data centers. That's how you build resiliency.

Let's talk more about the images. AMI can be converted to and from other image types. So, if you already have some images which work from different Cloud providers to different virtual environments, virtualization, hypervisor systems, there's a tool for that. Maybe you can just convert your images instead of rebuilding them from scratch. And then, one of the great things about AWS, it has the Marketplace. If you ever did any procurement, if you did any purchase orders for corporate enterprise software, you know it's a long cycle. There's a long contract and agreement process. There's many, many months before you can start actually using it. As a developer, that's not very effective using the marketplace, you can just use a certain software like Microsoft SQL or Oracle or maybe some Red Hat, paid Red Hat distribution. And from the marketplace, you would be just billed by hour without any complexity or any delays.

And obviously, you can create your own images, so that's why it's very powerful. There is no need to recreate all the steps over and over again. You just do it once and then you have an image. And all the subsequent instances of the replications, they're created from those images. One key to remember is that image ID, even if the image itself has all the same information, it could differ from region to region because regions they are pretty much separate, encapsulated environments when we talk about AWS.

AMIs could be backed by Elastic Block Storage or they could be backed by the instance Store. instance Store, it's very ephemeral. It pretty much dies. It disappears when you stab that instance and there is no status and run with an instance Store, so you can only terminate. And with the EBS, you can start and stop and the data would not disappear unless you delete that volume. What are the some of the OSs supported? One of the OS that we will be using is Amazon Linux. It's a special Amazon flavor of CentOS that's the image tab that we will be using most often during this course and it's especially optimized. So, it's nice to use the official image provided by AWS. Then there's also this technology, it's called HVM. A lot of the most recent modern images and recent versions, they will be supporting this HVM. It has something to do with the hardware, acceleration. So the recommended approach is to use images that support HVM.

And then, most of the images they have different versions, for example, 64 bit or 32 bit. So, 64 bits, it's the preferred format to use. And then, if you need some software like I mentioned, Oracle database or a WordPress or maybe some accounting software. You can get that software from the marketplace. Most of it would be paid, some of it would be open source, so you can use it community license, which is free. All that information is in the marketplace. We would be using during the lab, the version of WordPress. WordPress itself is an open source technology. So, we would be using an image which is free but it would have WordPress, MySQL, and PHP, and Apache server already installed.

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