A Comprehensive Guide on Amazon AMI (Amazon Machine Image)

What Is Amazon AMI?

An Amazon Machine Image is a special type of virtual machine that runs in the cloud. It is a master image that contains the information needed to launch instances (virtual servers) in the cloud. The virtual servers are known as EC2 instances in the AWS (Amazon Web Services) environment. An AMI serves as the basic deployment unit for services provided by EC2. 

Each AMI is configured with a template for the root volume needed for a specific type of instance. In a typical example, there might be an operating system, an application server and applications. Permission controls are in place to make sure that AMI launches stay restricted to the correct AWS accounts. One AMI can launch multiple instances if the configuration required for the instances is the same. But multiple AMIs are needed to launch instances with varying configurations.  

If there’s no AMI, there would be no instances, no method to define the parameters, and no way to run a web application, install an API, store a cloud database, or take any of the advantages of cloud computing. 

How to Create an AMI From an Amazon EC2 Instance? 

You can create AMIs using the Amazon EC2 instance using the following steps. 

1. Create an Amazon AMI from a running or stopped instance from the Amazon EC2 instances view. Right-click on the instances file and select ‘Create Image’.
2. A pop-up window will appear with fields that require information like name, description, etc. After entering the required information, select Create Image at the bottom of the window. The instance gets automatically shut down by Amazon EC2, which then takes a snapshot of all volumes attached, creates and registers the AMI and reboots the instance. 
3. It may take a few minutes for the AMI to be created. Once created, the AMI will appear in the AMI view of AWS Explorer. The AWS Explorer view can be accessed by double-clicking on Amazon EC2|AMIs node. To view AMIs, select Owned by Me from the Viewing drop-down menu. 
4. After an AMI is created and registered, you can use it to launch new instances. 

Searching for an AMI

Instances can be launched from AMIs not belonging to a user if the AMI owners have granted launch permissions. You can copy an AMI into the same or a different AWS region. Search for an AMI can be made either from the AWS, the user community or through the AWS CLI. 

Consider the following factors before choosing the appropriate AMI to suit your instance. 

• Region - Specify which region you want to search for an AMI from amongst the EC2 locations around the world.
• Architecture - Choose from 32-bit or 64-bit AMI architecture based on OS requirements.
• Operating System - Specify underlying Operating Systems like Linux.
• Launch Permissions - Look out for launch permissions from AMI owners, which can be either public, explicit, or implicit. 
• Storage for the root device - AMI storage option is provided by Amazon Elastic Block Store (EBS) and by instance store volume that is built from a template stored in Amazon S3.

Lifecycle of Amazon Machine Images

The AMI lifecycle consists of the following stages:

1. Create AMI with EBS snapshot or template if instance store is backed
2. Register AMI
3. Use AMI to Launch New Instances
4. Copy AMI to same or separate AWS regions
5. Deregister AMI when no longer required

Amazon Linux AMI Virtualization Types

There are 2 types of Amazon Linux AMI virtualization:

Paravirtualization – this type of virtualization improves the performance of guest OS by removing the overhead of emulating hardware and thorough knowledge about the guest OS. This technique is preferred for high-performance computing applications that require rapid processing like those used in scientific computing, transactional database, etc. there should be close cooperation between virtual machine monitor, guest OS, and modified OS kernel. 

Hardware Virtual Machines - Hardware Virtual Machines (HVM) are fully virtualized, and the underlying hardware needs to be emulated for the guests to use. With Paravirtualization (PV), on the other hand, no emulation is needed for the guest OS to run. With HVM, the host machine should have a specific feature available on its hardware. PV, however, requires the guest OS to have a specific feature present in the software. 

PV virtual machines are lightweight compared to HVM and hence boots faster and use less computer hardware. But they have a lesser number of operating systems. 

Buying, Selling, and Deregistering AMIs

Once an AMI is created, it can be kept private (meaning only the owner can use it) or can be shared with certain AWS accounts, or it can also be shared publicly with the community. For a shared AMI, the user can be at risk as Amazon does not guarantee the integrity or security of publicly shared AMIs. Users should perform their own diligence before using publicly available AMIs.

You can purchase AMIs from a third party like Red Hat, a Linux distribution that is based on Linux kernel source code. You can also sell your created AMIs to other Amazon EC2 users.

In case an AMI is deregistered, it cannot be used to launch new instances. Existing instances shall not be affected, however. An instance should be terminated once its use is finished. 

Best Practices for Building AMI

Some of the best practices to help you build an AMI are:

• Make sure you verify your AMI before submitting it. You can use self-service scanning for this purpose. 
• Always secure reselling rights for non-free Linux distributions, except AWS-provided Amazon Linux, SUSE, RHEL, Windows AMIs.
• Use the latest OS, packages and software to create AMIs
• Make sure your AMI adheres to all AWS Marketplace policies 
• Build products using current, well maintained AMIs that are supported by Amazon Elastic Block Store (Amazon EBS) and has a well-defined lifecycle from trusted sources like AWS Marketplace.
• Create an iterative process for building, updating and republishing AMIs
• Check port settings as:
• For Linux based AMIs – a valid SSH port should be open. The default port is 22.
• For Windows-based AMIs – the RDP port should be open. The default port is 3389. The default WinRM port 5985 should also be open to 10.0.0.0/16

Copying an AMI to Another AWS Region

For copying an AMI, you must create or obtain an AMI supported by an Amazon EBS snapshot. 

Here’s how you can copy an AMI using the console.

Step 1. Follow the link https://console.aws.amazon.com/ec2/ to open the Amazon EC2 console. 

Step 2. Use the console navigation bar to choose the Region that contains the AMI. Select Images AMIs to display the list of AMIs that are available in the chosen region.

Step 3. Select the AMI that you’re looking to copy. Choose Actions, Copy AMI.

Step 4. The Copy AMI dialogue box will open where you have to specify the requisite information and choose Copy AMI.

Benefits of Using AMI

The key benefits of using Amazon Machine Image (AMI) are:

• Faster set-up - AMI deployment is usually much faster and smoother compared to traditional software installations. There’s no manual installation, tedious configuration process or extra hardware requirements for the installation. 
• Pre-configured templates - Allow efficient deployment or one or more instances 
• Low cost - Another major benefit of AMI is the absence of upfront costs and the fact that you can deploy and configure it to suit your business needs. If you’re a small startup, you can deploy an instance for a simple mobile app, or you can pay more for higher usage in bigger projects. 
• Flexibility - An AMI can run Linux, UNIX or Windows and can also be supported with additional services. AMIs are compressed, secured and encrypted across all operating systems. 

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Conclusion 

We hope this deep dive into Amazon AMI has familiarized you with the concept. It’s a key skill in the current and evolving could computing landscape and one that will help you advance your career in the field. If you wish to learn more about Amazon AMI or add new cloud skills to your resume, a Cloud Computing Practitioner certification from Simplilearn is a great place to start. Sign up today to begin your journey towards becoming a successful cloud professional.